Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Chloride Channel Agonists”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 343 records · Page 19Linked to original sources
PubMed1991

Effects of calcium channel agonists (BAY K 8644, CGP28392 and YC-170) on 45Ca uptake by rat uterine segments.

The characteristics of the stimulating effects of the calcium channel agonists BAY K 8644, CGP28392 and YC-170 on 45Ca uptake by rat uterine segments were investigated. BAY K 8644, CGP28392 and YC-170 caused about 150, 100 and 150% increase, respectively in the 45Ca uptake induced by 20 mM KCl. The ED50 values of BAY K 8644, CGP28392 and YC-170 were 1.8 X 10(-9), 2.5 X 10(-8) and 9.8 X 10(-9) M, respectively. These agonists had little effect on the 45Ca uptake induced by 10(-6) M acetylcholine. They also did not affect the basal 45Ca uptake. Their enhancing effects were blocked by the Ca channel antagonist nitrendipine. We conclude that rat uterine segments have voltage-sensitive Ca channels that are stimulated by Ca channel agonists (BAY K 8644, CGP28392 and YC-170) under depolarizing conditions and that the characteristics of the stimulating effects of CGP28392 and YC-170 on 45Ca uptake by rat uterine segments are qualitatively the same as those of BAY K 8644.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1999

Lack of effect of McN-A-343 on membrane current and contraction in guinea pig ventricular myocytes.

We asked whether agonist occupancy of M(1) muscarinic receptor (mAChR) causes increased L-type Ca(2+) [I(Ca(L))] and contractions in ventricular myocytes. Voltage-clamp pulses evoked I(Ca(L)) in guinea pig ventricular myocytes superfused with Tyrode's solution (22-24 degrees C). The mAChR agonists carbachol (Cch, nonselective), McN-A-343 (McN, M(1)-selective), and oxotremorine (Oxo, M(2)-selective) were tested at 0.1 mM. None of these agonists affected basal I(Ca(L)). McN did not change isoproterenol-stimulated I(Ca(L)) in 13 of 15 cells. The slight decrease in two cells was not muscarinic because atropine (1 microM) did not antagonize it. Carbachol or Oxo decreased isoproterenol-stimulated I(Ca(L)) by 87 +/- 6.7 (n = 8 cells) and 49 +/- 9.0% (n = 4 cells), respectively. Atropine blocked inhibition by Cch or Oxo. External stimulation evoked contractions of single myocytes (35 degrees C). McN increased contraction in 1 of 22 cells stimulated at 0.2 Hz and in 0 of 16 cells stimulated at 1.0 Hz. Carbachol significantly increased contraction in 10 of 15 cells at 0.2 Hz and in 8 of 10 cells at 1.0 Hz stimulus frequency. Summarily, the M(1)-selective agonist McN had a negligible role to regulate I(Ca(L)). The antiadrenergic effect of mAChR agonists is attributable to M(2) receptor occupancy. That Cch, but not McN, increased cell shortening excludes participation of M(1) mAChR in the stimulant effect of Cch on guinea pig ventricular myocyte contractions.

(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethy↗
PubMed2001

Covalent and noncovalent interactions mediate metabotropic glutamate receptor mGlu5 dimerization.

Some, perhaps all, G protein-coupled receptors form homo- or heterodimers. We have shown that metabotropic glutamate receptors are covalent dimers, held together by one or more disulfide bonds near the N terminus. Here we report how mutating cysteines in this region affect dimerization and function. Covalent dimerization is preserved when cysteines 57, 93, or 99 are mutated but lost with replacement at 129. Coimmunoprecipitation under nondenaturing conditions indicates that the C[129]S mutant receptor remains a dimer, via noncovalent interactions. Both C[93]S and C[129]S bind [3H]quisqualate, whereas binding to C[57]S or C[99]S mutants is absent or greatly attenuated. The C[93]S and C[129]S receptors have activity similar to wild-type when assayed by fura-2 imaging of intracellular calcium in human embryonic kidney cells or electrophysiologically in Xenopus laevis oocytes. In contrast, C[57]S or C[99]S are less active in both assays but do respond with higher glutamate concentrations in the oocyte assay. These results demonstrate that 1) covalent dimerization is not critical for mGlu5 binding or function; 2) mGlu5 remains a noncovalent dimer even in the absence of covalent dimerization; and 3) high-affinity binding requires Cys-57 and Cys-99.

