The gamma-aminobutyric acid-mimetic action of omega-aminocaprylic acid in rat cortex.

The 8-carbon chain analogue of gamma-aminobutyric acid (GABA), omega-aminocaprylic acid (omega-AC), was administered to single cortical neurones of rat by microiontophoresis and its effect on cell firing compared to the effect elicited by GABA. The spontaneous and glutamate-elicited firing rates of all cells examined were decreased by omega-AC, the molecule having an apparent potency approximately one-fifth that of GABA. Inhibitions induced by omega-AC were antagonized by bicuculline and enhanced by flurazepam. These data favour the view that extending chain length per se of the GABA molecule decreases the inhibitory potency of postsynaptic GABA receptor agonists. The results do not support the view that such structural changes alter the mode of action of GABA analogues, from inhibition to excitation, as has been suggested previously.