Opposite actions of CCK-8 on amphetamine-induced hyperlocomotion and stereotypy following intracerebroventricular and intra-accumbens injections in rats.
Cholecystokinin-octapeptide (CCK-8) has recently been found to coexist with dopamine (DA) in a subpopulation of midbrain DA neurons. The present study investigated the functional nature of this coexistence by testing the effects of intracerebroventricular (ICV) and intra-nucleus accumbens (NAS) applications of CCK-8 in two behavioral assays of DA function (i.e., stimulant-induced hyperlocomotion and stereotypy). Rats were injected with 1 or 3 mg/kg of d-amphetamine sulfate (AMP) 15 minutes prior to ICV (2 micrograms) or intra-NAS (20 ng, 200 ng, or 2 micrograms) injections of CCK-8 or haloperidol (HAL; 5 micrograms). ICV administered CCK-8 was found to antagonize the locomotor stimulatory effects of the low AMP dose, while the same peptide treatment markedly potentiated the stereotypy produced by the high dose of AMP. Similar results were obtained when CCK-8 was microinjected directly into the NAS, with the strongest effects observed following the smallest (i.e., 20 micrograms) dose. These results suggest that both locomotor-antagonizing and stereotypy-potentiating effects of central CCK application depend on CCK-DA interactions in the nucleus accumbens.
Weiss
F
F
Department of Psychology, University of California, Santa Barbara 93106.
Tanzer
D J
DJ
Ettenberg
A
A
D000661:Amphetamine / Q000494:pharmacology*; D000818:Animals; D007267:Injections; D007276:Injections, Intraventricular; D008124:Locomotion / Q000187:drug effects*; D008297:Male; D009714:Nucleus Accumbens; D051381:Rats; D011919:Rats, Inbred Strains; D012844:Sincalide / Q000008:administration & dosage / Q000494:pharmacology*; D013239:Stereotyped Behavior / Q000187:drug effects*
D000661:Amphetamine; D012844:Sincalide