Calcium ions are widely accepted as critically important in responses of neurons 
to a stimulus. We have show previously the central involvement of angiotensin II 
(ANGII) in water intake. This study determined whether voltage-dependent calcium 
channels are involved in ANGII-induced behavioral drinking implicating nitrergic 
mechanism. The antidipsogenic actions of L-type calcium channel antagonists 
nifedipine, on ANGII-induced drinking behavior were studied when it is injected 
into the median preoptic nucleus (MnPO). The influence of nitric oxide (NO) on 
nifedipine antidipsogenic action was also studied by utilizing the 
N(W)-nitro-L-arginine methyl ester (L-NAME) a constitutive nitric oxide synthase 
inhibitor constitutive (cNOSI) and 7-nitroindazol (7-NIT) a specific neuronal 
nitric oxide synthase inhibitor (nNOSI) and L-arginine a NO donor. Rats 200-250 
g, with cannulae implanted into MnPO, pre-treated into MnPO with either 
nifedipine, followed by ANGII, drank significantly less water than controls 
during the first 15 min after injection. However, L-NAME potentiated the 
dipsogenic effect of ANGII that is blocked by prior injection of nifedipine and 
L-arginine. 7-NIT injected prior to ANGII into MnPO also potentiated the 
dipsogenic effect of ANGII but with a less intensity than L-NAME that it is also 
blocked by prior injection of nifedipine. The results described in this paper 
provide evidence that calcium channels play important roles in the ANGII-induced 
behavioral water intake. The structures containing NO in the brain such as MnPO 
include both endothelial cells and neurons might be responsible for the 
influence of nifedipine on dipsogenic effect of ANGII. These data shows the 
correlation between L-type calcium channel and a free radical gas NO produced 
endogenously from amino acids L-arginine by endothelial and neuronal NO synthase 
in the control of ANGII-dipsogenic effect. This suggests that an L-type calcium 
channel participates in both short- and longer-term neuronal actions of ANGII by 
nitrergic way.