Conscious Rats Research Articles

Efficacy and safety of NAHAO® hydrogel in amelioration of chemoradiotherapy-induced oral mucositis: An preliminary clinical study (ChiCTR2200064766)

ObjectiveTo evaluate the efficacy of NAHAO® oral mucosal antibacterial care solution (NAHAO® spray) on attenuating oral mucositis (OM) symptoms and related mechanisms investigation. Material and methodsExperimental OM models were established by acetic acid and 5-fluorouracil combined with mechanical trauma. We investigated spontaneous pain of conscious OM rats after using NAHAO®. The expression of NF-κB in affected trigeminal ganglion was measured by western blot. In clinical study, 60 patients who developed post-treatment OM of grade 2 or above or persistent mucosal pain with a score equal to or greater than 4 points were selected. All patients were required to receive NAHAO® spray 8 times a day and were examined for OM degrees and oral mucosal pain scores before and after application. ResultsExperimental data from experimental model suggested that clinical efficacy of NAHAO® spray was involved in inflammation inhibition via NF-κB pathway. The results of clinical study showed that NAHAO® spray improved the symptoms of OM, there is statistically significant difference in oral mucosal pain scores after treated with NAHAO, and the dietary restrictions were also improved. ConclusionNAHAO® spray alleviates pain and improves the diet situation in OM patients, which is partly mediated through the inhibition of NF-κB pathway.

AT1-AA Infusion during Pregnancy Impairs CBF Autoregulation Postpartum.

Preeclampsia (PE), new-onset hypertension during pregnancy alongside organ dysfunction, is a leading cause of morbidity and mortality for the mother and fetus. PE women have activated B cells that produce agonistic autoantibodies to the angiotensin II type 1 receptor (AT1-AA). AT1-AA impairs cerebral blood flow (CBF) autoregulation during pregnancy. Although AT1-AA often remains elevated up to 8 years postpartum, AT1-AA's effect on CBF autoregulation postpartum is unknown. This study examined whether elevated AT1-AA during pregnancy impairs CBF autoregulation postpartum and if this was augmented by infusion of AT1-AA postpartum. AT1-AA was infused into 12-week-old timed-pregnant Sprague Dawley rats beginning on gestational day 14. Uterine artery resistance index (UARI) was measured on gestational day 18 as a measure of endothelial dysfunction associated with PE. Dams were allowed to deliver. One group was given a second infusion of AT1-AA (50% perinatal dose mimicking levels observed in postpartum PE women) at 9 weeks postpartum. After postpartum week 10, mean arterial pressure (MAP) was measured in conscious rats and CBF autoregulation was measured by laser Doppler flowmetry. AT1-AA during pregnancy increased UARI (P<0.05). AT1-AA during pregnancy did not affect MAP postpartum but did impair CBF autoregulation postpartum. Infusion of AT1-AA postpartum significantly elevated blood pressure (P<0.01) but did not further impair CBF autoregulation. This study demonstrates that circulating AT1-AA during pregnancy causes impairment of CBF autoregulation well into the postpartum period indicating that elevated AT1-AA leads to long-term cerebrovascular consequences. Targeting AT1-AA may prevent cerebrovascular effects associated with PE during pregnancy and postpartum.

Modulation of reflex responses of the anterior and posterior bellies of the digastric muscle in freely moving rats.

Chewing and licking are primarily activated by central pattern generator (CPG) neuronal circuits in the brainstem and when activated trigger repetitive rhythmic orofacial movements such as chewing, licking and swallowing. These CPGs are reported to modulate orofacial reflex responses in functions such as chewing. This study explored the modulation of reflex responses in the anterior and posterior bellies (ant-Dig and post-Dig, respectively) of the digastric muscle evoked by low-intensity trigeminal stimulation in conscious rats. The ant-Dig and post-Dig reflexes were evoked by using low-intensity electrical stimulation applied to either the right or left inferior alveolar nerve. Peak-to-peak amplitudes and onset latencies were measured. No difference was observed between threshold and onset latency for evoking ant-Dig and post-Dig reflexes, suggesting that the latter was also evoked disynaptically. The peak-to-peak amplitude of both reflexes was significantly reduced during chewing, licking and swallowing as compared to resting period and was lowest during the jaw-closing phase of chewing and licking. Onset latency was significantly largest during the jaw-closing phase. Inhibitory level was similar between the ant-Dig and post-Dig reflex responses and between the ipsilateral and contralateral sides. These results suggest that both the ant-Dig and post-Dig reflex responses were significantly inhibited, probably due to CPG activation during feeding behaviours to maintain coordination of jaw and hyoid movements and hence ensure smooth feeding mechanics.

Opposing effects of 5-HT1A receptor agonist buspirone on supraspinal abdominal pain transmission in normal and visceral hypersensitive rats.

