A SURVEY OF AMYGDALA CENTRALIS CARDIOVASCULAR RESPONSE TO ANGIOTENSIN I MICROINJECTION IN RENOVASCULAR HYPERTENSIVE RAT.

Previous studies have revealed that induction of two kidneys, one clip Goldblatt hypertension induction in rats eliminates hypertensive response after inactivating of the central nucleus of the amygdala. The present study investigated the possibility of alteration in local renin angiotensin system activity in central nucleus of the amygdala after hypertension induction and evaluation of cardiovascular response to angiotensin I microinjection into central nucleus of the amygdala in wistar rats.

Materials & Methods: 130 Wistar rats were studied in this investigation. Clamps were placed on the left renal arteries to induce two kidneys, one clip Goldblatt hypertension. A similar surgery procedure without clipping was done in sham group. The rats were studied eight weeks after surgery. The mean arterial blood pressure and heart rate were measured directly with indwelling arterial cannula under urethane anesthesia. Rats received bilateral cannulation of the central nucleus of the amygdala for angiotensin I microinjection. After bilateral microinjection of consecutive doses of angiotensin I (0.5µL- 10µM, 10�nM and 10�pM), saline and pretreatment of losartan (10 µ M), saralasin (1nM) or captopril (10 µ M) before Angiotensin I injection into central nucleus of the amygdala, mean arterial blood pressure and heart rate were measured and compared between groups.

Results: Bilateral microinjection of consecutive doses of angiotensin I into central nucleus of the amygdala significantly increased mean arterial blood pressure and heart rate in hypertensive group in comparison to normotensive one (P<0.001) . After pretreatment of saralasin and losartan the effects of 10nM angiotensin I microinjection into central nucleus of the amygdala of all groups were inhibited.

Captopril inhibits effects of angiotensin I in normotensive animals but does not in hypertensive ones.

Conclusion : These results are functionally demonstration of cardiovascular effects of angiotensin I microinjection into central nucleus of the amygdala and those effects have increased after 2K1C hypertension induction. This process may contribute in Goldblatt hypertension pathogenesis. Increased angiotensin II receptors or accelerated proteolytic process of angiotensin I to angiotensin II may alter angiotensin I microinjection into central nucleus of the amygdala outcome.