Receptor Function In Rats Research Articles

Apelin-13 Protects Against Lipopolysaccharide-Induced Neuroinflammation and Cognitive Decline by Restoring Glucocorticoid Receptor Function in Rats

Apelin-13 Protects Against Lipopolysaccharide-Induced Neuroinflammation and Cognitive Decline by Restoring Glucocorticoid Receptor Function in Rats

Interactive effects of morphine and nicotine on memory function depend on the central amygdala cannabinoid CB1 receptor function in rats

The present study investigated the possible involvement of the central amygdala (CeA) cannabinoid receptors type-1 (CB1Rs) in the interactive effects of morphine and nicotine on memory formation in a passive avoidance learning task. Our results showed that systemic administration of morphine (3 and 6mg/kg, s.c.) immediately after training phase impaired memory consolidation and induced amnesia. Administration of nicotine (0.3 and 0.6mg/kg, s.c.) before testing phase significantly restored morphine-induced amnesia, suggesting a cross state-dependent learning between morphine and nicotine. The results showed that while the administration of the lower dose of nicotine (0.1mg/kg, s.c.) per se did not induce a significant effect on morphine-induced amnesia, intra-CeA injection of arachidonylcyclopropylamide (ACPA), a cannabinoid CB1 receptor agonist (3 and 4ng/rat), significantly potentiated the nicotine response. Furthermore, the blockade of the CeA cannabinoid CB1 receptors by the injection of AM251 (0.75 and 1ng/rat) reversed the potentiative effect of nicotine (0.6mg/kg, s.c.) on morphine-induced amnesia. It should be considered that bilateral injection of the same doses of ACPA or AM251 (0.5–1ng/rat) into the CeA by itself had no effect on morphine response in a passive avoidance learning task. Confirmed by the cubic interpolation planes, the dose-response data revealed a cross-state-dependent learning between morphine and nicotine which may be mediated by the CeA endocannabinoid system via CB1 receptors.

Protein disulfide isomerase regulates renal AT1 receptor function and blood pressure in rats.

The role and mechanism of renal protein disulfide isomerase (PDI) in blood pressure regulation has not been tested before. Here, we test this possibility in Sprague-Dawley rats. Rats were treated with PDI inhibitor bacitracin (100 mg·kg-1 ip·day-1 for 14 days), and then blood pressure and renal angiotensin II type 1 (AT1) receptor function were determined in anesthetized rats. Renal AT1 receptor function was determined as the ability of candesartan (an AT1 receptor blocker) to increase diuresis and natriuresis. A second set of vehicle- and bacitracin-treated rats was used to determine biochemical parameters. Systolic blood pressure as well as diastolic blood pressure increased in bacitracin-treated compared with vehicle-treated rats. Compared with vehicle, bacitracin-treated rats showed increased diuresis and natriuresis in response to candesartan (10-µg iv bolus dose) suggesting higher AT1 receptor function in these rats. These were associated with higher renin activities in the plasma and renal tissues. Furthermore, urinary 8-isoprostane and kidney injury molecule-1 levels were higher and urinary antioxidant capacity was lower in bacitracin-treated rats. Renal protein carbonyl and nitrotyrosine levels also were higher in bacitracin- compared with vehicle-treated rats, suggesting oxidative stress burden in bacitracin-treated rats. Moreover, PDI activity decreased and its protein levels increased in renal tissues of bacitracin-treated rats. Also, nuclear levels of Nrf2 transcription factor, which regulates redox homeostasis, were decreased in bacitracin-treated rats. Furthermore, tissue levels of Keap1, an Nrf2 inhibitory molecule, and tyrosine 216-phosphorylated GSK3β protein, an Nrf2 nuclear export protein, were increased in bacitracin-treated rats. These results suggest that renal PDI by regulating Keap1-Nrf2 pathway acts as an antioxidant, maintaining redox balance, renal AT1 receptor function, and blood pressure in rats.

Downregulation of nicotinic and muscarinic receptor function in rats after subchronic exposure to diazinon.

