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*

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

PURPOSE: The inhibition of phosphodiesterase 5 produces an antinociception through the increase of cyclic guanosine monophosphate (cGMP), and increasing cGMP levels enhance the release of gamma-aminobutyric acid (GABA). Furthermore, this phosphodiesterase 5 plays a pivotal role in the regulation of the vasodilatation associated to cGMP. In this work, we examined the contribution of GABA receptors to the effect of sildenafil, a phosphodiesterase 5 inhibitor, in a neuropathic pain rat, and assessed the hemodynamic effect of sildenafil in normal rats. MATERIALS AND METHODS: Neuropathic pain was induced by ligation of L5/6 spinal nerves in Sprague-Dawley male rats. After observing the effect of intravenous sildenafil on neuropathic pain, GABAA receptor antagonist (bicuculline) and GABAB receptor antagonist (saclofen) were administered prior to delivery of sildenafil to determine the role of GABA receptors in the activity of sildenafil. For hemodynamic measurements, catheters were inserted into the tail artery. Mean arterial pressure (MAP) and heart rate (HR) were measured over 60 min following administration of sildenafil. RESULTS: Intravenous sildenafil dose-dependently increased the withdrawal threshold to the von Frey filament application in the ligated paw. Intravenous bicuculline and saclofen reversed the antinociception of sildenafil. Intravenous sildenafil increased the magnitude of MAP reduction at the maximal dosage, but it did not affect HR response. CONCLUSION: These results suggest that sildenafil is active in causing neuropathic pain. Both GABAA and GABAB receptors are involved in the antinociceptive effect of sildenafil. Additionally, intravenous sildenafil reduces MAP without affecting HR.
Animals ; Baclofen/analogs & derivatives/pharmacology ; Bicuculline/pharmacology ; Blood Pressure/drug effects ; Dose-Response Relationship, Drug ; Heart Rate/drug effects ; Hemodynamics/drug effects ; Male ; Neuralgia/*drug therapy ; Pain Threshold/drug effects ; Phosphodiesterase Inhibitors/*therapeutic use ; Piperazines/*therapeutic use ; Purines/therapeutic use ; Rats ; Rats, Sprague-Dawley ; Receptors, GABA-A/antagonists & inhibitors/physiology ; Receptors, GABA-B/antagonists & inhibitors/physiology ; Sulfones/*therapeutic use

<b>OBJECTIVEb>To investigate the protective mechanism of neuroactive steroid allopregnanolone on N-methyl-D-aspartate (NMDA) induced toxicity in primary mouse cortical neurons.

<b>METHODSb>Primary cultured mouse cortical neurons were subjected to allopregnanolone, the expression of beta-aminobutyric acid receptor beta2 subunit (beta2-GABA-R) mRNAs was detected by RT-PCR and Akt phosphorylation was assayed by Western blot using Akt-phosphoserine 473-specific antibody. After the cultured mouse cortical neurons were pretreated with or without allopregnanolone prior to treatment with NMDA , DNA isolated was analyzed by agarose gel electrophoresis and proteins collected were analyzed by Western blot with anti-cleaved-PARP, anti-cleaved caspase-3, and anti-cleaved caspase-9 antibodies.

<b>RESULTSb>When cultured mouse cortical neurons were exposed to allopregnanolone both the expression of beta2-GABA-R mRNAs and Akt phosphorylation increased. Allopregnanolone inhibited the NMDA-induced apoptosis and decreased the level of active-PARP, active-caspase-3 and active-caspase-9 notably at a final concentration of 5 x 10(6) mol/L.

<b>CONCLUSIONb>Pretreatment with allopregnanolone may be neuroprotective on NMDA-induced neuronal cells apoptosis by increasing beta2-GABA-R expression and Akt phosphorylation.

Animals ; Animals, Newborn ; Apoptosis ; drug effects ; Caspase 3 ; metabolism ; Caspase 9 ; metabolism ; Cerebral Cortex ; cytology ; Mice ; N-Methylaspartate ; antagonists & inhibitors ; toxicity ; Neurons ; cytology ; Neuroprotective Agents ; pharmacology ; Poly (ADP-Ribose) Polymerase-1 ; Poly(ADP-ribose) Polymerases ; metabolism ; Pregnanolone ; pharmacology ; Primary Cell Culture ; RNA, Messenger ; genetics ; metabolism ; Receptors, GABA-B ; genetics ; metabolism