Locomotor-activating effects of the D2 agonist bromocriptine show environment-specific sensitization following repeated injections.
Biphasic effects of bromocriptine (2.0, 5.0, 10.0, and 20.0 mg/kg IP) on locomotion were quantified in photocell activity boxes in rats. Following early suppression of activity, bromocriptine produced a clear, dose-dependent increase in locomotion that lasted several hours. When a low dose of bromocriptine (5.0 mg/kg) was administered daily over a 3-week period, the locomotor-activating effects of the drug showed progressive enhancement over days. The sensitization was environment specific; rats administered bromocriptine six times in the home cage showed no sign of a sensitized response to bromocriptine when subsequently tested in the activity box. Thus, selective stimulation of D2 receptors stimulates locomotion and sensitizes animals to subsequent injections, just as do the indirect-acting dopamine agonists cocaine and amphetamine.
Hoffman
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Department of Psychology, Concordia University, Montreal, Canada.
Wise
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RA
D000818:Animals; D001971:Bromocriptine / Q000008:administration & dosage / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004777:Environment; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D051381:Rats; D011954:Receptors, Dopamine / Q000187:drug effects*; D017448:Receptors, Dopamine D2
D011954:Receptors, Dopamine; D017448:Receptors, Dopamine D2; D001971:Bromocriptine