Drugs that selectively block D(2) receptors are known to provoke a rapid cell firing increase followed by A9 and A10 dopaminergic (DA) neuron inactivation (depolarization block). In this study, possible relationships between cell firing rapid increase and specific behavioral effects, linked to sensorimotor integration, were investigated in the rat. To this purpose, with the aid of a video camera apparatus and a frame-by-frame analysis, effects of sulpiride-induced blockade of DA D(2) receptors were analyzed on the orienting movement of the head induced by acoustic stimulation. In a control group of rats, during trials lasting 20 min, latency and duration of head turning (HT) were 186.15 +/- 51.66 ms and 266.87 +/- 47.49 ms, respectively. Sulpiride injection (20,40,100 mg/kg IP) provoked a dose-dependent increase of HT latency and duration; however, only latencies showed statistically significant variations. It is suggested that cell firing rapid increase, observed on A9 and A10 DA neurons, following sulpiride administration, may be correlated to rapid modifications of specific HT parameters linked to sensorimotor integration.