piperidines and 5-(4-piperidyl)isoxazol-3-ol

The GABA(A) receptor system is implicated in a number of neurological diseases, making GABA(A) receptor ligands interesting as potential therapeutic agents. Only a few different classes of structures are currently known as ligands for the GABA recognition site on the GABA(A) receptor complex, reflecting the very strict structural requirements for GABA(A) receptor recognition and activation. Within the series of compounds showing agonist activity at the GABA(A) receptor site that have been developed, most of the ligands are structurally derived from the GABA(A) agonists muscimol, THIP or isoguvacine. Using recombinant GABA(A) receptors, functional selectivity has been shown for a number of compounds such as the GABA(A)agonists imidazole-4-acetic acid and THIP, showing highly subunit-dependent potency and maximal response. In the light of the interest in partial GABA(A) receptor agonists as potential therapeutics, structure-activity studies of a number of analogues of 4-PIOL, a low-efficacy partial GABA(A) agonist, have been performed. In this connection, a series of GABA(A) ligands has been developed showing pharmacological profiles from moderately potent low-efficacy partial GABA(A) agonist activity to potent and selective antagonist effect. Only little information about direct acting GABA(A) receptor agonists in clinical studies is available. Results from clinical studies on the effect of the GABA(A) agonist THIP on human sleep pattern shows that the functional consequences of a direct acting agonist are different from those seen after administration of GABA(A) receptor modulators.

Topics: Animals; Central Nervous System Diseases; GABA Agents; GABA Agonists; GABA Antagonists; Humans; Isonicotinic Acids; Isoxazoles; Ligands; Muscimol; Piperidines; Protein Subunits; Receptors, GABA-A

Tonic GABA currents mediated by high-affinity extrasynaptic GABAA receptors, are increasingly recognized as important regulators of cell and neuronal network excitability. Dysfunctional GABAA receptor signaling that results in modified tonic GABA currents is associated with a number of neurological disorders. Consequently, developing compounds to selectively modulate the activity of extrasynaptic GABAA receptors underlying tonic inhibition is likely to prove therapeutically useful. Here, we examine the GABAA receptor subtype selectivity of the weak partial agonist, 5-(4-piperidyl)isoxazol-3-ol (4-PIOL), as a potential mechanism for modulating extrasynaptic GABAA receptor-mediated tonic currents. By using recombinant GABAA receptors expressed in HEK293 cells, and native GABAA receptors of cerebellar granule cells, hippocampal neurons, and thalamic relay neurons, 4-PIOL evidently displayed differential agonist and antagonist-type profiles, depending on the extrasynaptic GABAA receptor isoforms targeted. For neurons, this resulted in differential modulation of GABA tonic currents, depending on the cell type studied, their respective GABAA receptor subunit compositions, and critically, on the ambient GABA levels. Unexpectedly, 4-PIOL revealed a significant population of relatively low-affinity γ2 subunit-containing GABAA receptors in the thalamus, which can contribute to tonic inhibition under specific conditions when GABA levels are raised. Together, these data indicate that partial agonists, such as 4-PIOL, may be useful for modulating GABAA receptor-mediated tonic currents, but the direction and extent of this modulation is strongly dependent on relative expression levels of different extrasynaptic GABAA receptor subtypes, and on the ambient GABA levels.. A background level of inhibition (tonic) is important in the brain for controlling neuronal excitability. Increased levels of tonic inhibition are associated with some neurological disorders but there are no specific ligands capable of selectively reducing tonic inhibition. Here we explore the use of a GABA partial agonist as a selective chemical tool in three different brain regions. We discover that the activity of a partial agonist is heavily dependent upon the GABAA receptor subunit composition underpinning tonic inhibition, and on the ambient levels of GABA in the brain.

