5,7-DHT-INDUCED LESIONS OF THE NUCLEUS BASALIS OR FRONTAL-CORTEX DO NOT BLOCK PASSIVE-AVOIDANCE RETENTION IMPAIRMENTS PRODUCED BY P-CHLOROAMPHETAMINE IN RATS

The effects of serotonergic lesions of the nucleus basalis of Meynert (nbM) or regions within the frontal cortex (FCTX) induced with 5,7-dih ydroxytryptamine were examined to determine whether such damage would block the amnesia-producing effect of pretraining (30 min) p-chloroamp hetamine (PCA; 2.5 mg/kg) in rats trained on passive avoidance. Result s indicated that, irrespective of their lesion condition, all groups t reated with PCA exhibited 72-h retention impairments. Serotonergic les ions of the nbM or FCTX alone did not affect retention performance des pite producing extensive depletions of serotonin (34.8%-84.7%) and 5-h ydroxyindoleacetic acid (59.0%-86.0%). Neither lesion procedure, nor t he administration of PCA, had an effect on activity levels of choliner gic markers choline acetyltransferase and acetylcholinesterase within the frontal cortex. These data demonstrate that the memory-impairing e ffects of PCA are not (1) dependent on the existence of releasable poo ls of serotonin in the nbM or FCTX, (2) mediated by stimulation of ser otonergic receptors in the nbM or FCTX, or (3) related to disruption o f cholinergic activity within the frontal cortex. These data also reve al that serotonergic lesions to the nbM or FCTX by themselves do not p roduce impairments in retention on passive avoidance.