Animals↗
PubMed1993

[Estimation of free calcium level within synaptosomes by using fura-2 and the effect of calcium channel agonist and antagonist].

The cytosolic free calcium concentration [Ca2+]i in synaptosomes was determined with the fluorescent indicator fura-2, the effects of calcium channel agonist and antagonist on intracellular Ca2+ level were studied. The cytosolic ionized calcium concentrations in resting status were between 200 nmol/L and 400 nmol/L. Cytosolic Ca2+ was elevated following increases in Ca2+ concentration in the medium, plasma membrane depolarizations induced by KCl, and the addition of glutamate and NMDA. On the other hand, the increase of cytosolic Ca2+ induced by KCl was decreased by verapamil and that induced by NMDA was decreased by MgCl2. A few critical problems in [Ca2+]i detection were also discussed.

Animals↗
PubMed1995

Expression of cystic fibrosis transmembrane conductance regulator in human gallbladder epithelial cells.

BACKGROUND: Hepatobiliary complications in cystic fibrosis result predominantly from lesions of the biliary epithelium. These abnormalities affect the intrahepatic as well as extrahepatic bile ducts and the gallbladder. The protein cystic fibrosis transmembrane conductance regulator (CFTR), the gene product defective in cystic fibrosis, functions as a cAMP-activated chloride channel in the plasma membrane. As such, it may represent an important driving force for fluid transport across the epithelium. EXPERIMENTAL DESIGN: The purpose of this study was to investigate the expression of CFTR in human gallbladder epithelial cells and to examine the chloride ion transport properties of these cells. Immunolocalization was performed on tissue sections. The reverse transcription-PCR was used to analyze the expression of CFTR mRNA in freshly isolated and cultured gallbladder epithelial cells. The CFTR protein was detected by Western blotting and immunoprecipitation. The chloride ion transport properties of the cells were determined by 36Cl efflux studies. RESULTS: The CFTR protein was immunodetected in human gallbladder in situ and localized predominantly to the apical membrane of epithelial cells. High levels of CFTR mRNA and protein were maintained in gallbladder epithelial cells in primary cultured. Glycosylated forms of CFTR were present as confirmed by treatment with N-glycanase. Chloride efflux was stimulated by Ca(++)-dependent pathways but more intensely by cAMP-dependent pathways. Stimulation of chloride efflux by agonist of the cAMP-pathway was inhibited by diphenylamine carboxylic acid, a chloride channel blocker. Two physiologically active peptides--acting via cAMP, vasoactive intestinal peptide, and secretin--also stimulated chloride efflux in vitro. CONCLUSIONS: Our results are consistent with a high expression of endogenous functional CFTR protein in human gallbladder epithelial cells. Physiologically active peptides, vasoactive intestinal peptide and secretin, stimulate chloride conductance in these cells. These findings indicate that CFTR play an important role in the pathophysiology of the biliary epithelium, including the gallbladder epithelium.

Base Sequence↗
PubMed1989

On the GABAA receptor: a molecular modeling approach.

Bicuculline methobromide, a complex alkaloid, antagonizes in some unknown manner the action of GABA, an important inhibitory transmitter in the CNS. To help understand the mechanism of this antagonism we have employed molecular modeling techniques to assess the similarity and difference between this antagonist and GABA plus four direct GABA agonists. Topological and electronic charge congruence between these five molecules was examined in great detail. It was found that each of the five molecules has three clearly defined atoms that serve as attachment points at the GABAA receptor site. It is hypothesized that an additional negatively charged atom on bicuculline serves as an additional point of attachment that blocks the nearby chloride ion channel. The model presented offers an explanation of why muscimol acts as a better agonist than GABA as well as rationalizing why (+)-bicuculline acts as an antagonist but (-)-bicuculline does not.

Bicuculline↗
PubMed1989

A progesterone metabolite enhances the activity of the GABAA receptor complex at the pituitary level.