Diazinon (DZN) is an organophosphate insecticide which exerts its effect through the inhibition of acetylcholinesterase enzyme (AChE). In this work, we studied the development of tolerance to subchronic p.o. administration of DZN in rats, under both in vivo and in vitro conditions. A group of 20 rats (2 groups, n=10) was administered p.o. the 1/10 of established LD50 DZN (namely 55.87mg/kgbw) for 28days. On the 14th and 28th day of study with isolated diaphragm and ileum, we examined the downregulation of nicotinic and muscarinic receptor function through Electrical Field Stimulation (EFS). Maximum contractility of the diaphragm was recorded on the 14th day of the study (25% higher compared to the non-treated rats), while on the 28th day the contractions almost did not differ from the values found in non-treated rats. EFS of isolated ileum on the 14th day of study caused significantly higher contractions compared to the non-treated rats, but after 28days, ileum contractions decreased approximately to the level of contractions in non-treated rats. On the 14th study day, we also recorded increased amplitude of spontaneous ileum contractions, compared to non-treated rats. The application of increasing ACh concentrations caused dose-dependent ileum contractions, without statistically significant differences of median effective concentration (EC50) values in non-treated and treated rats. Tolerance to subchronic DZN administration develops due to various adaptation mechanisms, including the most important one-downregulation of nicotinic and muscarinic receptor function.

Isoflurane (ISO) Inhibits Bronchopulmonary C‐fiber‐mediated Apneic Response to phenylbiguanide (PBG) by Depressing 5‐HT3 Receptor Function in Rats

Our previous study has shown that isoflurane (ISO), a commonly used volatile anesthetic, has an excitatory effect on bronchopulmonary C‐fibers (PCFs) (Zhang, et al., EB 2011, A377). Because right atrial bolus injection of PBG has been extensively used to selectively stimulate PCFs by action on local 5‐HT3 receptor, and thereby evoking an apnea, we asked whether inhalation of ISO would facilitate the PCF 5‐HT3 receptor‐mediated apneic response, and if so, how. Our experiments were performed in three groups of rats. We recorded the ventilatory response and pulmonary C neural response to right atrial bolus injection of PBG (25 μg/kg) before and during inhalation of 5% ISO. To this end, the ventilatory response was recorded in anesthetized and spontaneously breathing rats (Group I), while pulmonary C neurons were electrophysiologically isolated and extracellularly recorded in the nodose ganglion of anesthetized and paralyzed rats (Group II). Using perforated patch clamp technique in vitro, we further tested the effect of ISO (1 mM) on the PBG‐induced inward current of pulmonary C neurons labeled by previously instilling 1,1′‐dioctadecyl‐3,3,3′,3′‐tetramethylindocarbocyanine perchlorate (DiI) into the airways and lungs (Group III). Our results showed that inhalation of ISO markedly shortened the PBG‐produced apnea and attenuated the PBG‐elicited excitation of pulmonary C neurons. Moreover, ISO perfusion depressed the PBG‐induced inward current of pulmonary C neurons. These data suggest that ISO can inhibit PCF 5‐HT3 channel function to attenuate PCF excitatory response to PBG, likely contributing to shortening the PBG‐induced apnea by ISO in rats. (Supported by HL 107462 and ALA RG‐191095‐N)

Loss of renal medullary endothelin B receptor function during salt deprivation is regulated by angiotensin II

We have recently demonstrated that chronic infusion of exogenous ANG II, which induces blood pressure elevation, attenuates renal medullary endothelin B (ET(B)) receptor function in rats. Moreover, this was associated with a reduction of ET(B) receptor expression in the renal inner medulla. The aim of this present work was to investigate the effect of a physiological increase in endogenous ANG II (low-salt diet) on the renal ET system, including ET(B) receptor function. We hypothesized that endogenous ANG II reduces renal medullary ET(B) receptor function during low-salt intake. Rats were placed on a low-salt diet (0.01-0.02% NaCl) for 2 wk to allow an increase in endogenous ANG II. In rats on normal-salt chow, the stimulation of renal medullary ET(B) receptor by ET(B) receptor agonist sarafotoxin 6c (S6c) causes an increase in water (3.6 ± 0.4 from baseline vs. 10.5 ± 1.3 μl/min following S6c infusion; P < 0.05) and sodium excretion (0.38 ± 0.06 vs. 1.23 ± 0.17 μmol/min; P < 0.05). The low-salt diet reduced the ET(B)-dependent diuresis (4.5 ± 0.5 vs. 6.1 ± 0.9 μl/min) and natriuresis (0.40 ± 0.11 vs. 0.46 ± 0.12 μmol/min) in response to acute intramedullary infusion of S6c. Chronic treatment with candesartan restored renal medullary ET(B) receptor function; urine flow was 7.1 ± 0.9 vs. 15.9 ± 1.7 μl/min (P < 0.05), and sodium excretion was 0.4 ± 0.1 vs. 1.1 ± 0.1 μmol/min (P < 0.05) before and after intramedullary S6c infusion, respectively. Receptor binding assays determined that the sodium-depleted diet resulted in a similar level of ET(B) receptor binding in renal inner medulla compared with rats on a normal-salt diet. Candesartan reduced renal inner medullary ET(B) receptor binding (1,414 ± 95 vs. 862 ± 50 fmol/mg; P < 0.05). We conclude that endogenous ANG II attenuates renal medullary ET(B) receptor function to conserve sodium during salt deprivation independently of receptor expression.

