Maternal influences on sympathetic-adrenal medullary system in spontaneously hypertensive rats

The technique of reciprocal cross fostering was used to assess the influence of the maternal environment on the functioning of the sympathetic-adrenal medullary system in the spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) normotensive rats. Control, in-fostered, and cross-fostered rats were tested in adulthood to assess 1) the neural contribution to resting mean arterial blood pressure (MAP) and 2) sympathetic-adrenal medullary responses to acute footshock stress. Adult resting MAP was significantly lower in cross-fostered SHRs (139.6 mmHg) compared with control or in-fostered SHRs (162.1 and 159.3 mmHg). In addition, the decrease in MAP after sympathetic blockade (40.6 mmHg) was significantly less in cross-fostered SHRs compared with controls (50.1 mmHg). Sympathetic-adrenal medullary responses to foot-shock were greater in SHR than WKY rats; however, cross-fostered SHRs showed exaggerated responses compared with control and in-fostered SHRs. Altering the maternal environment did not produce any measurable effects on the neural contribution to resting MAP or sympathetic-adrenal medullary responsivity to acute stress in the WKY strain. These results indicate that the blood pressure-lowering effect of cross fostering in the SHR strain is caused in part by a dampening of the neural contribution to resting MAP; however, these animals retain their strain's characteristic adrenergic hyperreactivity to stressful stimulation.