Hypothalamic temperature during desynchronized sleep.

The influence of changes in heat loss at specific heat exchangers, appraised by recording ear skin temperature (Ts), on the hypothalamic temperature (Thy) rise during desynchronized sleep (DS) was studied in unrestrained cats at different ambient temperatures (Ta). The correlations of initial and final Thy changes (delta iThy and delta fThy) with initial and final Ts changes (delta iTs and delta fTs), respectively, are statistically not significant. However, a significant negative correlation was found between delta fiThy, i.e. delta fThy-delta iThy, and delta fiTs, i.e. delta fTs-delta iTs. The latter result shows that only after its initial rise is Thy affected by changes in heat loss at specific heat exchangers during DS. Accordingly, delta fThy and delta fiThy are positively correlated with Ta. However, also delta iThy, although not affected by heat loss changes at specific heat exchangers, shows a positive correlation with Ta. On the basis of these results and of the data in the literature, it is concluded that three independent factors underlie Thy changes during DS, namely heat loss at specific heat exchangers, hypothalamic blood flow and thermogenesis.