Interaction between "mental stress" and baroreceptor reflexes concerning effects on heart rate, mean arterial pressure and renal sympathetic activity in conscious spontaneously hypertensive rats.

Spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY) were compared concerning the interactions between cortico-hypothalamic alerting responses and baroreflex influences on neurogenic cardiovascular control. For this purpose mean arterial pressure (MAP), heart rate (HR) and renal sympathetic nerve activity (RSNA) were continuously recorded during night time in conscious, otherwise undisturbed rats. Baroreceptor sensitivity was assessed as percentage HR and RSNA reductions per mmHg MAP elevation when a standardized phenylephrine infusion was performed. A state of acute "mental stress" could be induced by a likewise standardized sudden blowing of air. These two opposing influences on neurogenic cardiovascular control were also experimentally superimposed in various ways and the effects on MAP, HR and RSNA followed. During "rest" RSNA was higher in SHR than in WKY and it also increased more during "mental stress". The baroreflex sensitivity was clearly reduced in SHR and WKY concerning HR reduction (0.44 +/- 0.06 vs. 0.78 +/- 0.08%/mmHg; p less than 0.01) but not so concerning RSNA, which was similar in SHR and WKY (2.6 +/- 0.2 vs. 2.9 +/- 0.4%/mmHg). If expressed (HR + 1 +/- 3%; p less than 0.025 vs. SHR and RSNA + 11% +/- 10, p less than 0.01 vs. SHR). These results) (0.10 +/- 0.02 vs. 0.06 +/- 0.01 microV/mmHg; p less than 0.12). Also single fibre recordings in anaesthetized rats showed the same principle difference between SHR and WKY.(ABSTRACT TRUNCATED AT 250 WORDS)