CROSS-SENSITIZATION BETWEEN PHENCYCLIDINE AND (-)PENTAZOCINE BUT NOT (+)PENTAZOCINE

Repeated administration of psychomotor stimulants such as amphetamine and cocaine, and psychotomimetics such as phencyclidine, produce progr essively enhanced behavioral effects, a phenomenon known as behavioral sensitization. Little is known about the effects of repeated treatmen t with sigma ligands on locomotor activity. The present research deter mined the psychomotor stimulant effects of the sigma ligand (+)pentazo cine and its enantiomer; and investigated whether reciprocal cross-sen sitization occurs between them and PCP-induced locomotor activity and ambulation. Adult female Sprague-Dawley rats were used. Total locomoto r activity and ambulation were assessed with an automated photoelectri c system. Acute (+) or (-)pentazocine given IP produced slight but ins ignificant locomotor stimulant effects. Repeated administration of (+) pentazocine failed to produce behavioral sensitization. However, four repeated injections of (-)pentazocine or PCP produced behavioral sensi tization. (-)Pentazocine sensitized rats showed cross-sensitization to PCP-induced locomotion and ambulation. Furthermore, PCP sensitized ra ts showed cross-sensitization to (-)pentazocine-induced locomotion and ambulation. These findings suggest that (+) and (-)pentazocine act at different receptor sites. (-)Pentazocine is more similar to PCP in pr oducing locomotor stimulant effects. Copyright (C) 1997 Elsevier Scien ce Inc.