The interaction of 5 alpha-pregnane-3 alpha-ol-20-one (5 alpha 3 alpha P), a progesterone metabolite, with the GABAA receptor chloride channel complex was investigated at the pituitary level. In nanomolar concentrations this steroid potentiated the inhibitory effect of muscimol (a GABAA agonist) on prolactin release from rat pituitary cells in culture. In micromolar concentrations 5 alpha 3 alpha P had a direct inhibitory effect, similar to that of muscimol, with an IC50 value of 370 nM. This effect was antagonized by bicuculline, a GABAA antagonist, and by picrotoxin, a chloride ion channel blocker. Its reduced isomer, 5 alpha 3 beta P, and progesterone (Pg) were devoid of activity. Using [35S]t-butylbicyclophosphorothionate ([35S]TBPS) as a ligand, we demonstrated, for the first time, specific barbiturate sites on pituitary membranes, similar to those of the central nervous system, with a Kd value of 25 nM and a Bmax value of 62 fmol/mg protein. 5 alpha 3 alpha P inhibited the binding of [35S]TBPS. In contrast, its 3 beta isomer was inactive. These data show that 5 alpha 3 alpha P enhanced the activity of the GABAA receptor complex at the pituitary level and suggest that its inhibitory effect on prolactin release might be mediated by the barbiturate site or by a closely related site.

5-alpha-Dihydroprogesterone↗
PubMed2002

Hyperekplexia: a treatable neurogenetic disease.

Hyperekplexia is primarily an autosomal dominant disease characterized by exaggerated startle reflex and neonatal hypertonia. It can be associated with, if untreated, sudden infant death from apnea or aspiration pneumonia and serious injuries and loss of ambulation from frequent falls. Different mutations in the alpha1 subunit of inhibitory glycine receptor (GLRA1) gene have been identified in many affected families. The most common mutation is Arg271 reported in at least 12 independent families. These mutations uncouple the ligand binding and chloride channel function of inhibitory glycine receptor and result in increased excitability in pontomedullary reticular neurons and abnormal spinal reciprocal inhibition. Three mouse models from spontaneous mutations in GLRA1 and beta subunit of inhibitory glycine receptor (GLRB) genes and two transgenic mouse models are valuable for the study of the pathophysiology and the genotype-phenotype correlation of the disease. The disease caused by mutation in GLRB in mice supports the notion that human hyperekplexia with no detectable mutations in GLRA1 may harbor mutations in GLRB. Clonazepam, a gamma aminobutyric acid (GABA) receptor agonist, is highly effective and is the drug of choice. It enhances the GABA-gated chloride channel function and presumably compensates for the defective glycine-gated chloride channel in hyperekplexia. Recognition of the disease will lead to appropriate treatment and genetic counseling.

Animals↗
PubMed1997

Induction of bradykinin B1 receptors in rat colonic epithelium.

1. Des-Arg9 bradykinin (DAB), a classical B1-kinin receptor agonist was without effect when applied to the basolateral surface of rat isolated colon epithelium. Three hours after tissues were isolated DAB caused, after a delay of up to 2 min, a maintained increase of short circuit current (SCC). 2. The SCC increase in colonic epithelia, mounted in vitro for three hours, caused by DAB was due to electrogenic chloride secretion as the current increase was reversed by frusemide and did not occur in the absence of cystic fibrosis transmembrane conductance regulator (CFTR) chloride channels. The EC50 for DAB was approximately 50 nM. 3. An inhibitor of transcription (actinomycin D) and of translation (cycloheximide) prevented the appearance of DAB sensitivity without affecting the responses to another secretagogue (forskolin). 4. The classical B1-kinin receptor antagonist, Leu8-des-Arg9 bradykinin, was shown to be an agonist in rat colon epithelium. Other B1-kinin receptor antagonists (des-Arg10-Hoe 140 and R-715) inhibited the responses to DAB in 'aged' colonic epithelia, and the inhibition was easily surmounted by increasing the concentration of DAB. 5. Response to DAB did not appear to involve to any significant extent, the formation of prostaglandins, leukotrienes, histamine or nitric oxide. Furthermore, no neuronal involvement was apparent in the stripped colonic preparations. The responses to DAB were not significantly different in epithelia taken from different parts of the distal colon. 6. The differences between the responses of the colonic epithelium to B1- and B2-kinin receptor agonists are discussed.

Animals↗
PubMed1997

GABAA receptor antagonists reduce acute opiate withdrawal in isolated tissue.

