Renal and cutaneous vasomotor and respiratory rate adjustments to peripheral cold and warm stimuli and to bacterial endotoxin in conscious rabbits.

In conscious rabbits peripheral cold stimuli decreased respiratory rate and increased cutaneous vasomotor tone while simultaneously renal sympathetic nervous discharge decreased. Peripheral warm stimuli produced the reverse pattern of autonomic effector activity. Injection of a bacterial endotoxin at warm ambient temperature elicited a biphasic fever response. Within the first 60 min cutaneous vasomotor tone increased, simultaneously renal sympathetic activity decreased. Therefore, ear skin vessels dilated and renal sympathetic activity increased by about 100%. Respiratory rate remained depressed during both fever phases. Renal blood flow was investigated in a second series of experiments and showed a negative stimulation but only in the first phase of fever. The results show that renal innervation is involved in the typical thermoregulatory autonomic activity pattern by which temperature homeostasis is preserved. The vasomotor patterns of cold and heat stress developing during fever are compatible with the concept of a changed set-point of the body thermostat. The depressed respiratory rate and the lack of the renal vascular response to the increased nervous activity during the second fever phase and their reversal to normal after acetylsalicylate (ASA) indicate the participation of prostaglandins modifying peripheral and central neurotransmitter mechanisms.