Pentobarbital Anesthesia Research Articles

Cardiac Vagal Afferent Response in Rats during Cardiac Contractility Modulation (CCM)

Congestive heart failure (CHF) is responsible for substantial cardiac morbidity and mortality. Cardiac Contractility Modulation (CCM) delivers non‐excitatory endocardial electrical pulses during the refractory period. CCM enhances cardiac contractility, ejection fraction, and quality of life in patients. The underlying mechanism of action for these benefits is not fully understood. Since similar impulses delivered to the gut increase muscle contraction leading to activation of vagal afferents, we tested the effect of CCM on vagal afferent activity in the heart.HypothesisCCM results in an increase in activity of cardiac vagal afferent nerves. Since CCM is non‐excitatory, we speculate that CCM reflexly activates vagal afferents via increases in contractility, reducing excessive efferent sympathetic tone in CHF.MethodsAdult male Sprague‐Dawley rats under pentobarbital anesthesia were instrumented for extracellular recordings of cardiac vagal afferent firing during CCM stimulation of the left ventricle (4V or 7.5V for 60s).ResultsIn 18 vagal nerve fibers with cardiac receptive fields, CCM produced an intensity dependent increase (p<0.05) in firing frequency of 10 fibers (4.2 ± 1.2 Hz at 7.5V vs. 1.4 ± 0.66 Hz at baseline). 6 neurons were not affected by CCM. In two neurons, 4V stimulation increased while 7.5V had no effect on single fiber firing.ConclusionCCM, a new therapy for CHF elicits activation of cardiac vagal afferents. This likely results from a reflex increase in regional contractility, contributing to the clinical benefit of CCM via an increase in vagal afferent and reduced sympathetic tone. Supported by Impulse Dynamics, Inc.

Pentobarbital anaesthesia in the chronobiological studies

Administration of anaesthesia may influence specific aspects of in vivo animal experiments and is an especially important consideration for experiments conducted during the daytime. Although chronobiological studies investigating interactions between general anaesthesia and circadian rhythms are sparse, all suggest that general anaesthetic agents have a significant effect on circadian rhythms. To assess the suitability of pentobarbital anaesthesia in chronobiological studies, this study was performed using pentobarbital-anaesthetized (40 mg/kg, intraperitoneal) female Wistar rats after adaptation to a light–dark (LD) cycle (12 h:12 h). Heart rate, rectal temperature (RT), electrocardiographic parameters, autonomic nervous system activity, acid–base balance and plasma concentrations of Na+, K+, Ca2+ and Cl- were evaluated for their dependence on the LD cycle. LD differences were found in heart rate and RT, measured before the administration of the anaesthetic agent. Pentobarbital anaesthesia eliminated LD differences in all electrophysiological parameters, parameters of heart rate variability (except RR intervals) and parameters of acid–base balance and ion concentrations. LD differences with borderline statistical significance were found only for Na+ levels, with a higher level in the light period (i.e. nonactive) of the rat regimen day. During pentobarbital anaesthesia, parasympathetic tone predominates and sympathetic activity is depressed. Spontaneously breathing rats under pentobarbital anaesthesia are in an asphyxic state independent of the LD cycle in in vivo experiments. Results of this study suggest that pentobarbital anaesthesia is not suitable for chronobiological studies. However, it is suitable for cardiovascular research that is done regardless of the circadian rhythmicity, because it does not cause significant changes in heart activity.

Effects of anesthetics pentobarbital sodium and chloral hydrate on urine proteome.

Urine can be a better source than blood for biomarker discovery since it accumulates many changes. The urine proteome is susceptible to many factors, including anesthesia. Pentobarbital sodium and chloral hydrate are commonly used anesthetics in animal experiments. This study demonstrated the effects of these two anesthetics on the rat urine proteome using liquid chromatography–tandem mass spectrometry (LC-MS/MS). With anesthesia, the urinary protein-to-creatinine ratio of all rats increased twofold. The relative abundance of 22 and 23 urinary proteins were changed with pentobarbital sodium or chloral hydrate anesthesia, respectively, as determined by label-free quantification. Among these changed proteins, fifteen had been considered as candidate biomarkers such as uromodulin, and sixteen had been considered stable in healthy human urine, which are more likely to be considered as potential biomarkers when changed, such as transferrin. The pattern of changed urinary proteins provides clues to the discovery of urinary proteins regulatory mechanisms. When determining a candidate biomarker, anesthetic-related effects can be excluded from future biomarker discovery studies. Since anesthetics take effects via nervous system, this study is the first to provide clues that the protein handling function of the kidney may possibly be regulated by the nervous system.

