Effects of GABA-mimetic agents on the cat spinal cord.
Muscimol, ibotenic acid, isoguvacine, 4,5,6,7-tetrahydroisoxazolo [5,4-c]pyridin-3-ol (THIP) and gamma-aminobutyric acid (GABA) injected intravenously exerted the following dose-dependent effects on the lumbosacral spinal cord of spinal cats: 1. The excitability of primary afferents and the amplitude of dorsal root reflexes were enhanced; segmental monosynaptic ventral root reflexes and dorsal root potentials as well as the spontaneous gamma-fibre activity and, to a smaller extent, the excitability of motoneurons and polysynaptic reflexes, were depressed. 2. Muscimol was the most potent compound (0.3-1 mg/kg produced significant effects), followed by ibotenic acid (3-10 mg/kg), isoguvacine and THIP (10-30 mg/kg) and GABA (100 mg/kg). 3. Most effects were reversibly antagonized by bicuculline, but not by strychnine, indicating that they were due to a specific interaction with GABA-receptors. 4. These results suggest that the systemic injection of GABA-mimetic agents affects spinal cord activities by actions related to GABA-receptors located on primary afferent endings, intrinsic spinal neurons, and motoneurons.
D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D002415:Cats; D004347:Drug Interactions; D018756:GABA Antagonists; D005727:Ganglia, Spinal / Q000502:physiology; D007051:Ibotenic Acid / Q000494:pharmacology; D007539:Isonicotinic Acids / Q000494:pharmacology; D007555:Isoxazoles / Q000494:pharmacology; D008297:Male; D009118:Muscimol / Q000494:pharmacology; D009475:Neurons, Afferent / Q000502:physiology; D013116:Spinal Cord / Q000187:drug effects*; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D018756:GABA Antagonists; D007539:Isonicotinic Acids; D007555:Isoxazoles; D007051:Ibotenic Acid; D009118:Muscimol; D005680:gamma-Aminobutyric Acid; C015542:gaboxadol; D001640:Bicuculline; C015300:isoguvacine