The effects of concurrent D-1 and D-2 dopamine receptor blockade with sch 23390 and eticlopride, on bombesin-induced behaviours

Hugh Piggins and Zulfiquar Merali. The effects of concurrent D-1 and D-2 dopamine receptor blockade with SCH 23390 and eticlopride, on bombesin-induced behaviours. Prog. Neuro-Psychopharmacol. & Biol. Psychiat. 1989, 13: 583-594. 1. The objective of the current study was to assess the effect of concurrent D-1 and D-2 receptor blockade on bombesin (BN)-induced grooming and locomotion on the premise that dopamine could be mediating the behavioural effects of BN. 2. Rats implanted with ventricular cannulae were pretretreated systemically with SCH 23390 and/or eticlopride (ETIC) followed by BN (0.5 ug/3 ul; i.c.v.). Grooming and locomotory activity were assessed for 60 min. 3. Individually, SCH 23390 (0.033 mg/kg) and ETIC (0.05 mg/kg) significantly inhibited BN-elicited grooming but not locomotion. Combining ETIC (0.05-0.1 mg/kg) with the fixed dose of SCH 23390 (0.033 mg/kg) significantly inhibited both behaviours in a dose dependent manner with a greater effect on locomotion. Adding SCH 23390 (0.033-0.075 mg/kg) to ETIC (0.05 mg/kg) inhibited both behaviours in a dose dependent manner with a more pronounced effect on grooming. At the combination dosages utilized, SCH 23390 and/or ETIC failed to significantly alter baseline behaviours in control conditions. It is thus concluded that both dopamine receptor subtypes are involved in the expression of BN-induced behaviours with D-1 appearing to have a greater involvement with grooming and D-2 locomotion.