EFFECTS OF NIMODIPINE AND NIFEDIPINE UPON BEHAVIOR AND REGIONAL BRAINMONOAMINES IN THE RAT

The effects of single and repeated (9 times) administration of two dih ydropyridines (DHPs), nimodipine (NIM) and nifedipine (NIF) (5 mg/kg p er 12 h and 2.5 mg/kg per 12 h, IP), on the behavior of male adult rat s in the holeboard and in the plus-maze, were investigated. Besides, t he effects of repeated administration of the drugs on the levels of do pamine (DA), serotonin (5-HT), and their respective major metabolites in several regions of the central nervous system (CNS) were also asses sed. The effects of single and repeated administration of the drugs we re similar. Both DHPs caused a significant decrease in general motor a ctivity which was evident in both tests and more marked with the highe r doses. The two exploratory parameters measured in the holeboard, i.e . head-dipping frequency and duration, were dissociated under pharmaco logical treatment. The drug-treated animals did not show an increased emotionality in the holeboard. However, in the plus-maze, NIF (5 mg/kg ) and to a lesser extent NIM, appeared to induce some anxiety-related responses which may be secondary, at least in part, to the depressing effect on activity and exploration. Repeated administration of NIM and NIF caused an increase in striatal DA and DOPAC levels, whilst no eff ects were found on serotonergic system in any of the regions of the CN S analyzed.