This study was designed to investigate the effect of diazepam on the spontaneous contraction and oxytocin induced contraction of the isolated rat uterus. Female rat (Sprague-Dawley) pretreated with oophorectomy and 4 days administration of estrogen. Weighing about 200 g, was sacrificed by cervical dislocation, and the uteruses were isolated. A longitudinal muscle strip was placed in temperature controlled (37℃) muscle chamber containing Locke's solution and myographied isometrically. Diazepam inhibited the spontaneous contraction and oxytocin induced contraction of the isolated rat uterus in a concentration-dependent manner. GABA, muscimol, a GABA A receptor agonist, bicuculline, a competitive GABA A receptor antagonist, picrotoxin, a non competitive GABA A receptor antagonist, baclofen, a GABA B receptor agonist, and delta-aminovaleric acid, a GABA B receptor antagonist, did not affect on the spontaneous and oxytocin induced contraction of the isolated rat uterus. The inhibitory actions of diazepam on the spontaneous and oxytocin induced contraction were not affected by all the GABA receptor agonists and antagonists, but exceptionally potentiated by bicuculline. This potentiation-effect by bicuculline was not antagonized by muscumol. In normal calcium PSS, addition of calcium restored the spontaneous contraction preinhibited by diazepam and recovered the contractile of oxtrocin preinhibited by diazepam. A23187, a calcium inophore, enhanced the restoration of both the spontaneous and oxytocin induced contraction by addition of calcium. In calcium-free PSS, diazepam suppressed the restoration of spontaneous motility by addition of calcium but allowed the recovery of spontaneous motility to a considerable extent. Diazepam could not inhibit some development of contractility by oxytocin in calcium-free PSS, but inhibited the increase in contractility by subsequent addition of calcium. These results suggest that the inhibitory action of diazepam on the rat uterine motility does not depend on or related to GABA receptors and that diazepam inhibits the extracellular calcium influx to suppress the spontaneous and oxytocin induced contractilities.
Animals ; Baclofen ; Bicuculline ; Calcimycin ; Calcium ; Diazepam* ; Dislocations ; Estrogens ; Female ; GABA Agonists ; GABA-A Receptor Agonists ; GABA-A Receptor Antagonists ; GABA-B Receptor Agonists ; GABA-B Receptor Antagonists ; gamma-Aminobutyric Acid ; Humans ; Muscimol ; Ovariectomy ; Oxytocin* ; Picrotoxin ; Rats* ; Receptors, GABA ; Uterus*

This study was designed to investigate the effect of GABA and related substances on the spontaneous contraction of rat small intestine. The rats (Sprague-Dawley), weighing 200-250g, were sacrificed by cervical dislocation, and the small intestine was isolated. Longitudinal muscle strips from duodenum, jejunum and ileum were suspended in Biancani's isolated muscle chambers and myographied isometrically. GABA and muscimol, a GABA A receptor agonist relaxed the duodenum and jejunum significantly, but baclofen-induced relaxation in those muscle strips negligible. The effectiveness of GABA and muscimol in various regions were the greatest on duodenum, and greater on jejunum than on ileum The effect of GABA and muscimol was antagonized by bicuculline, a competitive GABA A receptor antagonist and picrotoxin, a noncompetitive GABA A receptor antagonist. Duodenal relaxation induced by GABA and muscimol was unaffected by hexamethonium, but was prevented by tetrodotoxin. These results suggest that GABA inhibit the contractility of smooth muscle with distinct regional difference of efficacy, and the site of inhibitory action is the GABA A receptor existing at the presynaptic membrane of postganglionic excitatory nerves.
Animals ; Bicuculline ; Dislocations ; Duodenum ; GABA-A Receptor Agonists ; GABA-A Receptor Antagonists ; gamma-Aminobutyric Acid* ; Hexamethonium ; Ileum ; Intestine, Small* ; Jejunum ; Membranes ; Muscimol ; Muscle, Smooth ; Picrotoxin ; Rats* ; Receptors, GABA-A ; Relaxation ; Tetrodotoxin

