Effects of amiridin on ambulatory activity and the discrete shuttle avoidance response in mice

Abstract

Behavioral effects of amiridin, [9-amino-2,3,5,6,7,8-hexahydro-1H-cyclopenta (b)-quinoline monohydrate hydrochloride] were investigated by observing ambulatory activity and the discrete shuttle avoidance response in mice. In addition, the in vivo effects of 4-amino-pyridine and physostigmine, which have inhibitory effects similar to those of amiridin on acetylcholine esterase in vitro, were compared with those of amiridin. Single doses of amiridin (0.3-10 mg/kg, s.c.) or 4-aminopyridine (0.3-3 mg/kg, s.c.) failed to produce marked changes in ambulatory activity, nor did these drugs exhibit any antagonistic effect on the ambulation-increasing effect of scopolamine (0.5 mg/kg, s.c.). However, single doses of physostigmine (0.03-0.1 mg/kg, s.c.) suppressed the ambulatory activity and antagonized with scopolamine. Amiridin (1-3 mg/kg, s.c. and 0.3-1 mg/kg, p.o.) and 4-aminopyridine (1-3 mg/kg, s.c.) administered to mice immediately before the training start of the discrete shuttle avoidance response facilitated the acquisition process. Furthermore, amiridin, but not 4-aminopyridine, elicited a good retention of the avoidance response after 24 hr. Although amiridin and 4-aminopyridine facilitated acquisition of the avoidance response, they failed to affect an avoidance response which had been established by sufficient previous training. On the other hand, physostigmine (0.1 mg/kg, s.c.) not only retarded acquisition of the avoidance response, but also suppressed established avoidance responses. The present results suggest that amiridin facilitates both acquisition and memory processes of mice in the discrete shuttle avoidance situation without eliciting a marked change in general activity level.