title: Behavioral sensitization: characterization of enduring changes in rotational behavior produced by intermittent injections of amphetamine in male and female rats.
abstract: Factors influencing the behavioral sensitization ("reverse tolerance") produced by intermittent amphetamine (AMPH) injections were studied by quantifying rotational behavior in rats that had a unilateral 6-hydroxy-dopamine lesion of the substantia nigra. The results indicate that: a single injection of a low dose of AMPH enhances rotational behavior induced by a second injection of AMPH for up to 12 weeks; multiple, weekly injections of AMPH produce a progressive enhancement in rotational behavior, over-and-above that produced by a single injection; female rats show more robust sensitization than males following single or multiple injections of AMPH; this sex difference may be due to the suppression of sensitization by an androgen, because removal of testicular hormones potentiates sensitization; the long-lasting sensitization of rotational behavior produced by infrequent injections of AMPH is not due to drug-environment conditioning effects, but perhaps to a persistent AMPH-induced change(s) in brain catecholamine systems; and a simple change in DA receptors is probably not involved, because the sensitization produced by infrequent injections of AMPH does not influence the rotation produced by a subsequent injection of apomorphine. The results illustrate an intriguing example of neuroplasticity that may have clinical relevance.
mesh_terms: D000661:Amphetamine / Q000494:pharmacology*; D000818:Animals; D001058:Apomorphine / Q000494:pharmacology; D001923:Brain Chemistry / Q000187:drug effects; D002369:Castration; D003216:Conditioning, Operant / Q000187:drug effects; D004361:Drug Tolerance; D005260:Female; D012739:Gonadal Steroid Hormones / Q000494:pharmacology; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D012737:Sex Factors; D013239:Stereotyped Behavior / Q000187:drug effects; D013997:Time Factors
chemical_list: D012739:Gonadal Steroid Hormones; D000661:Amphetamine; D001058:Apomorphine