Inhibition of pyrogen Escherichia coli fever with intracerebral administration of prazosin, dihydrobenzperidol and nifedipin in the rabbits.

1. The thermoregulatory, effector processes were investigated after treatment with prazosin (PRA), dihydrobenzperidol (DHBP) and nifedipin (ADA) applied to the thermosensitive zone of the anterior hypothalamus (PO/AH) on normothermic and feverish rabbits (LPS, lipopolysaccharide E. coli; 1 meg/kg, i.v.). 2. The alpha 1-noradrenergic receptor antagonists, PRA and DHBP, applied to the PO/AH produced an abolishment of fever elicited by pyrogen i.v. injection mainly because of vasodilation of ear skin vessels and attenuation of metabolic rate. 3. Calcium channel blocker, ADA, also induced a decline in the rabbit's core temperature in the same manner. 4. All these drugs given to the PO/AH did not change the body temperature in normothermic rabbits. 5. These results, therefore, strongly suggest that alpha 1-noradrenergic receptors subserve the coordinated thermoregulatory mechanisms in PO/AH which are required for antipyresis. The inhibition of Ca2+ turnover is discussed as a possible mechanism of antipyretic action of these drugs given to the PO/AH.