The effects of stimulation of the hypothalamic paraventricular nucleus (PVN) by l-glutamate on blood pressure and ongoing activities of adrenal and renal sympathetic nerves were examined in anesthetized rats. Microinjection of excitatory amino acid, l-glutamate (100 nmol in 200 nl saline), into the unilateral PVN resulted in an increase in the ipsilateral adrenal nerve activity, while it resulted in decreases in renal nerve activity and arterial blood pressure. After severance of bilateral carotid sinus and vagal nerves, the decreased response of blood pressure to the same stimulus did not change, while the decreased response of renal nerve activity was almost abolished, and the increased response of adrenal nerve activity still remained, though it slightly attenuated. The involvements of baroreceptor afferents and vagal afferents in these responses were discussed.
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