[7-D-ALA]-angiotensin-(1-7): selective antagonism of angiotensin-(1-7) in the rat paraventricular nucleus.

Microiontophoretic application of both, the octapeptide angiotensin II (Ang II) and its N-terminal heptapeptide angiotensin-(1-7), [Ang-(1-7)], has been shown to increase the firing rate of rat hypothalamic paraventricular neurones. In the present microiontophoretic study, the effect of the angiotensin analogue [7-D-Ala]-Ang-(1-7) on Ang II- and Ang-(1-7)-induced firing rate increase of paraventricular neurones has been tested. While the response to Ang II was unchanged, the response to Ang-(1-7) was effectively blocked by [7-D-Ala]-Ang-(1-7). The results indicate that the Ang-(1-7)-induced excitation of paraventricular neurones may be mediated by a distinct Ang-(1-7)-receptor and that [7-D-Ala]-Ang-(1-7) is a selective antagonist of this receptor.