Arterial pressure (AP) is lower in pre-menopausal women than in men of similar age. Pre-menopausal women exhibit a lower sympathetic outflow and a greater baroreceptor reflex, however molecular mechanisms for the gender differences of AP regulation are still not well understood. Since the hypothalmus is strongly functionnaly connected to the nucleus tractus solitarius (NTS), a pivotal region of the medulla oblongata for regulating the set-point of AP, we hypothesized that a different neuronal functions at the level of hypothalamus between men and women could contribute to the gender difference in cardiovascular homeostasis. Since females Spontaneous Hypertensive Rats (SHRs) clearly exhibit lower AP levels than their male counterparts at similar age, we investigated whether the hypothalamus of SHRs exhibit gender differences in gene expression by using microarray technique. Overall design: 2 groups of adult SHR rats (9 weeks old) were formed : males (n=5) and females(n=5). Hypothalamus was dissected from each rat and total RNAs were extracted. For each group, 100ng of total RNA from each rats were pooled together before being processed in the microarray experiment.