The serotonergic 5-HT1A receptors are implicated in the central mechanisms of visceral pain, but their role in these processes is controversial. Considering existing evidences for organic inflammation-triggered neuroplastic changes in the brain serotonergic circuitry, the ambiguous contribution of 5-HT1A receptors to supraspinal control of visceral pain in normal and post-inflammatory conditions can be assumed. In this study performed on male Wistar rats, we used microelectrode recording of the caudal ventrolateral medulla (CVLM) neuron responses to colorectal distension (CRD) and electromyography recording of CRD-evoked visceromotor reactions (VMRs) to evaluate post-colitis changes in the effects of 5-HT1A agonist buspirone on supraspinal visceral nociceptive transmission. In rats recovered from trinitrobenzene sulfonic acid colitis, the CRD-induced CVLM neuronal excitation and VMRs were increased compared with those in healthy animals, revealing post-inflammatory intestinal hypersensitivity. Intravenous buspirone (2 and 4 mg/kg) under urethane anesthesia dose-dependently suppressed CVLM excitatory neuron responses to noxious CRD in healthy rats, but caused dose-independent increase in the already enhanced nociceptive activation of CVLM neurons in post-colitis animals, losing also its normally occurring faciliatory effect on CRD-evoked inhibitory medullary neurotransmission and suppressive action on hemodynamic reactions to CRD. In line with this, subcutaneous injection of buspirone (2 mg/kg) in conscious rats, which attenuated CRD-induced VMRs in controls, further increased VMRs in hypersensitive animals. The data obtained indicate a shift from anti- to pronociceptive contribution of 5-HT1A-dependent mechanisms to supraspinal transmission of visceral nociception in intestinal hypersensitivity conditions, arguing for the disutility of buspirone and possibly other 5-HT1A agonists for relieving post-inflammatory abdominal pain.

Vagal nerve activity and sympathetic nerve activity are suppressed by alpha-2 adrenergic receptor agonists in conscious rats

Vagal nerve activity (VNA) and sympathetic nerve activity (SNA) have been known to influence each other and changes in their activity directly, but details on this remain unknown. This study used an alpha-2 adrenergic receptor agonist (dexmedetomidine) to study how SNA affects VNA in the conscious state. Electroencephalography, electromyography, electrocardiography, cervical VNA, renal SNA, and catheters for arterial pressure measurement and intravenous drug administration were measured after male Wistar rats were anesthetized and implanted with electrodes. Dexmedetomidine (50 micro g/kg) was intravenously administered in conscious rats. Cervical VNA decreased and reached its lowest values about 10 min after intravenous dexmedetomidine administration. However, renal SNA, electromyography, and heart rate decreased immediately after administration, whereas arterial pressure increased immediately. These results show that alpha-2 adrenergic receptor agonists simultaneously inhibit VNA and SNA. Furthermore, the present data suggest that excessive SNA activation increases norepinephrine release, inducing an increase in the concentration of circulating norepinephrine, which in turn inhibits SNA via negative feedback and suppresses VNA. JST (JPMJMS2023) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A Kidney-Selective, Biopolymer-Delivered MMP-2 Inhibitory Peptide Protects Against Renal Injury in the Dahl Salt Sensitive Rat

Renal fibrosis, a hallmark of chronic kidney disease (CKD), is characterized by excessive deposition of extracellular matrix (ECM) components. Human and animal studies have shown that upregulation of the endopeptidase matrix metalloproteinase-2 (MMP-2) cleaves ECM and cytokines to promote inflammation and fibrosis in CKD. The objective of this study is to develop a novel, kidney-targeted MMP-2 inhibitor for prevention of renal fibrosis. Our group fused an MMP-2 inhibitory peptide (MMP-2i) to a kidney targeting biopolymer known as elastin like polypeptide (ELP). We previously optimized renal targeting of ELP-MMP-2i by testing the effect of ELP molecular weight on renal deposition and renal specificity, resulting in the selection of ELP 63 -MMP-2i (an ELP with 63 pentapeptide repeats and a molecular weight of 25 kDa) as a lead agent for continued therapeutic development. We also previously validated that ELP 63 -MMP-2i specifically inhibits MMP-2 without affecting other MMPs expressed in the kidney. The hypothesis of the current study is that our optimized agent, ELP 63 -MMP-2i, will ameliorate renal injury when administered to Dahl salt sensitive (Dahl S) rats fed a high-salt diet. To assess the efficacy of our therapeutic, 12-week-old Dahl S rats (male, n=4 per group) were fed a high salt (8% NaCl) diet and simultaneously dosed (300 nmol/kg/day s.c.) with either vehicle or ELP 63 -MMP-2i for 3 weeks. Metabolic cage housing was performed weekly to collect urine, blood pressure was assessed in conscious rats weekly by tail cuff plethysmography and at the experimental endpoint by direct measurement via an arterial catheter, and renal histology was assessed by Masson trichrome staining. Neither high-salt diet or ELP 63 -MMP-2i had any effect on the rats’ body weight. Blood pressure was elevated in Dahl S rats fed a high-salt diet (one-way ANOVA, F(2,19) time = 28.95, p&lt;0.0001), and ELP 63 -MMP-2i had no effect on the blood pressure elevation (F(2,9) treatment = 0.03, p=0.97). Proteinuria was also significantly and progressively elevated during the high-salt feeding period (F(2,19) time = 15.61, p&lt;0.0001). ELP 63 -MMP-2i treatment reduced the severity of proteinuria (F(2,9) treatment = 5.02, p=0.03). We also observed significant renal fibrosis in Dahl S rats after 21 days of high-salt diet, and that there was a trend for reduced fibrosis in the renal cortex in rats treated with ELP 63 -MMP-2i compared to vehicle (paired t-test, p=0.11). These are intermediate findings of an ongoing study with a planned enrollment of 8 rats per group. The intermediate analysis suggests that inhibiting MMP-2 activity with an MMP-2 specific and renally targeted biologic is renoprotective and may be beneficial as a treatment for CKD. This work was supported by NIH grants R01HL095638 to GLB, R01HL138685 to RJR and F31DK130598 to AAA. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The “forgotten circulation”: Sympathetic control of mesenteric venous capacity in conscious hypertensive rats

