A pontine-hypothalamic temperature difference correlated with cutaneous and respiratory heat loss

The role of cutaneous and respiratory heat loss for selective brain cooling in different species is discussed and new experimental results from a comp arative study are summarized. In three species (cat, rabbit and rat) the di fference between pontine and hypothalamic temperatures was studied as a fun ction of head heat exchanger vasomotion appraised by the difference between hypothalamic and ear pinna (cats and rabbits) or nasal mucosa (rats) tempe ratures during the behavioral states of wakefulness and slow wave sleep at an ambient temperature of 24 +/- 1 degrees C. The results show that: (i) th e pontine-hypothalamic temperature difference is an useful indicator of sel ective brain cooling since it is positive and inversely correlated with the hypothalamic-ear pinna temperature difference in cats and rabbits and with the hypothalamic-nasal mucosa temperature difference in rats; (ii) respira tory heat loss prevails quantitatively over cutaneous heat loss in maintain ing this difference. (C) 1998 Elsevier Science B.V. All rights reserved.