The GABA(a) agonist muscimol enhances locomotor activity, but does not alter the behavioural effects of CRH in juvenile spring chinook salmon (Oncorhynchus tshawytscha)

The present study investigated the effects of manipulating the GABAergic sy stem on locomotor activity in juvenile spring chinook salmon, Oncorhynchus tshawytscha. In addition, we evaluated whether the GABAergic system is impo rtant for mediating the behavioural effects of corticotropin-releasing horm one (CRH). An intracerebroventricular (ICV) injection of the GABA(a) agonis t muscimol caused an acute and dose dependent increase in locomotor activit y in juvenile spring chinook salmon. ICV injections of the GABA(a) antagoni st bicuculline prevented the increase in activity when administered concurr ently with muscimol. The GABA(b) agonist baclofen had no effect on locomoto r activity in this study. Furthermore, we found no evidence that the locomo tor response to exogenous CRH was altered by the concurrent administration of muscimol or bicuculline. These results provide evidence to support the h ypothesis that endogenous GABA within the central nervous system is involve d in the control of locomotor activity in fish. The data also suggest that there is no interaction between the GABAergic system and CRH with regards t o the control of locomotor activity in this species.