PURPOSE: Flutamide (4-nitro-3-t-trifluoromethyl-isobutyranilide) is an androgen-receptor antagonist with typical antiandrogenic effect, used to treat androgen-dependent disorders such as prostate cancer. However, some reports noted that flutamide has direct effects to neuronal cells. It has been shown to retard the development of electrical kindling in rats. METHODS: We used the chemoconvulsant 4-aminopyridine (4-AP) and picrotoxin (PTX) in the in vitro hippocampal slice model to determine of flutamide for the suppression of epileptiform discharges. Extracellular field potential recordings were obtained from the CA3 pyramidal layer of hippocampus. RESULTS: The concentration of 30 and 100 micrometer flutamide suppressed the whole mean number of epileptiform discharges to 57.8% and 66.8% each compared with the 4-AP only slices. In 100 micrometer PTX, 10 and 30 micrometer flutamide suppressed the whole mean number of epileptiform discharges to 56.6% and 82.5% each. Intermixed with flumazenil, the anticonvulsant effect of flutamide was decreased. CONCLUSIONS: Flutamide suppressed epileptiform discharges induced by 4-AP and PTX in vitro seizure model. It suggests that flutamide influence to anti-epileptic activity by benzodiazepine site of the GABAA receptor.
4-Aminopyridine ; Benzodiazepines ; Flumazenil ; Flutamide ; Neurons ; Picrotoxin ; Prostatic Neoplasms ; Seizures

The effects of ethanol on corticostriatal synaptic transmission were examined, using extracellular recording and analysis of population spike amplitudes in rat brain slices, to study how acute ethanol intoxication impairs striatal function. Ethanol caused a decrease in population spike amplitudes in a dose dependent manner (50~200 mM). Pretreatment with picrotoxin, a gamma-amino butyric acid (GABA)A receptor antagonist, increased the population spikes but ethanol (100 mM) was still effective in decreasing the population spikes under this condition. In the presence of (DL)-2-amino-5-phosphonovaleric acid (APV), N-methyl-D-aspartate (NMDA) receptor antagonist, the inhibitory action of ethanol on population spikes was not shown. These results suggest that ethanol inhibits the glutamatergic corticostriatal synaptic transmission through blockade of NMDA receptors.
Animals ; Brain ; Butyric Acid ; Ethanol* ; N-Methylaspartate* ; Picrotoxin ; Rats* ; Receptors, Glutamate ; Receptors, N-Methyl-D-Aspartate ; Synaptic Transmission*

Taurine has a number of beneficial pharmacological actions in the brain such as anxiolytic and neuroprotective actions. We explored to test whether taurine could be transported to the central nervous system through the intranasal route. Following intranasal administration of taurine in mice, elevated plus maze test, activity cage test and rota rod test were carried out to verify taurine’s effect on anxiety. For the characterization of potential mechanism of taurine’s anti-anxiety action, mouse convulsion tests with strychnine, picrotoxin, yohimbine, and isoniazid were employed. A significant increase in the time spent in the open arms was observed when taurine was administered through the nasal route in the elevated plus maze test. In addition, vertical and horizontal activities of mice treated with taurine via intranasal route were considerably diminished. These results support the hypothesis that taurine can be transported to the brain through intranasal route, thereby inducing anti-anxiety activity. Taurine’s anti-anxiety action may be mediated by the strychnine-sensitive glycine receptor as evidenced by the inhibition of strychnine-induced convulsion.
Administration, Intranasal ; Animals ; Anxiety ; Arm ; Brain ; Central Nervous System ; Isoniazid ; Mice ; Picrotoxin ; Receptors, Glycine ; Seizures ; Strychnine ; Taurine ; Yohimbine

Transcutaneous electrical nerve stimulation(TENS), acupuncture-needling, and electroacupuncture are useful non-ablative methods in medical practice for relief of pain. These procedures appear to work by causing an increased discharge in afferent nerve fibers which in turn modifies the transmission of impulses in pain pathways. It is known that the mechanism of analagesic effect via these maneuvers are variable depending on the stimulating parameters. For example, the endogenous opioid system is profoundly related to the mechanism when a peripheral nerve stimulation is applied with parameters of low frequency and high intensity. However, when stimulated with parameters of high frequency and high intensity, the reduced activity of dorsal horn neurons is only slightly reversed by a systemic administration of naloxone, a specific opiate antagonist. Thus, the present study was performed to investigate the neurotransmitter that concerns the mechanism of peripheral nerve stimulation with parameters of high frequency and high intensity. We used an iontophoretic application of antagonists of possible related neurotransmitters. The dorsal horn neuron activity which was evoked by squeezing the peripheral cutaneous receptive field, was recorded as an index of pain with a microelectrode at the lumbo-sacral spinal cord. Naloxone, picrotoxin and strychnine were applied at 200nA during a period of conditioning nerve stimulation. We observed the effects of these drugs on the change of dorsal horn neuron activities. The main results of the experiment can be summarized as follows. The spontaneous activity of dorsal horn neurons increased in the presence of glutamate and decreased with GABA. It did not change with naloxone, picrotoxin or strychnine. When naloxone was applied iontophoretically during peripheral nerve stimulation, there was no statistically significant analgesic effect compared with that of the control group. When picrotoxin was applied iontophoretically during peripheral nerve stimulation, the analgesic effect was reduced. When strychnine was applied, the analgesic effect was reduced but did not show a statistically significant difference with the control group. These results suggested that the GABAergic system may have been partially related in the analgesic action of peripheral nerve stimulation with parameters of high frequency and high intensity.
Animal ; Cats ; *Conditioning (Psychology) ; Female ; Iontophoresis ; Male ; Naloxone/*pharmacology ; Neurons/drug effects ; Picrotoxin/*pharmacology ; Spinal Cord/cytology/*drug effects ; Strychnine/*pharmacology ; *Transcutaneous Electric Nerve Stimulation