The venous circulation is often “forgotten,” as cardiovascular research and therapeutic intervention focusses predominantly on arteries. However, systemic veins store two-thirds of blood volume at rest, with reservoir beds such as the mesenteric circulation receiving dense sympathetic innervation, suggesting a critical neurogenic role for the mobilization of blood. The impact of hypertension on sympathetic regulation of venous circulation remains unclear. We hypothesized that capacity of mesenteric vasculature is impaired in spontaneously hypertensive rats (SHR) and that reducing sympathetic drive will increase mesenteric buffering of excess volume.SHR (n=6) and Wistar rats (n=7) were instrumented with telemeters recording arterial and venous pressures, and an atrial balloon for assessment of mean circulatory filling pressure (MCFP). Arterial (inflow) and venous (outflow) mesenteric flow probes were implanted to measure total mesenteric volume fluctuation. Mesenteric vascular capacity was challenged with 20% volume load of intravenous saline. In SHR sympathetic drive was reduced via hexamethonium (10mg/kg) or via carotid body denervation (CBD).MCFP was elevated in SHR (+2.7±0.5mmHg, p&lt;0.01 vs Wistars). MCFP in SHR was reduced by hexamethonium (-2.6±0.6; p=0.01 vs Baseline, n=5) and CBD (‑2.0±0.7mmHg; p=0.04 vs Baseline, n=5). In normotensives volume load was accommodated by the mesenteric bed, with a net total influx of blood (+5.4±2.2ml; n=7). In contrast, SHR showed a counter-intuitive net efflux of blood from the mesenteric bed (-1.6±1.4ml; p=0.04 vs Wistars, n=6). Preliminary results indicate that hexamethonium and CBD tended to increase the ability of the mesenteric bed to accommodate volume (hexamethonium: +1.9±1.5, n=6; CBD: +0.8±0.6ml, n=3).We show that SHR have higher venous tone and reduced capacity to accommodate excess volume within the mesenteric vascular bed. Reductions in sympathetic drive reduced venous tone and improved the ability to accommodate volume load. Inhibiting sympathetic activity may provide a novel therapeutic opportunity to restore venous mesenteric capacity and potentially ameliorate hypertension. Marsden Fund, Royal Society of New Zealand; Health Research Council of New Zealand This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The effects of excess salt intake on the kidney metabolism in normal Sprague Dawley rats.

