Increases in cytosolic Ca²⁺ in rat area postrema/mNTS neurons produced by angiotensin II and arginine-vasopressin

It is well established that neurons in the dorsal medulla, including the area postrema and the medial nucleus tractus solitarius (mNTS), are involved in the central actions of circulating peptides such as angiotensin II (ANG II) and arginine vasopressin (AVP). This report describes a reparation that permits the identification and maintenance of area postrema/mNTS neurons in culture in which the cellular and potentially subcellular responses to neurotransmitters and neuropeptides on area postrema/mNTS cells can be investigated. Following 15-21 days in culture, the effects of ANG II and AVP on changes in intracellular Ca²⁺ concentration ([Ca²⁺]_i) were examined. Both ANG II and AVP resulted in a rapid and transient increase in [Ca²⁺]_i reaching maximum in 15 s and returning towards baseline values within 180 s. The ANG II-mediated increase in [Ca²⁺]_i was almost completely abolished by the selective angiotensin AT₁ receptor subtype antagonist, losartan (DuP 753). These results suggest that ANG II and AVP modulate area postrema/mNTS neuronal activity by increasing intracellular Ca²⁺.