Testosterone improves cardiac function and alters angiotensin II receptors in isoproterenol-induced heart failure

The renin-angiotensin-aldosterone system is known to play an important role in the pathophysiology and development of heart failure. Several studies have reported the benefits of testosterone in heart failure. However, the mechanisms of testosterone-induced effects on heart failure require further study. To determine the effects of castration and testosterone administration on cardiac function and angiotensin II receptor function in rats with isoproterenol-induced heart failure. Wistar rats were divided randomly into control and heart failure groups. The heart failure groups were further divided into the following groups: castration; castration+testosterone replacement; and sham castration. Echocardiography and haemodynamic measurements were used to evaluate cardiac function. Cardiocyte apoptosis and fibrosis were determined using terminal deoxyribonucleotide transferase-mediated dUTP nick-end labelling (TUNEL) staining and Masson's Trichrome staining, respectively. Angiotensin II receptor (AT1 and AT2) messenger ribonucleic acid (mRNA) expression levels were assayed using real-time reverse transcriptase-polymerase chain reactions, while Western immunoblotting was used to estimate Bcl-2 protein expression levels. Castration significantly increased cardiomyocyte apoptosis and fibrosis that was normally induced by isoproterenol (P<0.05). AT2 receptor mRNA expression in the castration group was increased and Bcl-2 protein expression was decreased compared with the castration+testosterone replacement group (P<0.05). These data suggest that androgen therapy could play an important role in pathophysiological changes in heart failure and have beneficial effects for its treatment.

Urethane, but not pentobarbitone, attenuates presynaptic receptor function in rats: a contribution to the choice of anaesthetic

We examined whether cannabinoid CB(1) and histamine H(3) receptors resemble alpha(2)-adrenoceptors in that their presynaptically mediated cardiovascular effects are less marked in urethane- than in pentobarbitone-anaesthetized pithed rats. Effects of the cannabinoid agonist CP-55,940 and the H(3) receptor agonist imetit on electrically induced tachycardic and vasopressor responses, respectively, was compared in pithed rats anaesthetized with urethane or pentobarbitone. The affinity of urethane for the three receptors was measured by radioligand binding studies in rat brain cortex membranes and its potency assessed in superfused mouse tissues preincubated with (3)H-noradrenaline. The neurogenic tachycardic response was less markedly inhibited by CP-55,940 in urethane- than in pentobarbitone-anaesthetized pithed rats. Imetit inhibited the neurogenic vasopressor response after pentobarbitone but not after urethane. The catecholamine-induced tachycardic and vasopressor response did not differ between rats anaesthetized with either compound. Urethane 10 mM (plasma concentration reached under anaesthesia) did not affect binding to CB(1) or H(3) receptors and alpha(2) adrenoceptors, nor did it alter the inhibitory effect of agonists at the three receptors on electrically evoked (3)H-noradrenaline release. Urethane, but not pentobarbitone, abolished the H(3) receptor-mediated vascular response in pithed rats and attenuated the CB(1) receptor-mediated cardiac response much more than pentobarbitone. The weaker effects of CB(1), H(3) and alpha(2) receptor agonists cannot be explained by antagonism by urethane at the three receptors in vitro. Pentobarbitone, but not urethane, is suitable as an anaesthetic for investigations of inhibitory presynaptic receptor function in pithed and anaesthetized rats.

