Effects of selective cutaneous denervation on hypothalamic thermosensitivity in rats

The effect of altering input from cutaneous thermoreceptors of the face and trunk on the relationship between hypothalamic temperature (T _hy) and heat production (HP) was studied in three rats. The signal from cutaneous receptors was altered in two ways: by altering skin temperature (T _sk) and by sectioning nerves supplying cutaneous receptors. It was found that whenT _sk was lowered in normal ratsT _hy threshold for thermoregulatory HP was elevated, but the slope of the relationship betweenT _hy and HP was not significantly altered. After the spinal nerves serving the trunk skin were sectioned, the slope was reduced and the threshold was elevated markedly at both test ambient temperatures (T _a), butT _a had essentially the same effect on theT _hy vs. HP relationship after cutaneous denervation as before. Clearly, eliminating input from trunk cutaneous thermoreceptors has a different effect than does lowering or raisingT _sk, but thermoregulation is being achieved by the same basic mechanism before and after cutaneous denervation. After the cranial nerves supplying the skin of the face were also sectioned, there was a further elevation in theT _hy threshold for HP atT _a=25° C but no change atT _a=15°C. It is concluded that cutaneous denervation does not substantially interfere with the rat's ability to regulate its body temperature, and that the reduced Thy sensitivity and increased Thy threshold exhibited after cutaneous denervation is the result of input from intact warm- and cold-thermoreceptors located in the core and in tissues intermediate to core and skin.