Contralateral Metabolic Activation Related to Plastic Changes in the Spinal Cord after Peripheral Nerve Injury in Rats

We have previously reported the crossed-withdrawal reflex in which the rats with nerve injury developed behavioral pain responses of the injured paw to stimuli applied to the contralateral uninjured paw. This reflex indicates that contralateral plastic changes may occur in the spinal cord after unilateral nerve injury. The present study was performed to elucidate the mechanisms and morphological correlates underlying the crossed-withdrawal reflex by using quantitative 14C-2-deoxyglucose (2-DG) autoradiography which can examine metabolic activities and spatial patterns simultaneously. Under pentobarbital anesthesia, rats were subjected to unilateral nerve injury. Mechanical allodynia was tested for two weeks after nerve injury. After nerve injury, neuropathic pain behaviors developed progressively. The crossed-withdrawal reflex was observed at two weeks postoperatively. Contralateral enhancement of 2-DG uptake in the ventral horn of the spinal cord to electrical stimulation of the uninjured paw was observed. These results suggest that the facilitation of information processing from the uninjured side to the injured side may contribute to the crossed-withdrawal reflex by plastic changes in the spinal cord of nerve-injured rats.

Monitoring Motions in GABA-A Receptor Intersubunit Transmembrane Cavities

GABA-A receptors (GABAARs) are the target for many therapeutic drugs including benzodiazepines (BZDs), barbiturates, anesthetics and neurosteroids. These drugs bind to distinct sites and potentiate GABA-induced currents. They are often used in combination but little is known about mechanism(s) underlying their interactions. Recent crystal structures of GLIC and the glutamate-activated chloride channel suggest agonist-mediated channel opening is associated with expansion of transmembrane interfaces between M3 and M1 helices of adjacent subunits. Here, we examined if binding of different allosteric drugs and combinations of these drugs to α1β2γ2L GABAARs induce similar motions. We also tested whether potentiation of GABA-mediated current by pairs of drugs binding to distinct sites are additive or super-additive.We individually inserted a cysteine in the M1 helices of each GABAAR subunit at α1I227, β2L223 and γ2LI238 to monitor motions at different intersubunit interfaces. We expressed wild-type and mutant GABAARs in Xenopus oocytes. We measured rates of modification of the substituted cysteines in the absence and presence of different combinations of allosteric modulators that bind to different sites: the intravenous anesthetics pentobarbital (PB) and etomidate, the neurosteroid THDOC and the benzodiazepine flurazepam. When applied alone, flurazepam and THDOC induced distinct motions in the intersubunit interfaces, flurazepam increased rate of modification of only γI238C whereas THDOC only increased the rate of βL223C. When flurazepam and THDOC were co-applied, no change in rate of modification of γI238C was observed indicating that the presence of THDOC inhibited the ability of flurazepam to elicit structural rearrangements near γI238C. The data suggest structural mechanisms underlying the effects of combining drugs are different than mechanisms underlying their actions alone.

Anesthesia influences neuronal activity and drug effectiveness in neuropathic rats

In the study of neuropathic pain, the reduction of spinal neuronal activity by an analgesic drug can inform about site and mechanistic aspects of action. Animal experiments such as in vivo electrophysiological recordings from spinal neurons, however, largely require anesthesia. The impact of the anesthesia on the interpretation of the experimental result has been mostly disregarded. Here we report major differences in basal neuronal activity and the effectiveness of morphine and gabapentin under different anesthetics in the rat neuropathic pain model of chronic constriction injury (CCI). We compared data on basal neuronal activity and drug-induced modulation of spinal wide dynamic range neurons in CCI under isoflurane anesthesia with results under pentobarbital anesthesia. Morphine inhibited spinal neuronal activity in CCI operated rats under both anesthetic conditions. Gabapentin, however, only partially reduced spinal activity when the experiment was performed under pentobarbital anesthesia. A marked inhibitory effect of gabapentin can be revealed by isoflurane anesthesia. It could be expected that drug profiles of clinically active agents are similar across neuropathic pain models. Instead, our results suggest that the choice of the anesthetic influences electrophysiological results to a greater extent than the surgical protocol used to induce nerve injury in an animal model of neuropathic pain.