Introduction: This study aimed to determine the effects of a high salt diet upon the metabolism of O 2 and substances in the kidney in normal Sprague Dawley (SD) rats. Methods were developed enabling the intermittent collection of renal arteriovenous (A-Vr) blood and urine samples and to measure renal blood flow (RBF) and arterial pressure (BP) in conscious freely moving rats with GFR determined in a separate group of conscious rats. Other groups were studied to obtain cortical (Cx) and outer medullary (OM) tissue samples for associated transcriptomic and metabolomic profiles. Methods: SD rats were instrumented with a renal arterial ultrasonic flow probe, a femoral arterial and renal venous catheters, and RBF and BP measured continuously (24/7). Arterial (A) and renal venous (Vr) blood and urine were collected repeatedly before and 7, 14, and 21 days after increasing the salt diet from 0.4% (LS) to 4% (HS) NaCl. GFR was measured in age-matched rats and used as control shams for normalization. Blood O 2 content was determined by radiometry. A global metabolomic analysis was performed on plasma and Cx and OM tissue samples at JAX laboratories (Thermo Q-Exactive Orbitrap coupled to Vanquich UPLC system) and together with mRNAseq analysis for Cx and OM by Novogene Inc. Results: BP increased less than 5 mmHg by day 3 of the HS diet while RBF rose nearly 20% (P&lt;0.05) and both were sustained at this level throughout the study. O 2 delivery, O 2 consumption (VO 2 ) and O 2 extraction rose over the 21 days of the HS diet (P&lt;0.05). Total GFR increased from 0.64 to 0.83 mL/min/100 g bw (P&lt;0.05) at HS 7 and remained elevated at HS 21. Whole kidney Na + reabsorption and kidney VO 2 were highly correlated positively (r=0.99). A sparse partial least squares discriminant analysis (sPLS-DA) of metabolomics for each of the 4 modes (C18 +/- and HILIC +/-) revealed clear distinctions between LS, HS14, and HS21 within Cx and OM. The mRNAseq tissue analysis found that the HS diet resulted in reduced expression of genes related to the TCA cycle and metabolism of amino acids and fatty acids. This was consistent with the metabolomic data showing a reduction of tissue citrate and succinate levels. In contrast, glycolysis-related genes including hexokinase, pyruvate kinase and lactate dehydrogenase were upregulated in the Cx tissue by HS. Minimal changes in metabolic pathways were observed in the OM tissue. A-Vr x RBF enabled metabolomic flux determination which showed the release of glucose on LS fed rats which was not evident with the HS diet. Uptake of citrate which was seen on LS was less evident on HS but there was a clear tendency observed for increased release of lactate, pyruvate, and α-ketoglutarate. Conclusions: Normal SD rats fed a HS underwent changes of RBF, O 2 extraction and utilization of metabolic substrates, most notably transitioning ATP production predominantly driven from TCA cycle to non-TCA cycle pathways which we are currently exploring more deeply. HL-116264, HL-151587 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Chronic Effects of Apelin on Cardiovascular Regulation and Angiotensin II-Induced Hypertension.

Apelin, by stimulation of APJ receptors, induces transient blood pressure (BP) reduction and positive inotropic effects. APJ receptors share high homology with the Ang II type 1 receptor; thus, apelin was proposed to play a protective role in cardiovascular disease by antagonizing the actions of Ang II. In this regard, apelin and apelin-mimetics are currently being studied in clinical trials. However, the chronic effect of apelin in cardiovascular regulation has not been fully investigated. In the current study, blood pressure (BP) and heart rate (HR) were recorded using a telemetry implantation approach in conscious rats, before and during chronic subcutaneous infusion of apelin-13, using osmotic minipumps. At the end of the recording, the cardiac myocyte morphology was examined using H&E staining, and cardiac fibrosis was evaluated by Sirius Red in each group of rats. The results demonstrated that the chronic infusion of apelin-13 did not change either BP or HR. However, under the same condition, the chronic infusion of Ang II induced significant BP elevation, cardiac hypertrophy, and fibrosis. Co-administration of apelin-13 did not significantly alter the Ang II-induced elevation in BP, changes in cardiac morphology, and fibrosis. Taken together, our experiments showed an unexpected result indicating that the chronic administration of apelin-13 did not alter basal BP, nor did it change Ang II-induced hypertension and cardiac hypertrophy. The findings suggest that an APJ receptor biased agonist could be a better therapeutic alternative for treatment of hypertension.

Involvement of acid sensing ion channel (ASIC)-3 in an acute urinary bladder-colon cross sensitization model in rodent.

Irritable bowel syndrome and bladder pain syndrome are both characterized by pain in response to organ distension. Epidemiologic studies showed that these two syndromes are often overlapped. Such overlap may be due to sharing of common extrinsic innervations between the colorectum and the urinary bladder, where cross-sensitization of the urinary bladder and the colon would occur in response to mechanical distension of either organ. The aim of this project was to develop and characterize a rodent model of urinary bladder-colon sensitization and to assess the role of the acid sensing ion channel (ASIC)-3. Double retrograde labelling was performed to identify extrinsic primary afferent neurons innervating both the colon (Fluororuby) and urinary bladder (Fluorogold) in the L6-S1 dorsal root ganglia (DRG) in Sprague Dawley rats. The phenotype of the colon/urinary bladder co-innervating primary afferent neurons was assessed using immunohistochemistry directed against ASIC-3. Cross-organ sensitization was induced in Sprague Dawley rats by using an echography-guided intravesical administration of acetic acid (0.75%) under brief isoflurane anesthesia. Colonic sensitivity was assessed in conscious rats by measuring abdominal contraction during isobaric colorectal distension (CRD). Measurement of urinary bladder and colonic paracellular permeabilities and tissue myeloperoxidase assay were performed. The involvement of ASIC-3 was assessed by use of S1 intrathecal administration of the ASIC-3 blocker, APETx2 (2.2 µM). Immunohistochemistry showed that 73.1% of extrinsic primary afferent neurons co-innervating the colon and the urinary bladder express ASIC-3. By contrast, extrinsic primary afferent neurons innervating the colon only or the urinary bladder only were positive for ASIC-3 in 39.3% and 42.6%, respectively. Echography-guided intravesical administration of acetic acid resulted in colonic hypersensitivity to colorectal distension. This effect started 1 h post-injection and lasted up to 24 h, and was not longer seen after 3 days after injection. No colonic hyperpermeability and no difference in urinary bladder and colon MPO activity was observed between control and acetic acid-treated rats. Colonic sensitization by intravesical acetic acid administration was prevented by S1 intrathecal administration of APETx2. We developed an acute pelvic cross-organ sensitization model in conscious rat. In this model, cross-organ sensitization is likely to involve S1-L6 extrinsic primary afferents co-innervating the colon and urinary bladder through an ASIC-3 pathway.