1. The effect exerted by GABAA receptor agonists and antagonists on the acute opiate withdrawal induced by mu and k receptor agonists were investigated in vitro. 2. Following a 4 min in vitro exposure to morphine (less selective mu agonist), DAGO (highly selective mu agonist) and U50-488H (highly selective k agonist) the guinea-pig isolated ileum exhibited a strong contracture after the addition of naloxone. 3. Bicuculline (1 x 10(-5)-5 x 10(-5)-1 x 10(-4) M), a GABAA receptor antagonist, injected 10 min before or after the opioid agonists was able dose-dependently to antagonize the naloxone-induced contracture after exposure to mu (morphine and DAGO) and k (U50-488H) opiate agonists. 4. Furthermore, picrotoxin (1 x 10(-5)-5 x 10(-5)-1 x 10(-4) M), an antagonist of GABA-linked chloride channels, was able to exert the same effects. 5. Muscimol (1 x 10(-5)-5 x 10(-5)-1 x 10(-4) M), a GABAA receptor agonist, was able to increase dose dependently both mu and k opiate withdrawal. 6. The data indicate that both GABAA receptor agonists and antagonists are able to control opiate withdrawal in vitro suggesting an important functional interaction between GABAergic system and the opioid withdrawal both at the mu and k receptor level.

Animals↗
PubMed2002

Glycine blocks the increase in intracellular free Ca2+ due to vasoactive mediators in hepatic parenchymal cells.

Recently, glycine has been shown to prevent liver injury after endotoxin treatment in vivo. We demonstrated that ethanol and endotoxin stimulated Kupffer cells to release PGE(2), which elevated oxygen consumption in parenchymal cells. Because glycine has been reported to protect renal tubular cells, isolated hepatocytes, and perfused livers against hypoxic injury, the purpose of this study was to determine whether glycine prevents increases in intracellular free Ca(2+) concentration ([Ca(2+)](i)) in hepatic parenchymal cells by agonists released during stress, such as with PGE(2) and adrenergic hormones. Liver parenchymal cells isolated from female Sprague-Dawley rats were cultured for 4 h in DMEM/F12 medium, and [Ca(2+)](i) in individual cells was assessed fluorometrically using the fluorescent calcium indicator fura 2. PGE(2) caused a dose-dependent increase in [Ca(2+)](i) from basal values of 130 +/- 10 to maximal levels of 434 +/- 55 nM. EGTA partially prevented this increase, indicating that either extracellular calcium or agonist binding is Ca(2+) dependent. 8-(Diethylamino)octyl 3,4,5-trimethoxybenzoate (TMB-8), an agent that prevents the release of Ca(2+) from intracellular stores, also partially blocked the increase in [Ca(2+)](i) caused by PGE(2), suggesting that intracellular Ca(2+) pools are involved. Together, these results are consistent with the hypothesis that both the intracellular and extracellular Ca(2+) pools are involved in the increase in [Ca(2+)](i) caused by PGE(2). Interestingly, glycine, which activates anion (i.e., chloride) channels, blocked the increase in [Ca(2+)](i) due to PGE(2) in a dose-dependent manner. Low-dose strychnine, an antagonist of glycine-gated chloride channel in the central nervous system, partially reversed the inhibition by glycine. When extracellular Cl(-) was omitted, glycine was much less effective in preventing the increase in [Ca(2+)](i) due to PGE(2). Phenylephrine, an alpha(1)-type adrenergic receptor agonist, also increased [Ca(2+)](i), as expected, from 159 +/- 20 to 432 +/- 43 nM. Glycine also blocked the increase in [Ca(2+)](i) due to phenylephrine, and the effect was also reversed by low-dose strychnine. Together, these data indicate that glycine rapidly blocks the increase in [Ca(2+)](i) in hepatic parenchymal cells due to agonists released during stress, most likely by actions on a glycine-sensitive anion channel and that this may be a major aspect of glycine-induced hepatoprotection.

Adrenergic alpha-Agonists↗
PubMed1988

Kinetic analysis of glutamate-induced chloride current in Aplysia neurones: a 'concentration clamp' study.

