title: Studies on convulsants in the isolated frog spinal cord. II. Effects on root potentials.
abstract: 1. In the isolated frog spinal cord picrotoxin, bicuculline, and strychnine were evaluated for their effects on synaptically induced root potentials recorded by the sucrose gap technique. 2. Picrotoxin (greater than 10- minus 4 M) completely blocked the dorsal root potential (DRP) elicited by stimulating the ventral root of the same segment (VR-DRP). Although picrotoxin antagonized the DRP elicited by stimulation of either an adjacent dorsal root (DR-DRP) or the lateral column (LC-DRP), a slower component to these  potentials appeared and increased in size as the concentration of picrotoxin was increased. Thus picrotoxin brings out a later, picrotoxin resistant component to the DR-DRP and LC-DRP. 3. Strychnine (10- minus 8-10- minus 5 M) reduced and abolished the VR-DRP without prolongation and progressively increased and prolonged the DR-DRP (and LC-DRP) and the DR-VRP. Strychnine in higher concentrations (greater than 10- minus 4 M) also reduced the amplitude and prolonged the duration of the compound action potential of afferent fibres. 4. These results combined with those presented in the preceding paper (Barker, Nicoll & Padjen, 1975) suggest that (1) a GABA-like transmitter mediates the final step in the DR-DRP and LC-DRP pathways and that (2) either taurine or beta-alanine may mediate the last step in the VR-DRP pathway.
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000409:Alanine / Q000502:physiology; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D003292:Convulsants / Q000494:pharmacology; D004558:Electric Stimulation; D066298:In Vitro Techniques; D009475:Neurons, Afferent / Q000187:drug effects; D010477:Perfusion; D010852:Picrotoxin / Q000494:pharmacology; D011894:Rana pipiens; D013126:Spinal Nerve Roots / Q000187:drug effects*; D013331:Strychnine / Q000494:pharmacology; D013569:Synapses / Q000187:drug effects; D009435:Synaptic Transmission; D013654:Taurine / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000502:physiology
chemical_list: D000409:Alanine; D001640:Bicuculline; D003292:Convulsants; D010852:Picrotoxin; D013331:Strychnine; D013654:Taurine; D005680:gamma-Aminobutyric Acid