The role of a noradrenergic system in the antinociceptive effects of 4-aminopyridine in the rat.

Antinociceptive effects of physostigmine and 4-aminopyridine after i.p. administration were studied in rats according to the Randall-Selitto nociception method. The antinociceptive action of physostigmine was not significantly influenced by atropine, naloxone or alpha-methyl-p-tyrosine. The antinociceptive action of 4-aminopyridine was also unaffected by simultaneous administration of atropine, naloxone or pretreatment by DL-p-chlorophenylalanine. However, 4-aminopyridine was without antinociceptive effect in rats pretreated with alpha-methyl-p-tyrosine. It is suggested that the antinociceptive action of 4-aminopyridine is mediated by a noradrenergic system.