Concurrent Hyperglycemic and Pressor Effects of Median Forebrain Bundle Stimulation in Rats 1

Abstract

Plasma glucose and blood pressure were concurrently increased by electrical stimulation of the median forebrain bundle (MFB) at different points in urethane-anesthetized rats. Neither response was reduced after bilateral adrenalectomy. Interruption of sympathetic tone by blocking α-adrenergic receptors with phentolamine, or by cervical spinal section, prevented hyperglycemia and the initial phase of the biphasic pressor response. In contrast, the secondary pressor phase was unaffected by these procedures but was abolished following hypophysectomy. Our results indicate that while hyperglycemia and the initial pressor phase were caused by sympathetic hyperactivity, the secondary pressor phase could be due to release of hormones like vasopressin from the neurohypophysis. Because hyperglycemic and pressor effects were elicited simultaneously from the MFB which interconnects various hypothalamic nuclei, it was considered possible that hypothalamic dysfunction could be a common denominator in elevating plasma glucose and blood pressure whenever diabetes and hypertension coexist.