L-Glutamate (Glu) applied by the 'concentration clamp' technique to isolated neurones of Aplysia induced a chloride current (ICl) by activating a single population of the channel. The concentration-response curve for the peak ICl gave a dissociation constant of 1.3 x 10(-4) M and a Hill coefficient of 1.8. The current-voltage relationship was linear in the voltage range examined (-60 to +10 mV). The activation phase of the ICl followed a single-exponential time course and desensitization was complete with a double-exponential time course. The time constants for activation and desensitization decreased with increasing concentrations of Glu but were voltage-independent. The process of recovery from desensitization was also double-exponential. The single-channel conductance estimated by ensemble noise analysis was 50 +/- 4.7 pS (n = 4). These results suggest that the Glu receptor-Cl channel complex in Aplysia neurones consists of a single population with two binding sites for the agonist.

Animals↗
PubMed1988

Calcium-dependent glutamate cytotoxicity in a neuronal cell line.

Membranes from the neuroblastoma x embryonic retina cell hybrid cell line, N18-RE-105, bind L-[3H]glutamate with a pharmacologic profile consistent with a 'quisqualate-type' brain L-glutamate receptor. We describe here the cytotoxic effect of L-glutamate receptor agonists on intact N18-RE-105 cells. Cytotoxicity was quantitated by measurement of the release of the cytosolic enzyme, lactate dehydrogenase, into the culture medium after addition of L-glutamate and its analogs to the cell culture medium. L-Glutamate (10 mM) and its confirmationally restricted analogs, quisqualate (1 mM) and ibotenate (10 mM), caused cell lysis. In contrast, similar analogs which do not bind to N18-RE-105 cell membranes (kainic acid, N-methyl-D,L-aspartic acid and gamma-aminobutyric acid) were not cytotoxic. L-Glutamate-induced cytotoxicity was eliminated when calcium-free medium was used. Addition of inorganic or organic calcium channel antagonists also reduced the cytotoxicity of L-glutamate, even when 1.8 mM calcium was present in the medium. Cadmium chloride (10 microM) completely blocked L-glutamate toxicity, whereas manganese chloride (150 microM) and lanthanum chloride (25 microM) reduced toxicity by greater than 50%. Dihydropyridine voltage-sensitive calcium channel agonists or antagonists, had little or no significant effect on L-glutamate-induced toxicity. In contrast, the verapamil derivatives, D600 and D888, and the diltiazem derivative, MDL 12,330A reduced L-glutamate toxicity by greater than 50%. These results suggest that a subtype of voltage-sensitive calcium channels is involved in the mechanism of L-glutamate receptor mediated cytotoxicity in this cell line.

Calcium↗
PubMed1992

cAMP-dependent activation of small-conductance Cl- channels in HT29 colon carcinoma cells.

The present study was performed to examine the conductance properties in the colon carcinoma cell line HT29 and the activation of Cl- channels by cAMP. A modified cell-attached nystatin patch-clamp technique was used, allowing for the simultaneous recording of the cell membrane potential (PD) and the conductance properties of the cell-attached membrane. In resting cells, PD was -56 +/- 0.4 mV (n = 294). Changing the respective ion concentrations in the bath indicate that these cells possess a dominating K+ conductance and a smaller Cl- conductance. A significant non-selective cation conductance, which could not be inhibited by amiloride, was only observed in cells examined early after plating. The K+ conductance was reversibly inhibited by 1 - 5 mmol/l Ba2+. Stimulation of the cells by the secretagogues isoproterenol and vasointestinal polypeptide (VIP) depolarized PD and induced a Cl- conductance. Similar results were obtained with compounds increasing cytosolic cAMP: forskolin, 3-isobutyl-1-methylxanthine, cholera toxin and 8-bromoadenosine cyclic 3',5'-monophosphate (8-Br-cAMP). VIP (1 nmol/l, n = 10) and isoproterenol (1 mumol/l, n = 12) depolarized the cells dose-dependently and reversibly by 12 +/- 2 mV and 13 +/- 2 mV. The maximal depolarization was reached after some 20 s. The depolarization was due to increases in the fractional Cl- conductance. Simultaneously the conductance of the cell-attached membrane increased from 155 +/- 31 pS to 253 +/- 40 pS (VIP, n = 4) and from 170 +/- 43 pS to 268 +/- 56 pS (isoproterenol, n = 11), reflecting the gating of Cl- channels in the cell-attached membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Agonists↗
PubMed1991

Reversal of alcohol dependence and tolerance by a single administration of flumazenil.

