title: Synaptic facilitatory and depressant actions of 3,4-diaminopyridine: correlation with anticurare properties.
abstract: This study aimed to define the complete concentration-effect relationship for anticurare effects of 3,4-diaminopyridine (3,4-DAP) in the isolated sympathetic ganglion of the bullfrog. Synaptic transmission was monitored by extracellular and intracellular recordings of the postganglionic response to preganglionic stimulation. A previous study showed that in the bullfrog sympathetic ganglion 3,4-DAP caused stimulus-bound repetitive postganglionic responses (SBR) to each single preganglionic stimulus. The concentration-effect relationship for 3,4-DAP-induced SBR was bell-shaped, and the descending limb of the curve reflected progressive suppression of SBR while normal synaptic transmission was maintained. In the present study a detailed concentration-effect analysis of 3,4-DAP's anticurare action also resulted in a bell-shaped curve nearly congruent with that for SBR. SBR and anticurare effects of 3,4-DAP therefore occupy a common concentration-effect domain, and this suggests that a common mechanism (increased transmitter release) may account for both effects.
mesh_terms: D015761:4-Aminopyridine; D000077770:Amifampridine; D000631:Aminopyridines / Q000494:pharmacology*; D000818:Animals; D003472:Curare / Q000037:antagonists & inhibitors*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005728:Ganglia, Sympathetic / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D011892:Rana catesbeiana; D013569:Synapses / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects; D014403:Tubocurarine / Q000494:pharmacology
chemical_list: D000631:Aminopyridines; D003472:Curare; D015761:4-Aminopyridine; D000077770:Amifampridine; D014403:Tubocurarine