Effects of d-lysergic acid diethylamide, d-2-bromolysergic acid diethylamide, dl-2,5-dimethoxy-4-methylamphetamine and d-amphetamine on classical conditioning of the rabbit nictitating membrane response
Harvey, J.A.; Gormezano, I.; Cool, V.A.
Journal of Pharmacology and Experimental Therapeutics 221(2): 289-294
1982
ISSN/ISBN: 0022-3565 PMID: 6122729 Document Number: 5241
Classical conditioning of the rabbit nictitating membrane response was accomplished by presenting tone and light conditioned stimuli for 800 ms before delivery of the unconditioned stimulus consisting of a 100-ms electric shock to the skin over the paraorbital region of the head. The rate of acquisition of conditioned responses to both tone and light conditioned stimuli was significantly increased by both d-LSD and dl-2,5-dimethoxy-4-methylamphetamine (DOM). d-Amphetamine (AMP) differed from LSD and DOM in that it enhanced the rate of acquisition to the light but not to the tone conditioned stimulus. There was no effect of d-2-bromol LSD on acquisition of conditioned responses to either conditioned stimulus. The order of potency for increasing the rate of conditioned response acquisition was: LSD > DOM > AMP for the light-conditioned stimulus and LSD > DOM for the tone-conditioned stimulus. Separate groups of rabbits received explicitly unpaired presentations of stimuli (tone alone, light alone and shock alone) to determe the nonassociative effects of these drugs on reponse production. LSD and AMP produced no increase in either base-line responding, responding to the tone and light stimuli or the amplitude of the unconditioned response to shock. The increased rate of acquisition of conditioned responses produced by LSD and AMP could apparently be attributed to an effect on associative factors. DOM had no effect on the amplitude of the of the unconditioned response to shock, but the highest dose used (3 .mu.mol/kd) did increase both base-line rate of responding and responding to tone and light stimuli. The increased rate of acquisition of conditioned responses produced by DOM was apparently due, at least at the highest dose, to some combination of effects on both associative and nonassociative factors. While LSD, DOM and AMP had the common effect of increasing the rate of acquisition of conditioned responses, AMP differed from LSD and DOM by having a selective effect on acquisition to the light conditioned stimulus. DOM differed from LSD and AMP by its effects on nonassociative contributors to conditioned response production.
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