Topics: Animals; Animals, Newborn; Brain; Cells, Cultured; Dose-Response Relationship, Drug; Excitatory Amino Acid Agents; GABA Agents; gamma-Aminobutyric Acid; Humans; In Vitro Techniques; Inhibitory Postsynaptic Potentials; Isoxazoles; Membrane Potentials; Neural Inhibition; Neurons; Patch-Clamp Techniques; Piperidines; Protein Subunits; Rats; Rats, Sprague-Dawley; Receptors, GABA-A

GABAA receptors mediate two different types of inhibitory currents: phasic inhibitory currents when rapid and brief presynaptic GABA release activates postsynaptic GABAA receptors and tonic inhibitory currents generated by low extrasynaptic GABA levels, persistently activating extrasynaptic GABAA receptors. The two inhibitory current types are mediated by different subpopulations of GABAA receptors with diverse pharmacological profiles. Selective antagonism of tonic currents is of special interest as excessive tonic inhibition post-stroke has severe pathological consequences. Here we demonstrate that phasic and tonic GABAA receptor currents can be selectively inhibited by the antagonists SR 95531 and the 4-PIOL derivative, 4-(3,3-diphenylpropyl)-5-(4-piperidyl)-3-isoxazolol hydrobromide (DPP-4-PIOL), respectively. In dentate gyrus granule cells, SR 95531 was found approximately 4 times as potent inhibiting phasic currents compared to tonic currents (IC50 values: 101 vs. 427 nM). Conversely, DPP-4-PIOL was estimated to be more than 20 times as potent inhibiting tonic current compared to phasic current (IC50 values: 0.87 vs. 21.3 nM). Consequently, we were able to impose a pronounced reduction in tonic GABA mediated current (>70 %) by concentrations of DPP-4-PIOL, at which no significant effect on the phasic current was seen. Our findings demonstrate that selective inhibition of GABA mediated tonic current is possible, when targeting a subpopulation of GABAA receptors located extrasynaptically using the antagonist, DPP-4-PIOL.

Topics: Animals; Cytoplasmic Granules; Dentate Gyrus; GABA-A Receptor Antagonists; gamma-Aminobutyric Acid; Isoxazoles; Mice; Neurons; Piperidines; Receptors, GABA-A

Protein-protein interfaces provide an important class of drug targets currently receiving increased attention. The typical design strategy to inhibit protein-protein interactions usually involves large molecules such as peptides and macrocycles. One exception is tranexamic acid (TXA), which, as a lysine mimetic, inhibits binding of plasminogen to fibrin. However, the daily dose of TXA is high due to its modest potency and pharmacokinetic properties. In this study, we report a computational approach, where the focus was on finding electrostatic potential similarities to TXA. Coupling this computational technique with a high-quality low-throughput screen identified 5-(4-piperidyl)-3-isoxazolol (4-PIOL) as a potent plasminogen binding inhibitor with the potential for the treatment of various bleeding disorders. Remarkably, 4-PIOL was found to be more than four times as potent as the drug TXA.

Topics: Antifibrinolytic Agents; Computational Biology; Drug Evaluation, Preclinical; Fibrinolysis; Humans; Isoxazoles; Models, Molecular; Piperidines; Plasminogen; Protein Binding; Static Electricity; Tranexamic Acid

Drugs used to treat various disorders target GABA A receptors. To develop alpha subunit selective compounds, we synthesized 5-(4-piperidyl)-3-isoxazolol (4-PIOL) derivatives. The 3-isoxazolol moiety was substituted by 1,3,5-oxadiazol-2-one, 1,3,5-oxadiazol-2-thione, and substituted 1,2,4-triazol-3-ol heterocycles with modifications to the basic piperidine substituent as well as substituents without basic nitrogen. Compounds were screened by [(3)H]muscimol binding and in patch-clamp experiments with heterologously expressed GABA A alpha ibeta 3gamma 2 receptors (i = 1-6). The effects of 5-aminomethyl-3 H-[1,3,4]oxadiazol-2-one 5d were comparable to GABA for all alpha subunit isoforms. 5-piperidin-4-yl-3 H-[1,3,4]oxadiazol-2-one 5a and 5-piperidin-4-yl-3 H-[1,3,4]oxadiazol-2-thione 6a were weak agonists at alpha 2-, alpha 3-, and alpha 5-containing receptors. When coapplied with GABA, they were antagonistic in alpha 2-, alpha 4-, and alpha 6-containing receptors and potentiated alpha 3-containing receptors. 6a protected GABA binding site cysteine-substitution mutants alpha 1F64C and alpha 1S68C from reacting with methanethiosulfonate-ethylsulfonate. 6a specifically covalently modified the alpha 1R66C thiol, in the GABA binding site, through its oxadiazolethione sulfur. These results demonstrate the feasibility of synthesizing alpha subtype selective GABA mimetic drugs.

