Perfusion of the preoptic area with muscimol or prostaglandin E2 stimulates cardiovascular function in anesthetized rats.

The effect of unilateral perfusion of the preoptic area (POA) utilizing in vivo microdialysis with the GABAergic agonist, muscimol, or prostaglandin E2 (PGE2) on cardiovascular function (heart rate, blood pressure and cutaneous blood flow) was determined in halothane-anesthetized rats. Perfusion of muscimol or PGE2 increased the heart rate, 55 +/- 6 beats/min and 69 +/- 12 betas/min, respectively (P < 0.01). Cutaneous paw blood flow tended to decrease. Blood pressure did not change in response to the perfusion of muscimol, but increased 9 mmHg in response to the perfusion of PGE2 (P < 0.01). The increases in heart rate and blood pressure were blocked by systemic administration of propranolol or adrenalectomy (P < 0.01), suggesting that these effects were due to the activation of the sympathetic innervation of the heart or adrenal gland. It is proposed that the POA provides a tonic inhibitory afferent to posterior hypothalamus neurons which regulate cardiovascular function.