Glial response after inferior alveolar nerve injury

Inferior alveolar nerve (IAN) is the sensory branch of trigeminal nerve that innervates dental pulp and periodontal tissue and conveys somatosensory information to sensory nuclei in the brainstem. Peripheral nerve fibers of the IAN are damaged during dental surgeries such as endodontic procedure and tooth extraction. In some cases, taste deficits have been reported even at 6 month after the surgery suggesting alterations in gustatory function of central nervous system (CNS). Peripheral injury to sensory nerves causes glial responses at the primary nerve terminals of the ascending sensory pathways in the CNS. In the responses, microglia alters neural activity in the primary sensory nuclei. Because some of afferent fibers of IAN form synapses onto gustatory neurons in the rostral nucleus of the solitary tract (rNST), the microglia response may change in activity of the gustatory neurons upon IAN damage, which may lead to taste deficits. In this study, we investigated distribution of microglia in rNST after inferior alveolar nerve (IAN) transection as a first step to understand effects of IAN damage on the gustatory function. IAN in male Sprague-Dawley rats (eight weeks old) was transected at the left mandibular angle under pentobarbital anesthesia. Oneweek after the IAN transaction, a microglia-specific protein Iba1-immunoreactive (ir) cells were labeled with fluorescent immunohistochemistry in brainstem slices that include NST. Fluorescent images of the Iba1-ir cells were taken on a laser scanning confocal microscope. Glial responses were evaluated by counting pixels above threshold representing Iba1-immunoreactive products. Mean value was calculated for the pixel counts in defined six regions within NST. Comparison was made between IAN-transected and sham control groups using Mann-Whitney U test. Results with p < 0.05 was considered as significant. In NST, density of the pixels was significantly higher in the rostral-lateral region in the IAN-transected rats in comparisonwith the same region in sham rats. This result suggests taste deficits after dental surgery may be attributed to responses of rNST microglia to IAN damage.

Rabbit model of chest wall rigidity induced by fentanyl and the effects of apomorphine

A rabbit model for fentanyl-induced chest wall rigidity and the effect of apomorphine was evaluated. Eleven New Zealand adult rabbits were anesthetized and mechanically ventilated. An esophageal balloon catheter was used to estimate pleural pressure (Ppl). Chest wall compliance (Ccw) at baseline was calculated during pentobarbital anesthesia. A loading dose of 0.1mgkg−1 of fentanyl followed by infusion of 0.01mgkg−1min−1 was started in all animals, and Ccw reassessed. In the rabbits that developed decreased Ccw, apomorphine 0.4mgkg−1 followed by a 0.004mgkg−1min−1 was administered and Ccw was reassessed. Ccw at baseline and after fentanyl and fentanyl+apomorphine were compared with one-way ANOVA followed by Bonferroni–Holm test (P<0.05). In 5 rabbits, Ccw decreased significantly after fentanyl administration and apomorphine was able to restore Ccw to baseline values. Rabbits can be used as a model for fentanyl-induced chest wall rigidity. Results from this study support central dopaminergic pathways as being at least partially responsible for the opioid-induced chest wall rigidity.

Bacterial cellulose membranes used as artificial substitutes for dural defection in rabbits.

To improve the efficacy and safety of dural repair in neurosurgical procedures, a new dural material derived from bacterial cellulose (BC) was evaluated in a rabbit model with dural defects. We prepared artificial dura mater using bacterial cellulose which was incubated and fermented from Acetobacter xylinum. The dural defects of the rabbit model were repaired with BC membranes. All surgeries were performed under sodium pentobarbital anesthesia, and all efforts were made to minimize suffering. All animals were humanely euthanized by intravenous injection of phenobarbitone, at each time point, after the operation. Then, the histocompatibility and inflammatory effects of BC were examined by histological examination, real-time fluorescent quantitative polymerase chain reaction (PCR) and Western Blot. BC membranes evenly covered the surface of brain without adhesion. There were seldom inflammatory cells surrounding the membrane during the early postoperative period. The expression of inflammatory cytokines IL-1β, IL-6 and TNF-α as well as iNOS and COX-2 were lower in the BC group compared to the control group at 7, 14 and 21 days after implantation. BC can repair dural defects in rabbit and has a decreased inflammatory response compared to traditional materials. However, the long-term effects need to be validated in larger animals.