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

AIMTo observe the role of melatonin receptor and GABAA receptor in sleeping time prolonged by melatonin in mice.

METHODSThe absence of the righting reflex was considered as the sleep onset and the duration of the loss of the righting reflex was recorded as the sleeping time. The effects of receptor agonist and antagonist on hypnotic activity of melatonin were studied in the paper.

RESULTSPrazosin hydrochloride, the blocker of melatonin 3 receptor, didn't affect the sleeping time prolonged by melatonin in mice. GABA, the endogenous agonist of GABA receptor, significantly potentiated the hypnotic activity of melatonin. When picrotoxin, the ligand of picrotoxin site on GABAA receptor, used together with melatonin, it significantly antagonized the sleeping time prolonged by melatonin, however, bicuculline, the specific antagonist of GABA binding site in GABAA receptor, didn't affect the hypnotic activity of melatonin in mice.

CONCLUSIONMelatonin does not exhibit its potentiation sleeping time in mice through melatonin 3 receptor. Hypnotic activity of melatonin may be mediated through picrotoxin site on GABAA receptor.

Animals ; Bicuculline ; pharmacology ; Male ; Melatonin ; physiology ; Mice ; Mice, Inbred Strains ; Picrotoxin ; pharmacology ; Prazosin ; pharmacology ; Receptors, GABA-A ; physiology ; Receptors, Melatonin ; physiology ; Sleep ; physiology

Previous studies showed that a mixture, Coriaria Lactone (CL), extracted from a traditional Chinese herb Loranthus Parasiticus Mer, had a great excitatory influence on the nervous system, resulting in seizure. But what component in CL causes seizure is unclear. Tutin is a pure chemical component derived from CL. The present experiments were carried out to test if tutin has any epileptogenic action and to preliminarily study the mechanism underlying that action in vitro. The electrical activity of CA1 pyramidal cells, population spikes (PS), evoked by stimulation of the Schaffer collaterals in rat hippocampal slices was recorded extracellularly. The effects of tutin on the PS and the antagonistic actions of CNQX and AP-5 on the tutin-induced effects were investigated. The results are as follows. (1) Superfusion with 40, 30 and 20 microg/ml tutin caused significant increase in the amplitude and number of PS waves evoked by stimulating the Schaffer collaterals. Thirty minutes after superfusion of tutin, the amplitude of the first wave of the PSs was increased by (388.7+/-0.1)%, (317.2+/-19.1)% and (180.9+/-11.6)% in each of the above three groups, respectively, compared with the control (for each group, n=5, P<0.05). (2) With increase in amplitude, the PS number was increased to 4~11 waves from a single wave in the control and manifested multiple epileptiform discharges 30 min superfusion with tutin. (3) Spontaneous epileptiform discharges of CA1 pyramidal cells were obtained in 9 out of 34 cases after tutin superfusion. (4) The tutin-induced multiple epileptiform discharges of the CA1 pyramidal cells were completely blocked by CNQX, in aspects of both amplitude and number of the PS. Following the application of AP-5, the increase in the wave number of the tutin-induced epileptiform discharges was inhibited but the increase in the amplitude of the discharges was not significantly affected. These results indicate that tutin can induce typical multiple epileptiform discharges of CA1 pyramidal cells in rat hippocampal slices and might be used as an efficient epileptogenic agent, and that the excitable glutamate receptors, especially the non-NMDA receptors, may participate in the genesis of tutin-induced epileptiform discharges.
Animals ; Electrophysiology ; Epilepsy ; chemically induced ; physiopathology ; Female ; Hippocampus ; physiopathology ; Male ; Picrotoxin ; analogs & derivatives ; Pyramidal Cells ; physiopathology ; Rats ; Rats, Sprague-Dawley ; Sesquiterpenes ; pharmacology

