6-Hydroxydopamine induced impairment of Pavlovian conditioning in the rabbit.
This study employed bilateral, intraventricular injections of 6-hydroxydopamine (6-HDA) to examine the effects of monoamine depletion on Pavlovian conditioning of the rabbit's nictitating membrane response. 6-HDA produced dose-dependent and highly correlated decreases in the rate of acquisition of conditioned responses and in the telencephalic content of 5-HT, DA, and NE. At the highest dose of 6-HDA (1340 micrograms), 5-HT, DA, and NE were reduced by 42, 48, and 89%, respectively, and the number of trials required to achieve criterion acquisition was increased by 123%. Control experiments established that the highest dose of 6-HDA: 1) had no effect on the unconditioned nictitating membrane reflex; 2) had no effect on the threshold of the conditioned stimulus for eliciting conditioned responses; and 3) produced only a small, less than 5%, decrease in nonassociative responding. It was concluded that decreases in 5-HT, DA, and NE can impair associative learning without altering sensory or motor function.
Winsky
L
L
Section on Histopharmacology, National Institute of Mental Health, Bethesda, Maryland 20892.
Harvey
J A
JA
D000818:Animals; D003214:Conditioning, Classical / Q000187:drug effects*; D004298:Dopamine / Q000378:metabolism; D005260:Female; D008297:Male; D009638:Norepinephrine / Q000378:metabolism; D016627:Oxidopamine / Q000494:pharmacology*; D011817:Rabbits; D012701:Serotonin / Q000378:metabolism; D013687:Telencephalon / Q000187:drug effects / Q000378:metabolism
D012701:Serotonin; D016627:Oxidopamine; D004298:Dopamine; D009638:Norepinephrine