BACKGROUND: This study was conducted to investigate the roles of the spinal and peripheral gamma-aminobutyric acid (GABA)-ergic systems for the mechanical hypersensitivity produced by chronic compression of the dorsal root ganglion (CCD). METHODS: CCD was performed at the left 5th lumbar dorsal root ganglion. The paw withdrawal threshold (PWT) to von Frey stimuli was measured. The mechanical responsiveness of the lumbar dorsal horn neurons was examined. GABAergic drugs were delivered with intrathecal (i.t.) or intraplantar (i.pl.) injection or by topical application onto the spinal cord. RESULTS: CCD produced mechanical hypersensitivity, which was evidenced by the decrease of the PWT, and it lasting for 10 weeks. For the rats showing mechanical hypersensitivity, the mechanical responsiveness of the lumbar dorsal horn neurons was enhanced. A similar increase was observed with the normal lumbar dorsal horn neurons when the GABA-A receptor antagonist bicuculline was topically applied. An i.t. injection of GABA-A or GABA-B receptor agonist, muscimol or baclofen, alleviated the CCD-induced hypersensitivity. Topical application of same drugs attenuated the CCD-induced enhanced mechanical responsiveness of the lumbar dorsal horn neurons. CCD-induced hypersensitivity was also improved by low-dose muscimol applied (i.pl.) into the affected hind paw, whereas no effects could be observed with high-dose muscimol or baclofen. CONCLUSIONS: The results suggest that the neuropathic pain associated with compression of the dorsal root ganglion is caused by hyperexcitability of the dorsal horn neurons due to a loss of spinal GABAergic inhibition. Peripheral application of low-dose GABA-A receptor agonist can be useful to treat this pain.
Animals ; Back Pain ; Baclofen ; Bicuculline ; GABA-A Receptor Agonists ; GABA-A Receptor Antagonists ; GABA-B Receptor Agonists ; gamma-Aminobutyric Acid ; Ganglia, Spinal ; Hyperalgesia ; Hypersensitivity* ; Muscimol ; Neuralgia ; Posterior Horn Cells ; Rats* ; Receptors, GABA ; Spinal Cord

BACKGROUND: A phosphodiesterase 5 inhibitor, sildenafil, has been effective against nociception. Several lines of evidence have demonstrated the role of the GABAergic pathway in the modulation of nociception. The impact of the GABA receptors on sildenafil was studied using the formalin test at the spinal level. METHODS: Male SD rats were prepared for intrathecal catheterization. The formalin test was induced by subcutaneous injection of formalin solution. The change in the activity of sildenafil was examined after pretreatment with GABA receptor antagonists (GABAA receptor antagonist, bicuculline; GABAB receptor antagonist, saclofen). RESULTS: Intrathecal sildenafil dose-dependently attenuated the flinching observed during phase 1 and 2 in the formalin test. The antinociceptive effect of sildenafil was reversed by the GABAB receptor antagonist (saclofen) but not by the GABAA receptor antagonist (bicuculline) in both phases. CONCLUSIONS: Intrathecal sildenafil suppressed acute pain and the facilitated pain state. The antinociception of sildenafil is mediated via the GABAB receptor, but not the GABAA receptor, at the spinal level.
Acute Pain ; Animals ; Bicuculline ; Catheterization ; Catheters ; Cyclic Nucleotide Phosphodiesterases, Type 5 ; Formaldehyde* ; GABA Antagonists ; Humans ; Injections, Subcutaneous ; Male ; Nociception ; Pain Measurement* ; Rats* ; Receptors, GABA ; Sildenafil Citrate

BACKGROUND: Androsterone is one of the major metabolites from testosterone whose clinical importance remains unclear. This study evaluated the effects of androsterone on seizure susceptibility in mouse models of epilepsy. METHODS: The efficacy of androsterone (10~200 mg/kg, i.p.) against seizures induced by various GABA receptor antagonists and glutamate receptor agonists was evaluated. RESULTS: Androsterone protected mice against seizures induced by PTZ (pentylenetetrazol), PCX (picrotoxin), and DMCM (methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate) in a dose-dependent manner. Androsterone did not protect against seizures induced by kainic acid, NMDA (N-methyl-D-aspartic acid), or 4-AP (4-aminopyridine) in mice. CONCLUSIONS: These results suggest that androsterone exhibits anticonvulsant activity that occurs largely via nongenomic mechanisms. Testosterone-derived androsterone might be an endogenous protective neuroactive steroid in the brain.
Androsterone ; Animals ; Carbolines ; Epilepsy ; GABA Antagonists ; gamma-Aminobutyric Acid ; Kainic Acid ; Mice ; N-Methylaspartate ; Receptors, Glutamate ; Seizures ; Testosterone

