GABA-A and GABA-B receptors in the cuneate nucleus of the rat in vivo.
Electric stimulation of the rat forepaw evokes a negative potential (N-wave) at the ipsilateral cuneate nucleus. The responses of the N-wave to microiontophoretically applied GABA agonists and antagonists have been studied. Applications of GABA-A agonists (3-amino-propanesulfonic acid and muscimol) reduce the amplitude of the N-wave. This effect decreases during prolonged application, suggesting a desensitization of GABA-A receptors. In addition the effect of muscimol is reduced by (-)-bicuculline methiodide. Baclofen (a GABA-B agonist) also depresses the N-wave but its action lasts longer, is less reversible, shows no desensitization and is not blocked by (-)-bicuculline methiodide. The different responses of the N-wave to GABA-A and GABA-B agonists are compatible with the existence of different types of functional receptors for them in the cuneate nucleus of the rat. The receptors activated by muscimol (GABA-A) are clearly not the same as the ones activated by baclofen (conceivably GABA-B).
D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D004558:Electric Stimulation; D005071:Evoked Potentials; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology*; D009118:Muscimol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011963:Receptors, GABA-A / Q000187:drug effects*; D013654:Taurine / Q000031:analogs & derivatives / Q000494:pharmacology
D011963:Receptors, GABA-A; D013654:Taurine; D009118:Muscimol; C001355:tramiprosate; D001418:Baclofen