WPŁYW POLA MAGNETYCZNEGO O EKSTREMALNIE NISKIEJ CZĘSTOTLIWOŚCI NA ZAWARTOŚĆ GLUTATIONU W MIĘŚNIU POPRZECZNIE PRĄŻKOWANYM SZCZURA

Free radicals (FR) are atoms, molecules or their fragments. Their excess leads to the development of oxidizing stress, the cause of many neoplastic, neurodegenerative and inflammatory diseases, and aging of the organism. Industrial pollution, tobacco smoke, ionizing radiation, ultrasound and magnetic field are the major FR exogenous sources. The low frequency magnetic field is still more commonly applied in the physical therapy. The aim of the presented study was to evaluate the effect of extremely low frequency magnetic field used in the magnetotherapy on the level of total glutathione, oxidized and reduced, and the redox state of the skeletal muscle cells, depending on the duration of exposure to magnetic field. The male rats, weight of 280-300 g, were randomly devided into 3 experimental groups: controls (group I) and treatment groups exposed to extremely low frequency magnetic field (ELF-MF) (group II exposed to 40 Hz, 7 mT for 0.5 h/day for 14 days and group III exposed to 40 Hz, 7 mT for 1 h/day for 14 days). Control rats were kept in a separate room not exposed to extremely low frequency magnetic field. Immediately after the last exposure, part of muscles was taken under pentobarbital anesthesia. Total glutathione, oxidized and reduced, and the redox state in the muscle tissue of animals were determined after exposure to magnetic fields. Exposure to low magnetic field: 40 Hz, 7 mT for 30 min/day and 60 min/day for 2 weeks significantly increased the total glutathione levels in the skeletal muscle compared to the control group (p < 0.001). Exposure to magnetic fields used in the magnetic therapy plays an important role in the development of adaptive mechanisms responsible for maintaining the oxidation-reduction balance in the body and depends on exposure duration.

PPARγ and NAD(P)H oxidase system interaction in glycerol-induced acute renal failure: role of gp91phox subunit of NAD(P)H oxidase

Increased NAD(P)H oxidase-dependent free radical generation has been proposed to be a mechanism in glycerol-induced acute renal failure (ARF). Previously, we showed a PPARγ-mediated regulation of free radical generation in ARF. In this study, we examined NAD(P)H oxidase-dependent pathology in ARF and its connection with PPARγ using both Sprague–Dawley rats and gp91phox (+/−) mice. Male gp91phox (+/−) or wild type (+/+) mice were distributed into vehicle and ARF group (50% glycerol; 8 mL/kg bw; i.m.). Animals were placed in metabolic cages for 24 hr and were sacrificed under pentobarbital anesthesia. Urine, plasma and kidneys were processed for biochemical and molecular analysis. Glycerol doubled proteinuria in (+/+) mice (68 ± 4 mg/24 hr) but not in (+/−) mice (43 ± 9 mg/24 hr). This was associated with a markedly reduced creatinine excretion in (+/+) mice (Con: 0.6 ± 0.03 & ARF: 0.37 ± 0.02). Basal plasma and urinary NO was higher in (+/−) mice than the (+/+) type while plasma 8-isoprostane level was lower in (+/−) mice (WT: 165 ± 20; KO: 100 ± 15 pg/mL). Glycerol reduced UNOXV in both (+/+) and (+/−) mice although plasma NO was unchanged. Glycerol also doubled 8-isoprostane in (+/+) (363 ± 22 pg/mL) but not in (+/−) mice (152 ± 20 pg/mL) and this was associated with an increased NAD(P)H oxidase activity in the (+/+) mice. In ARF, PPARγ expression was reduced in (+/+) mice but increased in (+/−) mice. PPARγ activity was also reduced in (+/+) mice but was unchanged in (+/−) mice. We conclude that gp91phox contributes to NAD(P)H oxidase-mediated increased free radical generation in ARF and this may be via reduced PPARγ.

