Effects of the conformationally restricted GABA analogues, cis- and trans-4-aminocrotonic acid, on GABA neurotransmission in primary neuronal cultures.
The effects of the GABA analogues, cis- and trans-4-aminocrotonic acid (ACA) on GABA(A) receptor function and GABA uptake, together with the presence of p-1 subunit mRNA and putative GABAc receptors, were studied in primary cultures of neocortical neurons and cerebellar granule cells. Both isomers induced a Cl- influx, which was inhibited by bicuculline, t-butylbicyclophosphorothionate (TBPS), picrotoxinin (PTX), and gamma-hexachlorocyclohexane (gamma-HCH or lindane). [3H]-flunitrazepam binding was also increased by both isomers and this increase was inhibited by bicuculline. In neocortical neurons, the transisomer completely inhibited the [3H]GABA uptake, whereas the cis-isomer produced only a 25% inhibition at the highest concentration used. The possible presence of GABAc receptors was investigated only in neocortical cultures by using RT-PCR in order to detect the presence of the mRNA encoding the p-1 subunit which assembles to form homooligomeric Cl-channels. The results presented here show that p-1 subunits, and thus GABAc receptors, may represent a very minor population of GABA receptors in these neuronal preparations. We conclude that both GABA analogues may act as agonists at the GABA(A) receptors, although with very different potencies.
Vale
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Department of Neurochemistry, Institut d'Investigacions Biomèdiques de Barcelona, CSIC (IDIBAPS), Spain.
Vilaró
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MT
Rodríguez-Farré
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Suñol
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D000818:Animals; D001665:Binding Sites; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000187:drug effects*; D002713:Chlorine / Q000378:metabolism; D003437:Crotonates / Q000737:chemistry / Q000494:pharmacology*; D005445:Flunitrazepam / Q000378:metabolism; D018757:GABA Modulators / Q000378:metabolism; D019579:Neocortex / Q000166:cytology / Q000187:drug effects*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011963:Receptors, GABA-A / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D017661:Receptors, Presynaptic / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013237:Stereoisomerism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D003437:Crotonates; D018757:GABA Modulators; D012333:RNA, Messenger; D011963:Receptors, GABA-A; D017661:Receptors, Presynaptic; C055331:4-aminocrotonic acid; D002713:Chlorine; D005680:gamma-Aminobutyric Acid; D005445:Flunitrazepam