Topics: Animals; Binding Sites; Brain; Cell Line; Electrophysiology; Female; GABA-A Receptor Agonists; gamma-Aminobutyric Acid; Humans; Isoxazoles; Models, Molecular; Molecular Structure; Muscimol; Mutation; Oocytes; Patch-Clamp Techniques; Piperidines; Protein Subunits; Rats; Receptors, GABA-A; Structure-Activity Relationship; Xenopus laevis

The GABA(A) receptor system is implicated in a number of central nervous system (CNS) disorders, making GABA(A) receptor ligands interesting as potential therapeutic agents. Only a few different classes of structures are currently known as ligands for the GABA recognition site on the hetero-pentameric GABA(A) receptor complex, reflecting the very strict structural requirements for GABA(A) receptor recognition and activation. A large number of the compounds showing agonist activity at the GABA(A) receptor site are structurally derived from the GABA(A) agonists muscimol, THIP (Gaboxadol), or isoguvacine, which we developed at the initial stage of the project. Using recombinant GABA(A) receptors, functional selectivity has been shown for a number of compounds, including THIP, showing subunit-dependent potency and maximal response. The pharmacological and clinical activities of THIP probably reflect its potent effects at extrasynaptic GABA(A) receptors insensitive to benzodiazepines and containing alpha(4)beta(3)delta subunits. The results of ongoing clinical studies on the effect of the partial GABA(A) agonist THIP on human sleep pattern show that the functional consequences of a directly acting agonist are distinctly different from those seen after administration of GABA(A) receptor modulators, such as benzodiazepines. In the light of the interest in partial GABA(A) receptor agonists as potential therapeutics, structure-activity studies of a number of analogues of 4-PIOL, a low-efficacy partial GABA(A) agonist derived from THIP, have been performed. In this connection, a series of GABA(A) ligands has been developed showing pharmacological profiles ranging from low-efficacy partial GABA(A) agonist activity to selective antagonist effect.

Topics: Analgesics, Non-Narcotic; Anxiety; GABA Agonists; GABA Antagonists; GABA-A Receptor Agonists; GABA-A Receptor Antagonists; Humans; Hypnotics and Sedatives; Isoxazoles; Piperidines; Sleep Wake Disorders

A series of novel 5-(4-piperidyl)-3-isoxazolol (4-PIOL) analogues where the 4-position of the 3-isoxazolol ring was substituted with groups of different size, flexibility, and lipophilicity have been characterised. Their activity as agonists and/or antagonists on human alpha(1)beta(2)gamma(2S) GABA(A) receptors expressed in Xenopus oocytes was studied using two-electrode voltage clamp electrophysiology. Methyl- and ethyl-substituted 4-PIOL analogues were characterised as partial agonists since weak agonist responses could be potentiated with lorazepam and inhibited by the competitive antagonist 2-(3-carboxypropyl)-3-amino-6-methoxyphenyl-pyradizinum bromide (SR95531). All larger substituents in the 4-position of the 3-isoxazolol ring of 4-PIOL converted the compounds into pure competitive antagonists. Additionally, for GABA, 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP), piperidine-4-sulphonic acid (P4S), and 5-(4-piperidyl)-3-isothiazolol (thio-4-PIOL), a negative linear correlation was found between the agonist efficacy of the compound and the ability of lorazepam to potentiate EC(95) responses. Furthermore, a positive linear correlation between the lipophilicity of the substituents in the 4-position of the 3-isoxazolol ring of 4-PIOL and the antagonist affinity was found. These data suggest that the GABA(A) receptor contains a hydrophobic binding pocket at the GABA recognition site and that the binding of the 4-PIOL analogues is largely determined by the transfer from the aqueous phase to the hydrophobic pocket.

Topics: Animals; Dose-Response Relationship, Drug; Female; GABA-A Receptor Agonists; Humans; Hydrophobic and Hydrophilic Interactions; Isoxazoles; Piperidines; Receptors, GABA-A; Xenopus laevis