OBJECTIVE: Suvorexant is a novel hypnotic drug that does not interact with the conventional γ-aminobutyric acid (GABA)-A receptor. We investigated the method by which suvorexant was introduced in insomnia patients who were taking benzodiazepine receptor agonists (BzRA). METHODS: This was a retrospective study. We extracted clinical data for patients who were prescribed suvorexant and were already using BzRA. The patients were assigned to two groups, the switching and add-on groups. We assessed the suvorexant discontinuation rate at one month after the prescription of the drug. RESULTS: One hundred and nineteen patients were assigned to the switching group, and 109 were assigned to the add-on group. The add-on group exhibited a significantly higher all-cause discontinuation rate than the switching group (odds ratio, 2.7; 95% confidence interval, 1.5 to 5.0; adjusted p < 0.001). Intolerability was a significantly stronger risk factor for suvorexant discontinuation in the add-on group (22.0% vs. 7.6%, p < 0.002), and the most common adverse effect was oversedation. CONCLUSION: Our results show that the add-on of suvorexant increases the frequency of oversedation compared with switching in insomnia patients that are taking BzRA. However, this was only a preliminary retrospective study, and further studies will be required to confirm our findings.
Benzodiazepines* ; Humans ; Methods ; Orexin Receptor Antagonists ; Prescriptions ; Receptors, GABA-A* ; Retrospective Studies* ; Risk Factors ; Sleep Initiation and Maintenance Disorders*

BACKGROUND: Curcumin is traditionally used as an herbal medicine. We explored the efficacy of intrathecal curcumin in relieving both postoperative and inflammatory pain and elucidated the mechanisms of action of curcumin interacting with γ-aminobutyric acid (GABA) and opioid receptors at the spinal level. METHODS: Experimental pain was induced in male Sprague-Dawley rats via paw incision or injection of intraplantar carrageenan. After examination of the effects of intrathecal curcumin on the pain, GABA and opioid receptor antagonists were intrathecally administered to explore the involvement of GABA or opioid receptors on the effect of curcumin. Additionally, the expression levels of the GABA and opioid receptors were assessed. RESULTS: Intrathecal curcumin reduced the withdrawal threshold of both incisional surgery- and carrageenan injection-induced nociception. Intrathecal GABA and opioid receptor antagonists reversed the curcumin-mediated antinociception. Incisional surgery decreased the levels of the GABA receptors mRNA, but little changed the levels of the opioid receptors mRNA. Carrageenan injection increased the levels of the opioid receptors mRNA, but not the GABA receptors mRNA levels. Intrathecal curcumin increased or decreased the levels of GABA receptors mRNA and opioid receptors mRNA in the spinal cords of incised or carrageenan-injected rats, respectively. CONCLUSIONS: Intrathecal curcumin was effective to postoperative and inflammatory pain and such antinociception of curcumin was antagonized by both GABA and opioid receptor antagonists. Also, intrathecal curcumin altered the levels of GABA and opioid receptors. Thus, spinal GABA and opioid receptors may, respectively, be directly or indirectly involved when curcumin alleviates postoperative and inflammatory pain.
Animals ; Carrageenan ; Curcumin ; gamma-Aminobutyric Acid ; Herbal Medicine ; Humans ; Male ; Narcotic Antagonists ; Nociception ; Rats ; Rats, Sprague-Dawley ; Receptors, GABA ; Receptors, Opioid ; RNA, Messenger ; Spinal Cord

OBJECTIVETo investigate the pharmacological modulatory properties of noradrenaline in the rat spiral ganglion neuron.

METHODSNystatin perforated patch recording technique under voltage-clamp conditions was used to record the modulatory effect of noradrenaline on the current evoked by gamma-amino butyric acid (GABA) in the spiral ganglion neuron.

