Adenosine acts at many sites to modulate neuronal activity. The nucleus tractus solitarii (NTS) is a major brain site in cardiovascular control. The present study was undertaken for a detailed analysis of the distribution of A(1) adenosine receptor (A(1)R) in the NTS of spontaneously hypertensive rats (SHR) and Wistar Kyoto (WKY), using in vitro autoradiography with [(3)H]DPCPX. The density of [(3)H]DPCPX in the whole NTS decreased according to the rostral-caudal levels. This high level of [(3)H]DPCPX binding at rostral sites is due to an specific label of the dorsomedial/dorsolateral subnuclei. On the other hand, analysis of subpostremal subnucleus, showed opposite results. The density of [(3)H]DPCPX binding in the subpostremal NTS increased according to the rostral-caudal levels. Furthermore, it was observed an increased [(3)H]DPCPX binding in the SHR compared with WKY. The results show a complex pattern of A(1)R distribution in the NTS, which highlight the powerful modulatory actions mediated by adenosine in the NTS barosensitive neurons.