In order to study the correlation of the thermodynamic driving forces of binding with the efficacies of displacing ligands, the specific binding of [3H]SR 95531 [2-(3-carboxypropyl)3-amino-6-p-methoxyphenylpyridazinium bromide], a GABA(A) receptor antagonist, was studied in cell lines stably expressing human alpha(1)beta(3)gamma(2) and alpha(2)beta(3)gamma(2) GABA(A) receptors. Displacing potencies for the agonists with different efficacies (muscimol, 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP) and piperidine-4-sulfonic acid) and for antagonists (SR 95531 and 5-(4-piperidyl)isothiazol-3-ol) were determined at 0 degrees C, 20 degrees C and 37 degrees C. Displacing potencies were temperature-nearly independent for alpha(1)beta(3)gamma(2) receptors. At alpha(2)beta(3)gamma(2), receptor binding of the antagonists was exothermic, endothermic for the agonists THIP and piperidine-4-sulfonic acid and isothermic for muscimol. The free energy increments of displacement for the binding of the antagonist [3H]SR 95531 versus the agonist [3H]muscimol approach saturation as a function of the efficacies of the displacers only for alpha(1)beta(3)gamma(2) receptors. This suggests that, for binding to alpha(1)beta(3)gamma(2) GABA(A) receptors, displacement is an efficacy-dependent interaction predominantly driven by entropic increases.

Topics: Animals; Binding, Competitive; Dose-Response Relationship, Drug; Entropy; GABA Agonists; GABA Antagonists; Humans; Isoxazoles; L Cells; Membranes; Mice; Muscimol; Piperidines; Pyridazines; Receptors, GABA-A; Recombinant Proteins; Temperature; Tritium

Based on an unexpected high maximum response to piperidine-4-sulphonic acid (P4S) at human alpha1alpha6beta2gamma2 GABA(A) receptors expressed in Xenopus oocytes attempts to correlate this finding with the pharmacological profile of P4S and other GABA(A) receptor ligands in neuronal cultures from rat cerebellar granule cells and rat cerebral cortex were carried out. GABA and isoguvacine acted as full and piperidine-4-sulphonic acid (P4S) as partial agonists, respectively, at alpha1beta2gamma2, alpha6beta2gamma2 and alpha1alpha6beta2gamma2 GABA receptors expressed in Xenopus oocytes with differences in potency. Whole-cell patch-clamp recordings were used to investigate the pharmacological profile of the partial GABA(A) receptor agonists 4,5,6,7-tetrahydroisoxazolo-(5,4-c)pyridin-3-ol (THIP), P4S, 5-(4-piperidyl)isoxazol-3-ol (4-PIOL), and 3-(4-piperidyl)isoxazol-5-ol (iso-4-PIOL), and the competitive GABA(A) receptor antagonists Bicuculline Methbromide (BMB) and 2-(3-carboxypropyl)-3-amino-6-methoxyphenyl-pyridazinium bromide (SR95531) on cerebral cortical and cerebellar granule neurons. In agreement with findings in oocytes, GABA, isoguvacine and P4S showed similar pharmacological profiles in cultured cortical and cerebellar neurones, which are known to express mainly alpha1, alpha2, alpha3, and alpha5 containing receptors and alpha1, alpha6 and alpha1alpha6 containing receptors, respectively. 4-PIOL and iso-4-PIOL, which at GABA(A) receptors expressed in oocytes were weak antagonists, showed cell type dependent potency as inhibitors of GABA mediated responses. Thus, 4-PIOL was slightly more potent at cortical neurones than at granule neurones and iso-4-PIOL was more potent in inhibiting isoguvacine-evoked currents at cortical than at granule neurons. Furthermore the maximum response to 4-PIOL corresponded to that of a partial agonist, whereas that of iso-4-PIOL gave a maximum response close to zero. It is concluded that the pharmacological profile of partial agonists is highly dependent on the receptor composition, and that small structural changes of a ligand can alter the selectivity towards different subunit compositions. Moreover, this study shows that pharmacological actions determined in oocytes are generally in agreement with data obtained from cultured neurons.

Topics: Animals; Bicuculline; Cells, Cultured; Cerebellum; Cerebral Cortex; Electrophysiology; GABA Agonists; GABA-A Receptor Agonists; Isonicotinic Acids; Isoxazoles; Mice; Neurons; Oocytes; Patch-Clamp Techniques; Piperidines; Pyridazines; Receptors, GABA-A; Xenopus laevis

