title: The local anesthetic effect of cyproheptadine on mammalian nerve fibres.
abstract: The local anesthetic effect of cyproheptadine on nerve fibres in the rabbit's cervical vagus and sciatic nerve was studied by the single sucrose-gap technique. Local anesthetics such as procaine and tetracaine, and an antihistaminic with local anesthetic activity, diphenhydramine, were studied for comparison. Increasing concentrations of cypropheptadine, starting from 5 x 10(-5) M, produced a dose-related fall in the amplitude of the compound action potential of the vagus nerve without significant change in the resting membrane potential. A complete reversibility of the local anesthetic effect was difficult or impossible to obtain when doses greater than 1 x 10(-4) M were used. Cyproheptadine was more potent than procaine and diphenhydramine, and less potent than tetracaine in producing nerve conduction block. Frequency-dependent block was observed with cyproheptadine and the other agents at frequencies that can be considered low (1--5 Hz). Myelinated fibres of the sciatic nerves were also blocked by cyproheptadine within the same range of concentrations (1 x 10(-4) to 1 x 10(-3) M). Our results provide an additional explanation for the mechanism underlying the actions of cyproheptadine as an antiarrhythmic and an antipruritic agent.
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000779:Anesthetics, Local; D000818:Animals; D003533:Cyproheptadine / Q000494:pharmacology*; D004155:Diphenhydramine / Q000494:pharmacology; D004558:Electric Stimulation; D066298:In Vitro Techniques; D009412:Nerve Fibers / Q000187:drug effects*; D011817:Rabbits
chemical_list: D000779:Anesthetics, Local; D003533:Cyproheptadine; D004155:Diphenhydramine