MicroPET imaging of 5-HT1A receptors in rat brain: a test–retest [18F]MPPF study

Earlier studies have shown that positron emission tomography (PET) imaging with the radioligand [(18)F]MPPF allows for measuring the binding potential of serotonin 5-hydroxytryptamine(1A) (5-HT(1A)) receptors in different regions of animal and human brain, including that of 5-HT(1A) autoreceptors in the raphe nuclei. In the present study, we sought to determine if such data could be obtained in rat, with a microPET (R4, Concorde Microsystems). Scans from isoflurane-anaesthetised rats (n = 18, including six test-retest) were co-registered with magnetic resonance imaging data, and binding potential, blood to plasma ratio and radiotracer efflux were estimated according to a simplified reference tissue model. Values of binding potential for hippocampus (1.2), entorhinal cortex (1.1), septum (1.1), medial prefrontal cortex (1.0), amygdala (0.8), raphe nuclei (0.6), paraventricular hypothalamic nucleus (0.5) and raphe obscurus (0.5) were comparable to those previously measured with PET in cats, non-human primates or humans. Test-retest variability was in the order of 10% in the larger brain regions (hippocampus, medial prefrontal and entorhinal cortex) and less than 20% in small nuclei such as the septum and the paraventricular hypothalamic, basolateral amygdaloid and raphe nuclei. MicroPET brain imaging of 5-HT(1A) receptors with [(18)F]MPPF thus represents a promising avenue for investigating 5-HT(1A) receptor function in rat.

Gene transfer of neuronal nitric oxide synthase to the paraventricular nucleus improves enhanced NMDA NR1 receptor function in rats with chronic heart failure

Our previous studies have shown that the decreased nitric oxide (NO) and increased glutamatergic mechanisms’ effects on sympathetic regulation within the paraventricular nucleus (PVN) may contribute to the elevated sympathoexcitation during chronic heart failure (CHF). In the present study, we investigated the effects of neuronal NO synthase (nNOS) gene transfer on NMDA NR1 receptor function in the rats with coronary ligation model of CHF. Adenovirus vectors encoding either nNOS (AdnNOS) or β-galactosidase (AdβGal, as control) were transfected into the PVN in vivo. Three days after application of AdnNOS, the nNOS mRNA expression and protein level were significantly increased within the PVN in rats with CHF (compared to AdβGal-CHF group, P<0.05). The renal sympathetic nerve activity (RSNA), blood pressure (BP) and heart rate (HR) responses to microinjection of NMDA into the PVN was significantly potentiated (RSNA: 42±2%, P<0.05) in the rats with CHF compared with sham rats. AdnNOS significantly decreased the enhanced RSNA, BP and HR responses to NMDA in the rats with CHF (RSNA: 35±4%, compared to AdβGal-CHF group, P<0.05). These results indicate that the effects of endogenous nNOS on the glutamatergic mechanism within the PVN may play an important role in the altered balance and tone of sympathetic outflow in the CHF condition.

Amphetamine-induced locomotion, behavioral sensitization to amphetamine, and striatal D 2 receptor function in rats with high or low spontaneous exploratory activity: Differences in the role of locus coeruleus

Individual differences in novelty-related behavior are associated with sensitivity to various neurochemical manipulations. In the present study the amphetamine-induced locomotor activity and behavioral sensitization to amphetamine (0.5 mg/kg) was investigated in rats with high or low spontaneous exploratory activity (HE- and LE-rats, respectively) after partial denervation of the locus coeruleus (LC) projections with a low dose of the selective neurotoxin DSP-4 ( N-(2-chloroethyl)- N-ethyl-2-bromobenzylamine; 10 mg/kg). DSP-4 produced a partial depletion (about 30%) of noradrenaline in the frontal cortex of both HE- and LE-rats; additionally the levels of metabolites of dopamine and 5-HT were reduced in the frontal cortex and nucleus accumbens of the LE-rats. Amphetamine-stimulated locomotor activity was attenuated by the DSP-4 pretreatment only in the HE-rats and this effect persisted over repeated testing. Behavioral sensitization to repeated amphetamine was evident only in the LE-rats with intact LC projections. Repeated amphetamine treatment reduced D 2 receptor mediated stimulation of [ 35S]GTPγS-binding and dopamine-dependent change in GDP-binding affinity in the striatum, but only in HE-rats. The absence of amphetamine sensitization in HE-rats could thus be related to the downregulation by amphetamine of the G protein stimulation through D 2 receptors. Conclusively, acute and sensitized effects of amphetamine depend on the integrity of LC projections but are differently regulated in animals with high or low trait of exploratory activity. These findings have implications to the neurobiology of depression, drug addiction, and attention deficit hyperactivity disorder.