Eight gamma-aminobutyric acid (GABA) mimetics were tested on their ability to differentiate native GABA(A) receptor subtypes present in various rat brain regions. In rat brain cryostat sections, little regional variations by the agonistic actions of muscimol, thiomuscimol, 4,5,6,7-tetrahydroisoazolo(5,4-c)pyridin-3-ol, piperidine-4-sulphonic acid, taurine and beta-alanine on [35S]t-butylbicyclophosphorothionate ([35S]TBPS) binding to GABA(A) receptor channels were found. They were very similar to those found for GABA itself and indicated no direct correlation with single subunit distributions for any of these compounds. Only the low-efficacy GABA mimetic 5-(4-piperidyl)isoxazol-3-ol (4-PIOL) acted like a weak partial agonist or antagonist depending on the brain area. As the cerebellar granule cell layer was relatively insensitive to both modes of action, we tested 4-PIOL in recombinant alpha1beta2gamma2 (widespread major subtype) and alpha6beta2gamma2 (cerebellar granule cell restricted) receptors where it had different effects on GABA-modulated [35S]TBPS binding and on electrophysiological responses. 4-PIOL may thus serve as a potential lead for receptor subtype selective compounds.

Topics: Animals; Brain; Bridged Bicyclo Compounds, Heterocyclic; Cell Line; GABA Agonists; Humans; Ionophores; Isoxazoles; Ligands; Male; Piperidines; Rats; Rats, Wistar; Receptors, GABA-A

Topics: Animals; Brain; Cells, Cultured; GABA Antagonists; Isoxazoles; Models, Molecular; Muscimol; Neurons; Patch-Clamp Techniques; Piperidines; Radioligand Assay; Rats; Receptors, GABA-A; Structure-Activity Relationship; Synaptic Membranes

gamma-Aminobutyric acidA (GABA(A)) gated chloride ion channels were expressed from human recombinant cDNA using the baculovirus/Sf-9 insect cell expression system. The electrophysiological effects in whole-cell currents of 5-(4-piperidyl) isoxazol-3-ol (4-PIOL), a GABA(A) receptor partial agonist, were investigated on GABA(A) receptor complexes of alpha1beta2gamma2S subunits as well as a slightly modified construct of alpha1(valine 121)beta2gamma2S subunits. Here we report that (1)4-PIOL induces an inward whole-cell current in a concentration-dependent manner in both alpha1(val 121)beta2gamma2S and alpha1(ile 121)beta2gamma2S receptor subunit combinations. (2) The 4-PIOL induced whole-cell currents were more pronounced in alpha1(val 121)beta2gamma2S than in alpha1(ile 121)beta2gamma2S receptor subunit combinations. (3) 4-PIOL inhibited GABA-induced responses on alpha1(ile 121)beta2gamma2S and alpha1(val 121)beta2gamma2S receptor combinations with similar potency.

Topics: Animals; Cell Line; GABA Agonists; gamma-Aminobutyric Acid; Humans; Isoxazoles; Kinetics; Macromolecular Substances; Membrane Potentials; Mutagenesis, Site-Directed; Patch-Clamp Techniques; Piperidines; Receptors, GABA-A; Recombinant Proteins; Spodoptera; Transfection; Valine

We have previously characterized 5-(4-piperidyl)isoxazol-3-ol (4-PIOL) as a non-desensitizing partial agonist at GABAA receptors and shown that the responses are mediated by short-duration channel openings consonant with single-ligand gated openings of the Cl- channels. We presently investigate whether responses of cultured rat hippocampal neurones to 4-PIOL are modulated by benzodiazepine (BDZ) and barbiturate receptor ligands. Whole-cell patch-clamp recordings of maximal responses to 1 mM 4-PIOL were comparable in size to responses evoked by 10 microM of the full GABAA agonist, isoguvacine. The BDZ receptor inverse agonist, DMCM (1 microM) reduced responses to isoguvacine (to 65.7 +/- 11.0%) and 4-PIOL (to 69.3 +/- 3.5%) to a similar extent. The BDZ agonist, midazolam (0.1 microM) potentiated responses to both agonists, and resulted in responses with an early peak with later fading. Potentiation of the peak response to 4-PIOL (to 163 +/- 14%) was significantly less than for isoguvacine (215 +/- 11%). Pentobarbital (50 microM) caused a very marked, but variable, potentiation of the peak response to 4-PIOL (to 484 +/- 93%), which was significantly greater than the potentiation of the peak response to isoguvacine (to 304 +/- 46%), and induced fading. This suggests that a relatively larger number of the 4-PIOL-induced channel openings can be transformed to longer duration openings by pentobarbital. In conclusion, responses to 4-PIOL and isoguvacine are modulated by BDZ and barbiturate ligands in a qualitatively similar manner, but with a number of quantitative differences which cannot be readily explained by the kinetic model of Macdonald and Twyman (1992). Investigation of these responses at the single-channel level could provide further insight into the operation of the GABAA receptor-ionophore complex.

