Effect of nimodipine on drinking behavior measured in the runway: comparison and interaction with (+/-)-amphetamine

The aim of the present study was to evaluate the ability of the calcium channel blocker (CCE), nimodipine (NIM), to interact with (+/-)-amphetamine (AMPH) in modifying ingestive behavior. Rats performed in a water-reinforced runway paradigm with multiple trials. Water was available in sufficient quantity to produce satiety under control conditions as measured by a decline in response rate over the session. NIM and AMPH, given alone, did not produce significant effects on performance but produced behavioral changes when administered in combination. In particular, the combination of the highest doses (13 mg/kg i.p. NIM plus 0.56 mg/kg i.p. AMPH) initially depressed both running and drinking, whereas in later trials it increased running rate, without producing a parallel increase in water intake. These results suggest that NIM enhances AMPH-produced inhibition of drinking, whereas it first depresses and then enhances the AMPH-mediated runway performance, suggesting the rate dependency of this latter effect.