Effects of low dose N-(2-chloroethyl)- N-ethyl-2-bromobenzylamine administration on exploratory and amphetamine-induced behavior and dopamine D 2 receptor function in rats with high or low exploratory activity

Individual differences in behavioral traits are associated with sensitivity to various neurochemical and psychopharmacological manipulations. In this study exploratory and amphetamine-induced behavior in rats with persistently high or low exploratory activity (HE and LE, respectively) was examined before and after a partial denervation of the locus coeruleus (LC) projections with the selective neurotoxin DSP-4 ( N-(2-chloroethyl)- N-ethyl-2-bromobenzylamine; 10 mg/kg). Partial LC denervation prevented the increase in exploratory activity over repeated test sessions in the LE animals, but had no effect in HE-rats. Amphetamine- (0.5 mg/kg) induced locomotor activity was attenuated by DSP-4 pretreatment only in HE-rats. These results suggest differential involvement of LC noradrenergic transmission in novelty- and amphetamine-induced behavior in animals with persistent differences in novelty-related behavior. In addition to partial noradrenaline depletion in the frontal cortex and hippocampus, which occurred in both HE- and LE-rats, DSP-4 treatment also decreased the content of dopamine and its metabolites in the nucleus accumbens, and the metabolite levels in striatum, but only in the LE-animals. 5-HIAA levels were also reduced in the nucleus accumbens and striatum in LE-rats by the neurotoxin. D 2 receptor function, as determined by dopamine-stimulated [ 35S]GTPγS binding, was increased by DSP-4 treatment in the striatum of LE-rats, but reduced in HE-rats. No effect of partial LC denervation was found on dopamine-stimulated [ 35S]GTPγS binding in the nucleus accumbens. Together these findings suggest that LC noradrenergic neurotransmission is differently involved in dopaminergic mechanisms which mediate novelty-related vs amphetamine-induced behavior.

Inhibitory effects of spinal baclofen on spinal dorsal horn neurones in inflamed and neuropathic rats in vivo

γ-Aminobutyric acid (GABA) is a major inhibitory neurotransmitter, which modulates afferent transmission of nociceptive information at different levels of the central nervous system. Plasticity of spinal GABAergic systems may contribute to aberrant nociceptive responses associated with inflammatory and neuropathic pain states. Here potential changes in spinal GABA B receptor function in rats with peripheral inflammation and nerve injury, compared to control were investigated. Extracellular recordings of electrically evoked responses of spinal dorsal horn neurones were made in halothane anaesthetised rats. Effects of spinal administration of the GABA B receptor agonist baclofen (0.1–10 μg/50 μl) on evoked responses of spinal neurones in control, hindpaw carrageenan inflamed, spinal nerve ligated and sham-operated rats were studied. In all groups of rats, spinal baclofen significantly reduced Aβ-, Aδ- and C-fibre evoked responses of spinal dorsal horn neurones in a dose related manner. Spinal pre-administration of the GABA B receptor antagonist, CGP-35348 (30 μg/50 μl) significantly blocked the inhibitory effects of baclofen on evoked neuronal responses in control rats. Estimated ED 50 values for each fibre type within experimental groups were calculated, a significant ( P<0.05) difference between the values for Aβ-fibre-evoked and C-fibre mediated post-discharge responses of spinal dorsal horn neurones in spinal nerve ligated rats is reported. This finding may reflect decreased sensitivity of Aβ-fibre-evoked responses to baclofen, as well as an increased sensitivity of post-discharge responses to baclofen in spinal nerve ligated rats. Overall, we report that GABA B-receptor control of A- and C-fibre evoked responses of spinal neurones is not profoundly altered in models of inflammatory and neuropathic pain.