ESTROGEN ALLEVIATES POSTHEMORRHAGIC SHOCK MESENTERIC LYMPH-MEDIATED LUNG INJURY THROUGH AUTOPHAGY INHIBITION.

Background: Hemorrhagic shock-induced acute lung injury (ALI) is commonly associated with the posthemorrhagic shock mesenteric lymph (PHSML) return. Whether excessive autophagy is involved in PHSML-mediated ALI remains unclear. The relationship between estrogen treatment and PHSML or autophagy needs to verify. The current study will clarify the role of estrogen in reducing PHSML-mediated ALI through inhibition of autophagy. Methods: First, a hemorrhagic shock model in conscious rats was used to observe the effects of 17β-estradiol (E2) on intestinal blood flow, pulmonary function, intestinal and pulmonary morphology, and expression of autophagy marker proteins. Meanwhile, the effect of PHSML and autophagy agonist during E2 treatment was also investigated. Secondly, rat primary pulmonary microvascular endothelial cells were used to observe the effect of PHSML, PHSML plus E2, and E2-PHSML (PHSML obtained from rats treated by E2) on the cell viability. Results: Hemorrhagic shock induced intestinal and pulmonary tissue damage and increased wet/dry ratio, reduced intestinal blood flow, along with pulmonary dysfunction characterized by increased functional residual capacity and lung resistance and decreased inspiratory capacity and peak expiratory flow. Hemorrhagic shock also enhanced the autophagy levels in intestinal and pulmonary tissue, which was characterized by increased expressions of LC3 II/I and Beclin-1 and decreased expression of p62. E2 treatment significantly attenuated these adverse changes after hemorrhagic shock, which was reversed by PHSML or rapamycin administration. Importantly, PHSML incubation decreased the viability of pulmonary microvascular endothelial cells, while E2 coincubation or E2-treated lymph counteracted the adverse roles of PHSML. Conclusions: The role of estrogen reducing PHSML-mediated ALI is associated with the inhibition of autophagy.

Drug Candidate BGP-15 Prevents Isoproterenol-Induced Arrhythmias and Alters Heart Rate Variability (HRV) in Telemetry-Implanted Rats.

Multi-target drug candidate BGP-15 has shown cardioprotective and antiarrhythmic actions in diseased models. Here, we investigated the effects of BGP-15 on ECG and echocardiographic parameters, heart rate variability (HRV), and arrhythmia incidence in telemetry-implanted rats, under beta-adrenergic stimulation by isoproterenol (ISO). In total, 40 rats were implanted with radiotelemetry transmitters. First, dose escalation studies (40-160 mg/kg BGP-15), ECG parameters, and 24 h HRV parameters were assessed. After, rats were divided into Control, Control+BGP-15, ISO, and ISO+BGP-15 subgroups for 2 weeks. ECG recordings were obtained from conscious rats, arrhythmias and HRV parameters were assessed, and echocardiography was carried out. ISO-BGP-15 interaction was also evaluated on an isolated canine cardiomyocyte model. BGP-15 had no observable effects on the ECG waveforms; however, it decreased heart rate. HRV monitoring showed that BGP-15 increased RMSSD, SD1, and HF% parameters. BGP-15 failed to counteract 1 mg/kg ISO-induced tachycardia, but diminished the ECG of ischemia and suppressed ventricular arrhythmia incidence. Under echocardiography, after low-dose ISO injection, BGP-15 administration lowered HR and atrial velocities, and increased end-diastolic volume and ventricle relaxation, but did not counteract the positive inotropic effects of ISO. Two weeks of BGP-15 treatment also improved diastolic function in ISO-treated rats. In isolated cardiomyocytes, BGP-15 prevented 100 nM ISO-induced aftercontractions. Here, we show that BGP-15 increases vagally mediated HRV, reduces arrhythmogenesis, enhances left ventricle relaxation, and suppresses the aftercontractions of cardiomyocytes. As the drug is well tolerated, it may have a clinical value in preventing fatal arrhythmias.