High-frequency micro-ultrasound: A novel method to assess external urethral sphincter function in rats following simulated birth injury

We evaluated external urethral sphincter (EUS) function using high-frequency micro-ultrasound (US) in rats that were either uninjured (Control, C) or underwent vaginal distension (VD) as a substitute for vaginal birth injury induced stress urinary incontinence (SUI). Thirteen female nulliparous Sprague-Dawley rats of 12 weeks were divided into two groups, either C (n = 6) or VD (n = 7). Vaginal balloon distension was performed under pentobarbital anesthesia for 4 hours. Five days after the injury, all animals underwent US assessment of the urethra during high-rate bladder filling and urine leakage/voiding. Urinary leakage, the presence, absence, and pattern of EUS bursting during the voiding phase were registered, and pre-determined parameters of intercontraction interval (ICI), length of contraction (LOC), and rate of contraction (ROC) were registered. Our ultrasound findings consistently showed the presence of rhythmic EUS bursting in all of the C rats (6/6), which were absent in all VD rats (0/7). The mean of ROC, ICI, and LOC in C group were 3.02 ± 0.12 contractions/sec, 471.43 ± 17.9 msec, and 103.41 ± 3.28 msec, respectively. Pre-determined parameters of LOC, ICI, and ROC during US provide objective and measurable data on EUS function. US showed the total disappearance of EUS bursting in the VD group as compared to the C group. These results indicate that ultrasound testing may become a valuable non-invasive tool in future translational studies to investigate SUI/urethral function in rat models.

Effects of Propofol on Electrocardiogram Measures in Mice

We investigated the anesthetic effects of propofol on the electrocardiogram (ECG) in mice. We also compared the effects of isoflurane (2%) inhalation anesthesia, intraperitoneal propofol (50 or 100 mg/kg), and pentobarbital (50 mg/kg) on ECG in mice. Isoflurane inhalation and pentobarbital anesthesia were both associated with an acceptable heart rate (HR) range (ca. 450 - 500 bpm). In contrast, high-dose propofol anesthesia significantly decreased the HR. Importantly, propofol anesthesia led to significantly reduced responses to propranolol, a β-blocker, suggesting that it affects sympathetic tonus and is not suitable for the evaluation of cardiovascular or sympathetic function. Propofol also reduced the response to atropine, indicative of suppression of mouse parasympathetic nerve activity. Our data suggest that propofol anesthesia should not be the first choice for cardiovascular analysis in mice.

Allosteric Modulation of GABA-A Receptors by Different Drugs

Understanding how drugs allosterically modulate GABA-A receptor (GABAAR) channel function remains a challenge. Anesthetic drugs like etomidate, propofol and pentobarbital bind at transmembrane domain (TMD) inter-subunit interfaces at different locations. Benzodiazepines bind at the αγ interface in the extracellular domain (ECD) and neurosteroids are believed to bind within the α-subunit TMD helix bundle. A common feature of these drugs is that they potentiate GABA-induced currents. Here, we examined whether structural mechanisms underlying their functional effects are distinct. We monitored motions induced individually by these drugs at each inter-subunit TMD interface and also tested whether modulation caused by pairs of drugs binding to distinct sites are additive or super-additive. We individually introduced a cysteine in the M1 helices of each subunit at α1I227, β2L223 and γ2LI238 to probe the different inter-subunit interfaces. We expressed wild-type and mutant α1β2γ2L GABAARs in Xenopus oocytes and measured rates of modification of the substituted cysteines in the absence and presence of GABA and different allosteric modulators: the anesthetics pentobarbital (PB) and etomidate, the neurosteroid THDOC and the benzodiazepine flurazepam. GABA activation significantly increased MTSEA modification of αI227C, βL223C and γI238C. PB activation increased modification of αI227C and γI238C but not βL223C. Modulating concentrations of PB or etomidate had no effects. THDOC significantly increased the rate of modification of βL223C whereas flurazepam increased γI238C modification. We found that potentiation of EC10 GABA currents by combining modulating concentrations of THDOC and flurazepam was the sum of the potentiation produced by the two drugs individually. Combining PB and THDOC produced potentiation more than the sum of the potentiation produced by the two drugs individually. Our data suggests that drugs binding to different sites act via distinct mechanisms. Further analysis is underway to determine if these mechanisms are independent or coupled.

