ROLE OF PREOPTIC-NEUROHYPOPHYSIAL SYSTEM IN WATER ECONOMY OF TOAD BUFO BUFO L

The effect of neurohypophysectomy or of lesions in the preoptic region of the hypothalamus on water balance was studied in the toad Bufo bufo. In the majority of the lesion-bearing toads, few or no surviving cells were found in the preoptic nuclei, and the neurosecretory material in the pars nervosa was significantly reduced to completely absent. The operations had little effect on the antidiuretic response to moderate dehydration or on the increased cutaneous water permeability caused by severe dehydration. There was no correlation between the response to dehydration and the completeness of elimination of the preoptic-neurohypophysial system. An attempt has been made to delineate the role played by the preoptic-neurohypophysial system in the water economy of the toad. It seems that the antidiuretic response to an osmotic load and an increased permeability of the urinary bladder to water may largely depend upon a functioning preoptic-neurohypophysial system. In the absence of the neurohypophysis the system appears unable to exert its functions in the water economy of the toad. © 1969.