Chronic exposure to ethanol is associated with the development of tolerance to the acute effects of ethanol and a withdrawal syndrome characterized by anxiety and seizure susceptibility. In the present study we examined the ability of flumazenil (Ro15-1788), a benzodiazepine receptor antagonist, to reverse neuronal and behavioral manifestations of ethanol tolerance and dependence. A single injection of flumazenil (10 mg/kg, 14 hr before withdrawal) to mice administered a liquid diet containing ethanol for 10 days, reduced seizure severity during withdrawal from ethanol. Acute tolerance to ethanol-induced hypothermia was not sensitive to flumazenil treatment, but tolerance and diazepam-induced cross-tolerance to the ataxic effects of ethanol were reversed by a single injection of flumazenil given 2 to 26 hr before evaluation of tolerance. At a biochemical level, the ability of benzodiazepine inverse agonists (e.g., Ro15-4513) to reduce the activity of gamma-aminobutyric acid (GABA) receptor-operated chloride channels may represent a neuronal manifestation of ethanol dependence (Buck and Harris, 1990). Flumazenil treatment of ethanol-dependent mice 14 hr before isolation of brain membrane vesicles partially reversed the augmentation of Ro15-4513 inhibition of muscimol-stimulated 36Cl- uptake in vitro. These results demonstrate that brief occupation of benzodiazepine receptors by an antagonist may reset the cellular mechanisms responsible for the development of ethanol tolerance and dependence, and support the hypothesis that increased sensitivity to benzodiazepine inverse agonists is involved in the development of ethanol dependence.

Alcoholism↗
PubMed1990

Anion channels activated by adrenaline in cardiac myocytes.

In heart cells, the catecholamine-activated cyclic AMP system regulates calcium and potassium channels. We report here a novel class of chloride channels that can be activated by adrenaline in mammalian ventricular cells. Like the agonist-activated Cl- channel currents of airway and colonic epithelial cells, the cardiac Cl(-)-channel current shows outward rectification. But the unit conductance of cardiac Cl- channels is smaller than that of epithelial Cl- channels. The cardiac Cl- channel is functionally voltage-independent, in contrast to the Cl- channel in colonic epithelial cells. This channel could be responsible for the beta-catecholamine-induced increase in cardiac membrane conductance that has been attributed to activation of a Cl- current. Thus, sympathetic control of cardiac electrical activity involves not only the voltage-dependent, excitation-related cation channels, but also anion channels that generate a steady current.

Animals↗
PubMed1997

The anxiolytic-like effects of the neurosteroid allopregnanolone: interactions with GABA(A) receptors.

The neurosteroid 3alpha-hydroxy-5alpha-pregnan-20-one (allopregnanolone) was administered systemically to rats which were tested in the Geller-Seifter conflict paradigm, an established animal model of anxiety. Allopregnanolone was found to produce significant anxiolytic-like effects at a dose of 8 mg/kg. When three ligands that function at different sites on the gamma-aminobutyric acid/benzodiazepine receptor-chloride ionophore complex (GABA(A) receptors) were examined in conjunction with allopregnanolone, the anti-conflict effects of allopregnanolone were effectively reversed only by the benzodiazepine receptor inverse agonist RO15-4513 (ethyl-8-azido-5,6-dihydro-5-methyl-6-oxo-4H-imidazo [1,5-alpha]-[1,4]benzodiazepine-3-carboxylate). Since this inverse agonist has been reported to inhibit the GABA(A)-activated chloride flux in neuronal membranes, it is likely that the stimulation of the chloride channel in GABA(A) receptors is an important component of the effects of allopregnanolone. In contrast, the benzodiazepine receptor antagonist flumazenil (ethyl-8-fluoro-5,6-dihydro-5-methyl-6-oxo-4H-imidazo [1,5-alpha]-[1,4]benzodiazepine-3-carboxylate) did not block the anxiolytic-like actions of allopregnanolone, indicating that allopregnanolone does not bind at the benzodiazepine site directly. Isopropylbicyclophosphate, which binds at the picrotoxinin site on the GABA(A) receptors and blocks the behavioral actions of ethanol, also dose-dependently reversed the anti-conflict effect of this neurosteroid. The results suggest that allopregnanolone may be working either at a site specific for the benzodiazepine receptor inverse agonist RO15-4513 or at the picrotoxinin site to produce its potent anxiolytic-like behavioral effects.

Affinity Labels↗