Feeding and temperature changes in sheep following injections of barbiturates, Ca-++, or Mg-++ into the lateral, third, or fourth ventricle or cerebral aqueduct.

Eleven sheep were prepared with cannula guides directed toward four areas within the ventricular system to determine effective sites of action of chemicals which when injected into the cerebrospinal fluid produce changes in feeding behavior and temperature regulation. Pentobarbital, barbital, calcium chloride, and magnesium chloride elicited feeding in sheep when injected into the third ventricle or into the cerebral aqueduct; however, feeding response was less after injections into the latter. Pentobarbital and magnesium chloride elicited an increase in body temperature when injected into the third ventricle but not when injected into the cerebral aqueduct. Perfusions (push-pull) of the lateral and third ventricles with calcium chloride and magnesium chloride solutions (50 mM) resulted in feeding while similar perfusions of the fourth ventricle resulted in no response. Responses to lateral and third ventricular injections presumably involved effects on both anterior and posterior hypothalamic areas while injections into the cerebral aqueduct, due to the caudal flux of the cerebrospinal fluid, may have affected primarily only the posterior hypothalamus and more caudal structures. The feeding response probably resulted from depression of neural fibers which inhibit feeding.