The effects of (-)-
lobeline were assessed in two learning and memory tasks in which
nicotine-induced enhancement of performance has previously been demonstrated.
Lobeline (19 mumol/kg, IP) administered immediately after inhibitory (passive) avoidance training improved retention performance assessed 24 h later, as rats that received this dose of
lobeline took significantly longer to enter the
shock compartment on the test day than rats that had been treated with vehicle. Pretraining
lobeline treatment (1.9 mumol/kg, IP) significantly improved performance of rats with septal lesions in a spatial discrimination water maze, a finding confirmed when rats were retrained using new spatial locations and vehicle and
lobeline treatments were reversed in a crossover design. The effective dose of
lobeline in the inhibitory avoidance task was about 10-fold higher than that generally reported for
nicotine, and direct comparison of the suppression of locomotor activity shortly after administration of
nicotine or
lobeline also revealed a 10-fold greater potency for
nicotine. In contrast, no difference was found between the effective dose of
lobeline in the current study and that we previously found with
nicotine in the water maze. These findings suggest that
lobeline's effects on the performance of learning and memory tasks may be similar to those of
nicotine. Coupled with previous reports that
lobeline does not produce the
nicotine cue in
drug discrimination experiments, this study also suggests that
nicotinic receptors involved in the modulation of memory processes may be distinct from those involved in producing the
nicotine cue.