Dietary Fish Oil Does Not Alter Glucose Tolerance in Conscious Rats

We examined the effect of dietary fish oil (MaxEPA) and sunflower seed oil on glucose tolerance in male Wistar rats. Semipurified diets containing 100 g oil/kg diet were administered for 30 d. The fish oil diet contained 26 g (n-3) fatty acids, 16 g eicosapentaenoic acid and 10.4 g docosahexaenoic acid/kg diet. Phospholipids from liver, pancreas, and pancreatic islets were enriched in eicosapentaenoic and docosahexaenoic acids by the fish oil diet. In unfed pentobarbital-anesthetized rats, both basal plasma insulin concentration and insulin responses to intravenous glucose were significantly lower for fish oil-fed rats although glucose responses were similar; however, incremental excursions in plasma insulin over the basal concentrations did not differ. Intravenous glucose tolerance was also examined in conscious unfed rats under minimal restraint. Responses of plasma glucose and insulin were similar for fish oil- and sunflower oil-fed groups. Furthermore, in another experiment, intravenous glucose tolerance tests were similar for conscious rats provided with either 100 g fish oil or corn oil/kg nonpurified diet. Thus, glucose-induced insulin secretion is lower in rats fed fish oil than in rats fed sunflower oil, when tests are conducted in pentobarbital-anesthetized animals but not when tests are performed in conscious rats; there was no effect on plasma glucose in either anesthetized or nonanesthetized rats. Therefore, substitution of (n-3) for (n-6) polyunsaturated fatty acids in tissue phospholipids does not alter plasma glucose or insulin in conscious male Wistar rats.

Standard procedures for blood withdrawal in conscious male rats induce stress and profoundly affect glucose tolerance and secretion of glucoregulatory hormones

ObjectiveA fundamental difference between physiological and pharmacological studies in rats and humans is that withdrawal of blood from conscious rats necessitates restraint which inevitably inflicts a higher level of stress. We investigated the impact of handling on acute glucose regulation and secretion of glucoregulatory hormones in rats. MethodsFasted male Sprague Dawley rats (375–400 g, n = 11) were given an oral glucose tolerance test (OGTT) by gavage (2 g/kg). Blood was sampled frequently until 90 min after challenge by handheld sampling (HS) or by automated sampling (AS). In the HS experiment, blood was withdrawn by restraint and sublingual vein puncture; two weeks later, samples were obtained by AS through an implanted catheter in a carotid artery, allowing sampling without disturbing the animals. ResultsOn the day of HS, post challenge glucose AUCs were ∼17% higher (P < 0.0001), despite gastric emptying (AUC) being reduced by ∼30% (P < 0.0001). Plasma insulin AUC was 3.5-fold lower (P < 0.001), and glucose-dependent insulinotropic peptide (GIP) AUC was reduced by ∼36% but glucagon-like peptide-1 concentrations were not affected. Glucagon concentrations were higher both before and after challenge (fold difference in AUCs = 3.3). Adrenocorticotropin (ACTH) and corticosterone AUCs were 2.4-fold and 3.6-fold higher (P < 0.001), respectively. Discussion and conclusionOur study highlights that sampling of blood from conscious rats by sublingual vein puncture inflicts stress which reduces glucose absorption and glucose tolerance and blunts secretion of insulin and GIP. As blood sampling in humans are less stressful, standard procedures of conducting OGTT's in rats by HS presumably introduce an interspecies difference that may have negative consequences for translatability of test results.

Embolic occlusion of internal carotid artery in conscious rats: Immediate effects of cerebral ischemia.

In most preclinical models of focal ischemic stroke, vascular occlusion is performed under general anesthesia. However, anesthetic agents exert confounding effects on mean arterial blood pressure (MABP), cerebrovascular tone, oxygen demand, and neurotransmitter receptor transduction. Moreover, the majority of studies do not use a blood clot, which more fully models embolic stroke. Here, we developed a blood clot injection model to produce large cerebral artery ischemia in unanesthetized rats. Under isoflurane anesthesia, an indwelling catheter was implanted in the internal carotid artery via a common carotid arteriotomy and preloaded with a 0.38-mm-diameter clot of 1.5, 3, or 6cm length. After discontinuing anesthesia, the rat was returned to a home cage where it regained normal mobility, grooming, eating activity, and a stable recovery of MABP. One hour later, the clot was injected over a 10-s period and the rats were observed for 24 h. Clot injection produced a brief period of irritability, then 15-20 min of complete inactivity, followed by lethargic activity at 20-40 min, ipsilateral deviation of the head and neck at 1-2h, and limb weakness and circling at 2-4h. Neurologic deficits, elevated MABP, infarct volume, and increased hemisphere water content varied directly with clot size. Mortality after 6-cm clot injection (53%) was greater than that after 1.5-cm (10%) or 3-cm (20%) injection. Combined non-survivor groups had the greatest MABP, infarct volume, and water content. Among all groups, the pressor response correlated with infarct volume. The coefficient of variation of infarct volume with the 3-cm clot was less than that in published studies with the filament or standard clot models, and therefore may provide stronger statistical power for stroke translational studies. The more severe outcomes from the 6-cm clot model may be useful for the study of malignant stroke.

