EFFECT OF ANGIOTENSIN Ⅱ RECEPTOR SUBTYPE Ⅰ ON THE FIRING RATE IN CATECHOLAMINERGIC TUMOR CELLS

Objective To study the action of brain angiotensin Ⅱ (Ang Ⅱ) receptors and underlying intracellular mechanism in the catecholaminergic system(CATH) Methods Action potentials (APs) of the primary cocultured catecholaminergic tumor (CATH. a) cells were recorded with the whole-cell patch clamp configuration in current clamp mode. Expression of Ang Ⅱ receptors subtypes (AT1 and AT2 ) was detected by RT-PCR technique. Results The differentiated CATH. a cells represented a neuron-like characterization. All CATH. a cells expressed mRNA encoding both Ang Ⅱ AT1 and AT2receptor subtypes. Ang Ⅱ increased the firing rate in the CATH. a cells, which was inhibited completely by addition administration of the AT1 but not AT2 receptor antagonist, and partially by using the inhibitors of signal molecules, U73122 (10μmol·L^-1 ), or KN-93(10μmol·L^-1 ), or calphostin C (10μmol·L^-1).Conclusion Ang Ⅱ increases firing rate in CATH. a cells via AT2 receptor. The CATH. a cells expressing functional AT1 and AT2 rfceptor subtypes may be of general utility for the study of the Ang Ⅱ receptor-induced modulation of brain catecholaminergic system.

完成机构：[1]DepartmentofPhysiology,MedicalSchoolofXi'anJiaotongUniversity,Xi'an710061,China. [2]DepartmentofPhysiology,CollegeofMedicine,UniversityofFlorida,U.S.At