Renon S. Mical

Luteinizing hormone-releasing activity in hypophysial stalk blood and elevation by dopamine

Pituitary halves incubated in pituitary stalk plasma release more luteinizing hormone than their opposite halves incubated in plasma from peripheral blood. Glands incubated in stalk plasma from dopamine-treated rats release more luteinizing hormone than glands incubated in stalk plasma from untreated controls. Luteinizing hormone-releasing activity in stalk plasma may be due to the luteinizing hormone-releasing factor, and the secretion of luteinizing hormone-releasing factor may be controlled by a dopaminergic mechanism.

Neurovascular Regulation of the Anterior Hypophysis

Publisher Summary This chapter discusses neurovascular regulation of the anterior hypophysis. It explains some of the characteristics of the vascular link connecting the brain and the anterior pituitary to examine the role of the portal vessels as vehicles for the transference of hormones from the brain to the anterior pituitary and to evaluate the primary capillary plexus as a possible site of exchange of neurohormones. Moreover, there is very little data available concerning the flow of blood through the anterior pituitary of any species with the exception of the rat. The anterior pituitary of the rat receives blood through portal vessels only, and such a vascular arrangement appears to be typical of mammals. Two portal systems deliver blood to the anterior pituitary. One of these two systems consists of the primary capillaries in the median eminence of the hypothalamus and in the pituitary stalk plus the veins—the long portal vessels—which drain these capillary beds. The long portal vessels lie on the surface of the pituitary stalk. The other system consists of primary capillaries in the infundibular process of the posterior pituitary plus the veins—the short portal vessels—which drain these particular capillaries. The short portal vessels lie on the dorsal and anterior surfaces of the pituitary. The long portal vessels as well as the short portal vessels empty into the sinusoids of the anterior pituitary. These sinusoids constitute the secondary capillary plexus of the hypophysial portal vasculature. The chapter also discusses how the ventromedial region of the hypothalamus is a thin structure that forms the floor of the third ventricle.