A portable feedback-controlled pump for monitoring eye outflow facility in conscious rats.

Intraocular pressure (IOP) is heavily influenced by the resistance of trabecular outflow pathways through which most of the aqueous humor produced by the eye continuously drains. The standard method of quantifying outflow resistance and other aspects of ocular fluid dynamics is eye cannulation, which allows for direct measurement and manipulation of IOP and flow in animal models. Since the method is invasive, indirect techniques that are slower and less accurate must be used for chronological studies. A novel technology is introduced that can autonomously measure outflow facility in conscious rats multiple times a day. A smart portable micropump infuses fluid into the eye through a permanently-implanted cannula and dynamically adjusts flow rate using a unique proportional feedback algorithm that sets IOP to a target level, even though IOP fluctuates erratically in awake free-moving animals. Pressure-flow data collected by the system from anesthetized rats were validated against intraocular recordings with commercial pressure and flow sensors. System and sensor estimates of outflow facility were indistinguishable, averaging 23 ± 3 nl·min-1·mmHg-1 across animals (n = 11). Pressure-flow data were then collected round-the-clock for several days from conscious rats, while outflow facility was measured every few hours. A significant diurnal facility rhythm was observed in every animal (n = 4), with mean daytime level of 22 ± 10 nl·min-1·mmHg-1 and mean nighttime level of 15 ± 7 nl·min-1·mmHg-1. The rhythm correlated with diurnal changes in IOP and likely contributed prominently to those changes based on the day-night swing in facility magnitude. Hence, the portable smart pump offers a unique tool for repeated long-term monitoring of outflow facility and other possible parameters of ocular health. It could also be useful in animal glaucoma studies for reversibly inducing acute or chronic ocular hypertension without explicitly damaging trabecular outflow pathways.

PS-BPC06-5: EXOGENOUS THYROXINE INCREASES GLUT4 TRANSLOCATION IN MEMBRANE AND IMPROVES CARDIAC METABOLISM INDEPENDENT OF REDUCED SBP IN INSULIN RESISTANT OLETF RATS

Objective: During insulin resistance the heart undergoes a metabolic shift where fatty acids (FA) account for about 99% of the ATP production, indicative of impaired glucose metabolism. This results in increased reactive oxygen species and lipotoxicity leading to impaired mitochondrial function. Thyroid disorders such as hyperthyroidism and hypothyroidism both have the potential to lead to hypertension. Thyroid hormones (TH) may improve glucose intolerance by increasing glucose reabsorption and metabolism and therefore improve cardiac function and lower the risk of developing hypertension. However, incongruent data exists showing that TH promote oxidative stress and cardiac hypertrophy. Thus, the beneficial effects of TH in the heart during insulin resistance remains controversial. The glucose transport protein, GLUT4, is a downstream target of the TH response element indicating a possible mechanism by which TH regulate glucose metabolism. Design: Insulin resistant, Otsuka Long Evans Tokushima Fatty (OLETF) rats were used to assess the effects of exogenous thyroxine (T4) on glucose metabolism in cardiac tissue. Rats were assigned to four groups: 1) lean, Long Evans Tokushima Otsuka (LETO; n = 6), 2) LETO + T4 (8 μg/100 g BM/d × 5 wks; n = 7), 3) untreated OLETF (n = 6), and 4) OLETF + T4 (n = 7). T4 was administered via osmotic minipumps implanted subcutaneously. Systolic blood pressure (SBP) was measured weekly in conscious rats by tail-cuff plethysmography. Animals were provided water and food ad libitum. Results: SBP increased by 15% in OLETF compared to lean LETO (138 ± 2 vs. 117 ± 1 mm Hg), but T4 did not alter SBP is OLETF strain. T4 increased GLUT4 gene expression by 85% and GLUT4 protein translocation to the membrane by 328% in OLETF. Additionally, T4 increased phosphofructokinase-1, the rate limiting step in glycolysis, by 98% and decreased CD36 gene expression for FA transport by 20% in OLETF. We expect our recent metabolomics and lipidomics data to help better explain these molecular changes. Conclusions: Five-week dose of exogenous T4 did not reduce SBP is OLETF. The results suggest that increased T4 has the potential to increase glucose reabsorption and metabolism in the heart of insulin resistant rats and restore impaired substrate metabolism, but these improvements in substrate metabolism do not translate to sustained reduction in arterial pressure.

Modulation of Digastric Reflex Responses during Chewing, Licking and Swallowing in conscious rats

Modulation of Digastric Reflex Responses during Chewing, Licking and Swallowing in conscious rats

Effects of extremity trauma on physiological responses to hemorrhage in conscious rats.