Ovariectomy-Induced Increases in Hypothalamic Serotonin-1A Receptor Function in Rats Are Prevented by Estradiol

The present study investigated the effects of long-term estradiol withdrawal (ovariectomy) on hypothalamic serotonin-1A (5-HT_1A) receptor signaling. Changes in neuroendocrine responses to the 5-HT_1A agonist 8-OH-DPAT and levels of G_z protein in the hypothalamus were used to examine 5-HT_1A receptor signaling. Five days following ovariectomy, rats received daily injections of either 2 µg of β-estradiol 3-benzoate or vehicle (subcutaneously) for 2, 4 or 14 days. Twenty-four hours after the last injection, and 15 min prior to sacrifice, rats were injected with (±)8-OH-DPAT (50 µg/kg, s.c.) or saline. Estradiol treatment did not alter basal corticotropin (ACTH) or oxytocin levels. Injection of (±)8-OH-DPAT produced significant increases in plasma ACTH and oxytocin levels. In the vehicle-treated rats, hormone responses to 8-OH-DPAT were enhanced in rats that received injections for 14 days compared with rats that received injections for either 2 or 4 days. Estradiol treatment for 4 or 14 days blunted this enhanced ACTH response to 8-OH-DPAT, whereas the oxytocin response to 8-OH-DPAT was only blunted after 14 daily injections of β-estradiol 3-benzoate. The treatment with β-estradiol 3-benzoate (2 µg/rat) did not reduce membrane-associated G_z protein levels in the paraventricular nucleus of the hypothalamus. Hence, the inhibitory influence of a low dose of β-estradiol 3-benzoate on 5-HT_1A receptor signaling in the hypothalamus is not accompanied by a change in the levels of G_z protein in the paraventricular hypothalamic nucleus. Results from the present study indicate a supersensitivity of 5-HT_1A receptors after withdrawal of estradiol and suggest that estradiol suppresses 5-HT_1A receptor signaling.

Modulation of serotonin2a receptor function in rats after repeated treatment with dexamethasone and L-type calcium channel antagonist nimodipine

1. It has been conceivable that the hypothalamic-pituitary-adrenal (HPA) axis hyperactivity plays an important role in the pathophysiology of depression. In the present study, we have investigated the effect of repeated treatment with dexamethasone on serotonin (5-HT) 1A, 5-HT2A and α1-adrenergic receptors in the rat frontal cortex. Moreover, several studies have suggested the effectiveness of L-type calcium channel antagonist nimodipine for the treatment of depression. We also investigated the effect of repeated treatment with nimodipine on 5-HT2A receptor in rats with repeated dexamethasone treatment. 2. Repeated treatment with dexamethasone (1 mg/kg/day for 14 days) increased the density of 5-HT2A receptor, but not 5-HT1A and α1-adrenergic receptors in the rat frontal cortex. 3. The density of 5-HT2A receptor in the rat frontal cortex was significantly increased 1 day after repeated treatment with dexamethasone, but was not increased 7 or 14 days after repeated treatment. Wet dog shakes (WDS) induced by (±)-1-(4-iodo-2,5-dimethoxyphenyl)-2-aminopropane hydrochloride (DOI), a 5-HT2A receptor agonist, in rats were significantly enhanced 1, 7 and 14 days after repeated treatment with dexamethasone, although the frequency of WDS gradually decreased after repeated treatment. 4. Repeated treatment with nimodipine (5 mg/kg/day for 14 days) attenuated DOI-induced WDS enhanced by repeated treatment with dexamethasone (1 mg/kg/day for 14 days), however, it did not change the density of 5-HT2A receptor. Repeated treatment with dexamethasone decreased locomotor activity and body weight, but repeated treatment with nimodipine did not recover these parameters. 5. The results of the present study suggest that repeated treatment with dexamethasone may selectively increase the 5-HT2A receptor in the rat frontal cortex and affect 5-HT2A receptor-mediated signal transduction. In addition, the intracellular calcium homeostasis by blocking calcium influx through L-type calcium channel may play an important role in the regulation of the 5-HT2A receptor function by dexamethasone.

Antisense inhibition of delta-opioid receptor gene function in vivo by peptide nucleic acids.