RESULTSThe reversal potential of the GABA response was about (- 0.78 +/- 0.05) mV (n = 8), which was almost identical to the theoretical Cl- equilibrium potential. At the holding potential of -50 mV, GABA evoked inward current (I(GABA)) over the concentration range of 0.3 to 1 micromol/L. The EC50 and Hill coefficient for GABA were (5.2 +/- 0.5) micromol/L and 1.03 (n = 26). The I(GABA) was suppressed by bicuculline, the selective GABA-A receptor antagonist, and the chloride currents evoked by GABA was inhibited by noradrenaline.

CONCLUSIONSThe result indicates that noradrenaline depressed GABA-A receptor-gated chloride currents, which may contribute to the modulatory effect of sympathetic system on auditory transmission.

Animals ; Chloride Channels ; drug effects ; GABA-A Receptor Antagonists ; pharmacology ; Neurons ; drug effects ; metabolism ; Norepinephrine ; pharmacology ; Patch-Clamp Techniques ; Rats ; Rats, Sprague-Dawley ; Receptors, GABA ; metabolism ; Spiral Ganglion ; drug effects

In the present study, the correlated activities of adjacent ganglion cells of transient subtype in response to full-field white light stimulation were investigated in the chicken retina. Pharmacological studies and cross-correlation analysis demonstrated that application of the GABA(A) receptor antagonist bicuculline (BIC) significantly down-regulated the correlation strength while increasing the firing activities. Meanwhile, application of the GABA(A) receptor agonist muscimol (MUS) potentiated the correlated activities while decreasing the firing rates. However, application of the GABA(C) receptor antagonist (1,2,5,6-Tetrahydropyridin-4-yl)methylphosphinic acid (TPMPA) did not have a consistent influence on either the firing rates or the correlation strength. These results suggest that in the chicken retina, correlated activities among neighborhood transient ganglion cells can be increased while firing activities are reduced with the activation of GABA(A) receptors. The GABA(A)-receptor-mediated inhibitory pathway may be critical for improving the efficiency of visual information transmission.
Action Potentials ; Animals ; Bicuculline ; pharmacology ; GABA-A Receptor Antagonists ; pharmacology ; Mice ; Muscimol ; pharmacology ; Phosphinic Acids ; pharmacology ; Pyridines ; pharmacology ; Receptors, GABA-A ; metabolism ; Retina ; physiology ; Retinal Ganglion Cells ; physiology ; gamma-Aminobutyric Acid

By means of whole-cell patch clamp technique, the modulatory effect of caffeine on GABA-activated currents (I(GABA)) was investigated in acutely isolated rat dorsal root ganglion (DRG) neurons. The majority of the neurons examined (113/116) were sensitive to GABA (1~1000 micromol/L). GABA activated a concentration-dependent inward current, which manifested obvious desensitization. In 58 out of 108 neurons, caffeine induced a small inward current, while in others no detectable current was observed. After the neurons were treated with caffeine (0.1~100 micromol/L) prior to the application of GABA (100 micromol/L) for 30 s, GABA-activated inward currents were obviously inhibited. Caffeine shifted the GABA dose-response curve downward and decreased the maximum response to 57% without changing K(d) value. These results indicate that the inhibitory effect is non-competitive. The pretreatment with caffeine (10 micromol/L) inhibited I(GABA) which was potentiated by diazepam (1 micromol/L). Intracellular application of H-8 almost completely abolished the inhibitory effect of caffeine on I(GABA). Because GABA can induce primary afferent depolarization (PAD), our results suggest that caffeine may be able to antagonize the effect of presynaptic inhibition of GABA in primary afferent.
Animals ; Animals, Newborn ; Caffeine ; pharmacology ; Cell Separation ; Cells, Cultured ; Electrophysiology ; GABA Antagonists ; pharmacology ; Ganglia, Spinal ; cytology ; physiology ; Neurons ; cytology ; physiology ; Patch-Clamp Techniques ; Rats ; Rats, Sprague-Dawley ; Receptors, GABA-A ; physiology ; gamma-Aminobutyric Acid ; physiology