The hypothalamo-hypophyseal neurosecretory system of the ring-necked snake, Diadophis punctatus

Abstract

The hypothalamo-hypophyseal neurosecretory system was studied in the ring-necked snake Diadophis punetatus. The appearance of neurosecretory material in the hypothalamus, median eminence and pars nervosa is described on the basis of sections stained with Gomori's aldehyde fuchsin. Intraperitoneal injections of sodium chloride caused marked depletion of neurosecretory material in the nucleus paraventricularis, hypothalamo-hypophyseal tract, and pars nervosa. No corresponding change was observed in the nucleus supraopticus. Snakes dehydrated by withholding water and subjected to forced air for several days showed a distinct decrease in neurosecretory material. In animals injected with vasopressin and oxytocin, increases in stainable material were seen in all parts of the system. There was also an increase in the number of cells containing secretory material in the paraventricular nuclei, with groups of cells becoming especially evident in the peripheral areas of the nuclei. These results suggest that the hypothalamic centers, in particular, the paraventricular nuclei, function in salt and water metabolism in Diadophis punctatus.