Background: Several studies have suggested that the spinal cord may be an important site of anesthetic action and have established that general anesthetics potentiate the effects of GABA at the GABAA receptor. It was, therefore, hypothesized that the suppression of nocifensive movements during anesthesia is due to an enhancement of GABAA receptor-mediated transmission. Therefore, the aim of this study was to determine behaviorally whether intrathecal GABA, glycine, or opioid receptor antagonists may change the anesthetic effect of isoflurane and enflurane. Methods: The minimal alveolar concentration (MAC) of isoflurane and enflurane was determined in Sprague-Dawley rats, by the tail-clamp technique. First, MAC was determined and then concentration of each inhalation agent was increased by 0.2% from the sub-MAC level. Moving latencies were observed after the intrathecal administration of each receptor antagonist. Rectal temperature was measured and maintained at a steady level during the experiment. Results: The spinal antinociceptive effects of isoflurane and enflurane were significantly reversed by the GABAA receptor antagonist bicuculline and picrotoxin (P < 0.05). The rectal temperature was well maintained within the range of 37-39 degrees C. Conclusions: Our results suggest that the general anesthesia induced by isoflurane and enflurane, which are similar in terms of their action mechanism, is likely to be related to the spinal GABAA receptor system.
Anesthesia ; Anesthesia, General ; Anesthetics ; Anesthetics, General ; Animals ; Bicuculline ; Enflurane* ; gamma-Aminobutyric Acid ; Glycine ; Inhalation ; Isoflurane* ; Picrotoxin ; Rats* ; Rats, Sprague-Dawley ; Receptors, Opioid ; Spinal Cord

The expression of the c-fos and krox-24 (immediate early genes: IEGs) and the BDNF (late response gene) were investigated by convulsants such as kainate (KA, 200 micrometer), N-methyl-D-aspartate (NMDA, 10 mM), glutamate (GLU, 2 mM), and picrotoxin (PTX, 20 micrometer in the rat C6 glioma cells. In addition, the changes of their expression patterns were investigated by the anticonvulsants such as a NMDA antagonist MK-801, phenytoin, phenobarbiw, diazepam, and newer antiepileptic drugs like felbamate and gabapentin. NMDA induced c-fos and krox-24 expromiom were decreased spatially by the anticonvulsants. KA, NMDA, GLU, and PTX-induced BDNF expression were increased by the anticonvulsants. These results imply the molecular basis of the anticonvulsant action mechanism lies in differential and coordinated transcriptional regulation of IEGs.
Animals ; Anticonvulsants* ; Brain-Derived Neurotrophic Factor ; Convulsants ; Diazepam ; Dizocilpine Maleate ; Genes, Immediate-Early* ; Glioma ; Glutamic Acid ; Kainic Acid ; N-Methylaspartate ; Phenytoin ; Picrotoxin ; Rats

BACKGROUND: The influence of gamma-aminobutyric acid(GABA), which is well-known as a major inhibitory neurotransmitter in central nervous system, on secretion of catecholamines(CA) was investigated in the isolated perfused rat adrenal gland. METHODS: Mature male Sprague-Dawley rats were anesthetized with ether. Ther adrenal gland was isolated by the methods f Wakade. A cannula used for perfusion of the adrenal gladn was inserted into the distal end of the renal vein. The adrenal gland, along with ligated blood vessels and the cannula, was carefully removed from the animal and placed on a platform of a leucite chamber. RESULTS: GABA given into an adrenal vein of the rat produced markedly secretion of CA from the adrenal gland. Tachyphylaxis to the relesing effect of CA evoked by GABA was observed. The secretory effect of CA evoked by GABA was attenuated singnificantly by pretreatment with mecamylamine or atropine. Ouabain inhibited greatly the secretory response of GABA. When omitting the external potassium ion, the basal release of CA was increased. During this period GABA no longer revealed the increase in CA release. CA secretion evoked by GABA was blocked significantly by perfusion of calcium-free Krebs solution containing 5mMEGTA for 30-min. Pretreatment with bicuculline or picrotoxin inhibited CA secretion evoked by GABA as well as ACh. ACh-evoked CA release was potentiated by GABA infusion(400ug/30min). CONCLUSION: The experimental findings suggest that GABA causes the secretory effect of CA in a fashion of external calcium and potassium iosn-dependence, and that this releasing effect of CA induced by GABA may be exterted by stimulation of GABAergic A-reccptors located on adrenomedullary chromaffine cell, which is likely associated with cholinergic receptor activation evoked CA secretion.
Adrenal Glands* ; Animals ; Atropine ; Bicuculline ; Blood Vessels ; Calcium ; Catheters ; Central Nervous System ; Ether ; gamma-Aminobutyric Acid ; Humans ; Male ; Mecamylamine ; Neurotransmitter Agents ; Ouabain ; Perfusion ; Picrotoxin ; Potassium ; Rats* ; Rats, Sprague-Dawley ; Renal Veins ; Tachyphylaxis ; Veins