Although physiological responses to hemorrhage are well-studied, hemorrhage is often accompanied by trauma, and it remains unclear how injury affects these responses. This study examined effects of extremity trauma on cardiorespiratory responses and survival to moderate (37%; H-37) or severe (50%; H-50) hemorrhage in rats. Transmitter and carotid catheter implantation and extremity trauma (fibular fracture and muscle injury) were conducted 2 wk, 24 h, and 90 min, respectively, before conscious hemorrhage. Mean arterial pressure (MAP) and heart rate (HR; via telemetry), and respiration rate (RR), minute volume (MV), and tidal volume (TV; via plethysmography) were measured throughout the 25 min hemorrhage and remainder of the 4 h observation period. There were four groups: 1) H-37, no trauma (NT; n = 17); 2) H-37, extremity trauma (T, n = 18); 3) H-50, NT (n = 20); and 4) H-50, T (n = 20). For H-37, during and after hemorrhage, T increased HR (P ≤ 0.031) and MV (P ≤ 0.048) compared with NT rats. During H-50, T increased HR (0.041) and MV (P = 0.043). After hemorrhage, T increased MV (P = 0.008) but decreased HR (P = 0.007) and MAP (P = 0.039). All cardiorespiratory differences between T and NT groups were intermittent. Importantly, both survival time (159.8 ± 78.2 min vs. 211.9 ± 60.3 min; P = 0.022; mean ± SD) and percent survival (45% vs. 80%; P = 0.048) were less in T versus NT rats after H-50. Trauma interacts with physiological systems in a complex manner and no single cardiorespiratory measure was sufficiently altered to indicate that it alone could account for increased mortality after H-50.NEW & NOTEWORTHY In both civilian and military settings, severe hemorrhage rarely occurs in the absence of tissue trauma, yet many animal models for the study of hemorrhage do not include significant tissue trauma. This study using conscious unrestrained rats clearly demonstrates that extremity trauma worsens the probability of survival after a severe hemorrhage. Although no single cardiorespiratory factor accounted for the increased mortality, multiple modest time-related cardiorespiratory responses to the trauma were observed suggesting that their combined dysfunction may have contributed to the reduced survival.

Piezo1-pannexin-1-P2X3 axis in odontoblasts and neurons mediates sensory transduction in dentinal sensitivity.

According to the "hydrodynamic theory," dentinal pain or sensitivity is caused by dentinal fluid movement following the application of various stimuli to the dentin surface. Recent convergent evidence in Vitro has shown that plasma membrane deformation, mimicking dentinal fluid movement, activates mechanosensitive transient receptor potential (TRP)/Piezo channels in odontoblasts, with the Ca2+ signal eliciting the release of ATP from pannexin-1 (PANX-1). The released ATP activates the P2X3 receptor, which generates and propagates action potentials in the intradental Aδ afferent neurons. Thus, odontoblasts act as sensory receptor cells, and odontoblast-neuron signal communication established by the TRP/Piezo channel-PANX-1-P2X3 receptor complex may describe the mechanism of the sensory transduction sequence for dentinal sensitivity. To determine whether odontoblast-neuron communication and odontoblasts acting as sensory receptors are essential for generating dentinal pain, we evaluated nociceptive scores by analyzing behaviors evoked by dentinal sensitivity in conscious Wistar rats and Cre-mediated transgenic mouse models. In the dentin-exposed group, treatment with a bonding agent on the dentin surface, as well as systemic administration of A-317491 (P2X3 receptor antagonist), mefloquine and 10PANX (non-selective and selective PANX-1 antagonists), GsMTx-4 (selective Piezo1 channel antagonist), and HC-030031 (selective TRPA1 channel antagonist), but not HC-070 (selective TRPC5 channel antagonist), significantly reduced nociceptive scores following cold water (0.1ml) stimulation of the exposed dentin surface of the incisors compared to the scores of rats without local or systemic treatment. When we applied cold water stimulation to the exposed dentin surface of the lower first molar, nociceptive scores in the rats with systemic administration of A-317491, 10PANX, and GsMTx-4 were significantly reduced compared to those in the rats without systemic treatment. Dentin-exposed mice, with somatic odontoblast-specific depletion, also showed significant reduction in the nociceptive scores compared to those of Cre-mediated transgenic mice, which did not show any type of cell deletion, including odontoblasts. In the odontoblast-eliminated mice, P2X3 receptor-positive A-neurons were morphologically intact. These results indicate that neurotransmission between odontoblasts and neurons mediated by the Piezo1/TRPA1-pannexin-1-P2X3 receptor axis is necessary for the development of dentinal pain. In addition, odontoblasts are necessary for sensory transduction to generate dentinal sensitivity as mechanosensory receptor cells.