Calcium Suppresses Central Angiotensin II Pressor Response Less in Shr

Hiroshi Itoh Second Department of Medicine, Kyoto Prefectural University of Medicine, Kawaramachi Hirokoji, Kamikyo-ku, Kyoto, 602, Japan

Kazuo Takeda Second Department of Medicine, Kyoto Prefectural University of Medicine, Kawaramachi Hirokoji, Kamikyo-ku, Kyoto, 602, Japan

Motoo Tanaka Second Department of Medicine, Kyoto Prefectural University of Medicine, Kawaramachi Hirokoji, Kamikyo-ku, Kyoto, 602, Japan

Masahiro Hirata Second Department of Medicine, Kyoto Prefectural University of Medicine, Kawaramachi Hirokoji, Kamikyo-ku, Kyoto, 602, Japan

Shingo Kawasaki Second Department of Medicine, Kyoto Prefectural University of Medicine, Kawaramachi Hirokoji, Kamikyo-ku, Kyoto, 602, Japan

Junko Hayashi Second Department of Medicine, Kyoto Prefectural University of Medicine, Kawaramachi Hirokoji, Kamikyo-ku, Kyoto, 602, Japan

Minako Oguro Second Department of Medicine, Kyoto Prefectural University of Medicine, Kawaramachi Hirokoji, Kamikyo-ku, Kyoto, 602, Japan

Susumu Sasaki Second Department of Medicine, Kyoto Prefectural University of Medicine, Kawaramachi Hirokoji, Kamikyo-ku, Kyoto, 602, Japan

Masao Nakagawa Second Department of Medicine, Kyoto Prefectural University of Medicine, Kawaramachi Hirokoji, Kamikyo-ku, Kyoto, 602, Japan

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Abstract

To determine whether calcium alters central cardiovascular regulation, cardiovascular responses to intracerebroventricular (ICV) injection of calcium were recorded in conscious Wistar rats. Calcium injection consistently produced dose-dependent decreases in mean parterial pressure and heart rate. Pretreatment with a calcium channel blocker, diltiazem, attenuated cardiovascular responses to calcium. Decreases in plasma norepinephrine indicated the contribution of sympatho-inhibition to vasodepression by calcium. Preceding calcium injection reduced pressor responses to ICV-injected angiotensin II. These findings suggest that there is a pharmacological interaction between calcium and angiotensin II in the central nervous system.

In spontaneously hypertensive rats (SHR), cardiovascular responses to calcium was larger than Wistar Kyoto rats (WKY). By contrast, calcium reduced pressor responses to angiotensin II only in WKY but not in SHR. Because the central interaction between calcium and angiotensin II has been different in SHR, our results imply that this difference may be related to the maintenance of high blood pressure in SHR.

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Calcium Suppresses Central Angiotensin II Pressor Response Less in Shr

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Calcium Suppresses Central Angiotensin II Pressor Response Less in Shr

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