Acute Experimental Diabetes and Aortic Depressor Nerve Ultrastructural Morphometry: Effects of Insulin Treatment

Previous results from our laboratory showed myelinated fiber alterations in the aortic depressor nerve (ADN) from rats rendered diabetic for 15 days (short term). The ultrastructure and the acute effect of insulin treatment, particularly in the unmyelinated fibres of this nerve, were not yet investigated in this experimental model, being the aim of this work. Wistar rats received a single intravenous injection of streptozotocin (STZ – 40 mg/Kg) 15 days (N=7) before the experiments. Control animals (N=7) received vehicle (citrate buffer) and treated animals (n=6) received a subcutaneous injection of insulin (10 IU/Kg) on a daily basis beginning 3 days after the STZ injection. Under pentobarbital anaesthesia the ADNs were isolated and had their spontaneous activity recorded. Afterwards, proximal and distal segments of the nerves were prepared for transmission electron microscopy studies. Morphometry of the myelinated and unmyelinated fibres was carried out with the aid of computer software. Nerves from diabetic animals showed some unmyelinated fiber enlargement with signs of swelling and degeneration, and the Schwann cells mitochondria presented enlargement and clustering formation. On treated animals, an important thickening of the Schwann cells’ basement membrane was present and some myelinated fibers showed thin myelin sheaths. The endoneural blood vessels ultrastrucutre was preserved in all nerves from the three experimental groups. Myelinated axon area and diameter was significantly larger on insulin treated animals, compared to both, controls and acute diabetic groups, on both segments. No other differences were observed between groups for the myelinated or unmyelinated fibers morphometric parameters. Investigation of experimental models of diabetes in early or acute stage of the disease provide relevant information on the physiopathological mechanisms involved in the alterations present in patients with chronic diabetes and its complications. We suggest that insulin treatment alone might have a role on the morphological alterations present in diabetic neuropathy.

Type 1 metabotropic glutamate receptors (m G lu1) trigger the gating of G lu D 2 delta glutamate receptors

The orphan GluD2 receptor belongs to the ionotropic glutamate receptor family but does not bind glutamate. Ligand-gated GluD2 currents have never been evidenced, and whether GluD2 operates as an ion channel has been a long-standing question. Here, we show that GluD2 gating is triggered by type 1 metabotropic glutamate receptors, both in a heterologous expression system and in Purkinje cells. Thus, GluD2 is not only an adhesion molecule at synapses but also works as a channel. This gating mechanism reveals new properties of glutamate receptors that emerge from their interaction and opens unexpected perspectives regarding synaptic transmission and plasticity.

Point Mutation in Syntaxin-1A Causes Abnormal Vesicle Recycling, Behaviors, and Short Term Plasticity

Syntaxin-1A is a t-SNARE that is involved in vesicle docking and vesicle fusion; it is important in presynaptic exocytosis in neurons because it interacts with many regulatory proteins. Previously, we found the following: 1) that autophosphorylated Ca(2+)/calmodulin-dependent protein kinase II (CaMKII), an important modulator of neural plasticity, interacts with syntaxin-1A to regulate exocytosis, and 2) that a syntaxin missense mutation (R151G) attenuated this interaction. To determine more precisely the physiological importance of this interaction between CaMKII and syntaxin, we generated mice with a knock-in (KI) syntaxin-1A (R151G) mutation. Complexin is a molecular clamp involved in exocytosis, and in the KI mice, recruitment of complexin to the SNARE complex was reduced because of an abnormal CaMKII/syntaxin interaction. Nevertheless, SNARE complex formation was not inhibited, and consequently, basal neurotransmission was normal. However, the KI mice did exhibit more enhanced presynaptic plasticity than wild-type littermates; this enhanced plasticity could be associated with synaptic response than did wild-type littermates; this pronounced response included several behavioral abnormalities. Notably, the R151G phenotypes were generally similar to previously reported CaMKII mutant phenotypes. Additionally, synaptic recycling in these KI mice was delayed, and the density of synaptic vesicles was reduced. Taken together, our results indicated that this single point mutation in syntaxin-1A causes abnormal regulation of neuronal plasticity and vesicle recycling and that the affected syntaxin-1A/CaMKII interaction is essential for normal brain and synaptic functions in vivo.