Topics: Animals; Barbiturates; Benzodiazepines; Carbolines; Cells, Cultured; Convulsants; Electrophysiology; GABA Agonists; GABA Modulators; GABA-A Receptor Agonists; Hippocampus; Hypnotics and Sedatives; Isonicotinic Acids; Isoxazoles; Membrane Potentials; Midazolam; Neurons; Patch-Clamp Techniques; Pentobarbital; Piperidines; Rats

4-PIOL is a structural analog of GABA that has low efficacy at GABAA receptor CI- channels and activates a nondesensitizing CI- conductance in central neurons. We investigated the biophysical mechanisms of its low efficacy in embryonic olfactory bulb neurons, which express a limited number of GABAA receptor subunit transcripts. Spectral analysis of GABA- and 4-PIOL-induced current fluctuations evoked in whole-cell recordings showed that three components with mean durations of approximately 0.7, 5, and 50 msec adequately describe the kinetics of the responses induced by both ligands. The contribution of the longest-lasting component was approximately 60% in the spectra of GABA-evoked responses but < 3% in the spectra of 4-PIOL-evoked responses. This is interpreted as a low incidence of long-lasting bursts in 4-PIOL-evoked responses. No difference was evident between the average inferred unitary conductances for 4-PIOL- and GABA-induced channels. These results at the level of the whole cell were confirmed and extended in outside-out single channel recordings. Taken together, the results indicate that the mechanism responsible for the low efficacy of 4-PIOL is the inability to produce frequent bursts of long duration.

Topics: Animals; Chloride Channels; Female; GABA Agonists; GABA-A Receptor Agonists; gamma-Aminobutyric Acid; Ion Channel Gating; Isoxazoles; Kinetics; Neurons; Olfactory Bulb; Piperidines; Pregnancy; Rats; Rats, Sprague-Dawley

1. Whole-cell, patch-clamp recordings from cultured hippocampal neurones have been used to characterize the action of the GABAA ligand, 5-(4-piperidyl)isoxazol-3-ol (4-PIOL). The action of 4-PIOL was compared with that of the established GABAA agonist, isoguvacine. 2. With a symmetrical Cl- gradient across the membrane and a holding potential of -60mV, both isoguvacine and 4-PIOL evoked an inward current. The reversal potentials of the responses to both agents were identical (+8.8 mV, n = 4) and the current/voltage relationships showed outward-going rectification. 3. The response to 300 microM 4-PIOL was completely blocked by the GABAA antagonist, bicuculline methobromide (BMB, 10 microM). The pA2 of BMB was greater than 6.46. With 2 mM 4-PIOL about 15% of the response remained in the presence of 100 microM BMB. This may represent a non-specific component of the response to large concentrations of 4-PIOL. 4. 4-PIOL was about 200 times less potent as an agonist than isoguvacine. because of the rapid fade (desensitization) of isoguvacine-induced currents, the maximum response to this agonist was not determined. However, the response to 2 mM 4-PIOL was only a small fraction of that evoked by submaximal concentrations of isoguvacine. 5. Setting the response to 1 mM 4-PIOL as maximum, the EC50 for 4-PIOL was 91 microM (95% confidence limits:73-114 microM). 6. 4-PIOL antagonized the response to isoguvacine with a parallel shift to the right of the dose-response curve. The antagonist action of 4-PIOL was about 30 times weaker than that of BMB. When allowance was made for the intrinsic agonist action of 4-PIOL, the Ki was 116p microM (95% confidence limits: 102-130 microM). This was not significantly different from EC5, (P = 0.86; non-parametric Mann-Whitney test).7. It is concluded that 4-PIOL is a partial agonist at the GABAA receptor on cultured hippocampal neurones.

Topics: Animals; Bicuculline; Cells, Cultured; Female; Hippocampus; Isonicotinic Acids; Isoxazoles; Membrane Potentials; Neurons; Piperidines; Pregnancy; Rats; Receptors, GABA-A; Spinal Cord