Peptide nucleic acids (PNA) are synthetic analogs of DNA that hybridize to complementary oligonucleotide sequences with exceptional affinity and target specificity. The stability of PNA in biological fluids together with the unique hybridization characteristics of these structures suggests that PNA may have considerable potential as antisense agents for experimental use in vivo. To test this hypothesis, we attempted to modulate supraspinal delta-opioid receptor function in rats using PNA sequences designed to be complementary to a region of the rat delta-opioid receptor. Repeated i.c.v. administration of PNA over a period of 5 days significantly inhibited the antinociceptive response and locomotor response to selective delta-opioid receptor agonists. PNA attenuated delta-opioid receptor function in a sequence-specific, target-specific, and reversible manner characteristic of the functional inhibition caused by an antisense mechanism. There were no apparent toxicities arising from the PNA treatment based on the behavior of the animals and inspection of the treated tissues. Saturation binding studies on brain homogenates did not reveal any significant difference in receptor B(max) between treatment groups. However, [(35)S]guanosine-5'-O-(3-thio)triphosphate binding assays demonstrated a significant decrease in agonist efficacy in homogenates prepared from antisense-treated rats. Taken together, these results demonstrate that peptide nucleic acids are effective antisense agents in vivo and suggest that PNA may be a useful alternative to phosphodiester or phosphorothioate oligonucleotides, or variants thereof, for determination of gene function in vivo.

Measurement of GABAA receptor function in rat cultured cerebellar granule cells by the Cytosensor microphysiometer.

1. gamma-Aminobutyric acid (GABA), acting via the GABAA receptor, increased the extracellular acidification rate of rat primary cultured cerebellar granule cells, measured by the Cytosensor microphysiometer. 2. The optimal conditions for the measurement of GABAA receptor function in cerebellar granule cells by microphysiometry were: cells seeded at 9-12 x 10(5) cells/transwell cup and maintained in vitro for 8 days, GABA stimulation performed at 25 degrees C, with a stimulation time of 33 s. 3. GABA stimulated a concentration-dependent increase in the extracellular acidification rate with an EC50 of 2.0 +/- 0.2 microM (mean +/- s.e.mean, n = 7 experiments) and maximal increase (Emax) over basal response of 15.4 +/- 1.2%. 4. The sub-maximal GABA-stimulated increase in acidification rate could be potentiated by the 1,4-benzodiazepine, flunitrazepam (100 nM). The 10 nM GABA response showed the maximal benzodiazepine facilitation (GABA alone, 1.4 microV s-1, GABA + flunitrazepam, 3.8 microV s-1, mean increment over basal, n = 7). 5. The GABA-stimulated increase in acidification rate was inhibited by the GABAA antagonist, bicuculline (100 microM) (90% inhibition at 1 mM GABA). 6. The results of this study show that activation of GABAA receptors in rat cerebellar granule cells caused an increase in the extracellular acidification rate; an effect which was potentiated by benzodiazepines and inhibited by a GABAA receptor antagonist. This paper defines the conditions and confirms the feasibility of using microphysiometry to investigate GABAA receptor function in primary cultured CNS neurones. The microphysiometer provides a rapid and sensitive technique to investigate the regulation of the GABAA receptor in populations of neurones.

P-11-5 - Relationship between diazepam withdrawal signs and GABA receptor function in rats

P-11-5 - Relationship between diazepam withdrawal signs and GABA receptor function in rats

Chronic NGF treatment alters hippocampal muscarinic receptor function in rats with fimbrial transections

Chronic NGF treatment alters hippocampal muscarinic receptor function in rats with fimbrial transections

Effects of MDL 73005EF on central pre- and postsynaptic 5-HT 1A receptor function in the rat in vivo

The effects of MDL 73005EF (8-[2-(2,3-dihydro-l,4-benzodioxin-2-yl)methylamino]-8-azaspiro[4,5]decan-7,9-dione methyl sulphonate), a novel selective 5-HT 1A receptor ligand with putative anxiolytic properties, were explored using models of central pre- and postsynaptic 5-HT 1A receptor function in the male rat. MDL 73005EF dose dependently decreased the hippocampal 5-HT output measured by in vivo microdialysis in chloral hydrate-anaesthetised rats and this response was antagonised by the 5-HT 1A B receptor antagonist, pindolol. Local administration of MDL 73005EF had no effect on the hippocampal 5-HT output. MDL 73005EF failed to alter basal plasma adrenocorticotropin (ACTH) levels but, in common with pindclol, attenuated the ACTH response to the 5-HT 1A receptor agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT). In contrast to 8-OH-DPAT, MDL 73005EF significantly increased plasma prolactin but apparently not through a 5-HT receptor-mediated mechanism. The results indicate that MDL 73005EF possesses mixed 5-HT 1A receptor agonist/antagonist properties, acting as an agonist at presynaptic 5-HT 1Areceptors controlling 5-HT release and as an antagonist at postsynaptic 5-HT 1A receptors mediating ACTH release.