[Hypothermia and paradoxical sleep. I. Pontile cats without hypothalamo-hypophysis]

Chronic pontile cats (without hypothalamo-hypophysis) were kept during 4 days at central T (TC) between 37.5 and 30.8 degrees C at stable ambiant T (TA) between 28.5 and 23 degrees C. The vasomotor index of the forepaw was chosen for studying change in vasomotricity. Small and slow variations of TA (+1.5 degrees C) around 27 degrees C were followed by thermoregulatory response since a progressive decrease of TA under 27 degrees C led to vasoconstriction and increase of TC while progressive increase of TA above 27 degrees C led to vasodilatation and decrease of TC. However rapid and large decrease of TA under 27 degrees C (24-23 degrees C) led to the expected hypothermia with decrease of TC but without vasoconstriction. Paradoxical sleep (PS) amounts were strongly correlated with TC. At TC above 35.5 degrees C PS was almost totally suppressed while it increased significantly under 35 degrees C (Q10 = 0.10). Under 35 degrees C at stable TC and TA, PS occurred with an endogenous circahoral rhythm which did not vary significantly between 35 and 32 degrees C. These results strongly suggest that in pontile cats, PS is both gated and regulated by TC, while TC is regulated by pontobulbar vasomotor systems in response to TA. The putative role of the ventro-lateral medulla, in controlling both vasomotricity, TC and the excitability of the locus coeruleus is discussed in relation with PS.