The Impact of Four Different Classes of Anesthetics on the Mechanisms of Blood Pressure Regulation in Normotensive and Spontaneously Hypertensive Rats

Most anesthetics induce characteristic hemodynamic changes leading to blood pressure (BP) reduction but the role of renin-angiotensin system (RAS), sympathetic nervous system (SNS) and nitric oxide (NO) synthesis in this BP reduction is unknown. We therefore studied the influence of four widely used anesthetics - pentobarbital (P), isoflurane (ISO), ketamine-xylazine (KX) and chloralose-urethane (CU) - on the participation of these vasoactive systems in BP maintenance. BP effects elicited by the acute sequential blockade of RAS (captopril), SNS (pentolinium) and NO synthase (L-NAME) were compared in conscious and anesthetized Wistar or spontaneously hypertensive rats (SHR). Except for pentobarbital all studied anesthetics evidenced by diminished BP responses to pentolinium. The absolute pentolinium-induced BP changes were always greater in SHR than Wistar rats. KX anesthesia eliminated BP response to pentolinium and considerably enhanced BP response to NO synthase inhibition in SHR. In both rat strains the anesthesia with ISO or CU augmented BP response to captopril, decreased BP response to pentolinium and attenuated BP response to NO synthase inhibition. In conclusion, pentobarbital anesthesia had a modest influence on BP level and its maintenance by the above vasoactive systems. Isoflurane and chloralose-urethane anesthesia may be used in cardiovascular experiments if substantial BP decrease due to altered contribution of RAS, SNS and NO to BP regulation does not interfere with the respective research aim. Major BP reduction (namely in SHR) due to a complete SNS absence is a major drawback of ketamine-xylazine anesthesia.

P.1.j.022 A dopamine D1 agonist improved ketamineinduced spatial working memory dysfunction in common marmosets

Using the RNA arbitrarily-primed PCR and the competitive RT-PCR, we have isolated the neocortical transcripts that are upregulated and unchanged in the adult and infant rats, respectively, after a systemic injection of an N-methyl-d-aspartate (NMDA) receptor antagonist phencyclidine (PCP), and found them identical to the synapse-associated protein-97 (SAP97) gene mRNAs. The upregulation of the SAP97 transcripts in the adult neocortex after the acute PCP injection was mimicked by another NMDA antagonist, dizocilpine, but not by the indirect dopamine agonists, methamphetamine and cocaine, a selective D1 receptor antagonist SCH23390, a D2 receptor-preferring antagonist haloperidol and a GABAergic anesthetic pentobarbital. Moreover, the pretreatment with a typical antipsychotic haloperidol failed to antagonize the increased neocortical SAP97 gene expression by PCP. These findings suggest that SAP97 might be involved in the molecular basis of the development-dependent onset of the non-dopaminergic symptoms seen in schizophrenia and the schizophrenia-like psychosis induced by NMDA receptor blocking.

Atrial natriuretic peptide reduces hepatic ischemia–reperfusion injury in rabbits

Atrial natriuretic peptide (ANP) has been known to be protective against hepatic ischemia/reperfusion injury. The purpose of this study was to verify the hypothesis that ANP conserves microvascular circulation and reduces ischemia-reperfusion injury in the in vivo rabbit model. With IRB approval, 30 male Japanese white rabbits under pentobarbital anesthesia were studied. These animals were randomly assigned to the following three groups (n = 10 each): control, ANP, and sham group. Animals in the ANP group received continuous infusion of ANP at 0.1 μg/kg/min throughout the study period. Animals in control and ANP groups underwent 90 min of partial hepatic ischemia by clamping the right hepatic artery and portal vein. Descending aortic blood flow (AoF) was monitored with a transit-time ultrasound flowmeter. Hepatic tissue microvascular blood flow (HTBF) at both right (ischemic) and left (nonischemic) lobe was intermittently evaluated with the hydrogen clearance method. After 180 min of reperfusion, hepatic injury was determined with serum AST and ALT. Galactose clearance of reperfused right lobe was also measured as an indicator of hepatic metabolic function. Histopathological change and the number of apoptotic hepatocytes were also evaluated. Systemic hemodynamic data including mean arterial pressure, heart rate, and AoF did not differ among the three groups during the study period. ANP attenuated ischemia-induced right HTBF decrease. ANP also suppressed histopathological degeneration, apoptosis, and decline in galactose clearance after reperfusion. ANP attenuated hepatic microvascular dysfunction and hepatocyte injury after reperfusion without significant hemodynamic change.