mr-1452 and bremazocine

The effects of bremazocine on memory processes were studied in DBA/2 mice tested in a passive avoidance apparatus. In a first set of experiments, memory impairments following immediately posttraining bremazocine administration (0.025 and 0.05 but not 0.01 mg/kg), and memory improvements following immediately posttraining administration of the kappa-opioid-receptor antagonist MR-1452 (1.0 and 2.0 but not 0.5 mg/kg), were observed. No effect was evident when the drugs were injected starting 120 min after training. In a second set of experiments, the effects of bremazocine (0.05 mg/kg) were antagonized by a per se ineffective dose of MR-1452 (0.5 mg/kg), suggesting involvement of kappa-opioid-receptors. In a third set of experiments, the effects of bremazocine were enhanced by a per se ineffective (15 min) immobilization stress, and were decreased by familiarization with the passive avoidance apparatus. The results are discussed in terms of attenuation of emotionality following bremazocine administration.

Topics: Analgesics; Animals; Avoidance Learning; Benzomorphans; Male; Mice; Mice, Inbred DBA; Morphinans; Narcotic Antagonists; Restraint, Physical; Stress, Psychological

The effects of the benzomorphan analogue bremazocine on locomotor activity were studied in DBA/2 (DBA) and C57BL/6 (C57) mice. Three sets of experiments were carried out. In a first set, bremazocine depressed activity in both strains, but DBA mice were more sensitive to the effects of the drug. In a second set of experiments the effects of bremazocine were antagonized by a per se ineffective dose (0.5 mg/kg) of the selective kappa-opioid receptor antagonist MR 1452, showing that they were mediated through an interaction with this sub-population of opioid receptors. In a third set of experiments the effects of bremazocine were enhanced by the administration of a per se ineffective dose (0.025 mg/kg) of haloperidol, showing the involvement of dopaminergic mechanisms.

Topics: Analgesics; Animals; Benzomorphans; Haloperidol; Male; Mice; Mice, Inbred C57BL; Mice, Inbred DBA; Morphinans; Motor Activity; Narcotic Antagonists; Receptors, Dopamine; Species Specificity