Temperature dependence of agonist binding to muscarinic receptors in rat hypothalamic regions

The temperature dependence of the muscarinic binding characteristics in various brain regions was investigated at 25° and 37°. An unusual degree of temperature dependence was observed for agonist binding parameters in the hypothalamus, especially in the preoptic area. We therefore chose this region for a more detailed study over a temperature range of 25°-42°. Changes due to temperature alterations in the proportion of high-affinity sites, as well as in the high-affinity state constant, were found in male rats, while in females at the proestrous stage only the high-affinity constant was affected. The possible involvement of the muscarinic system is discussed in light of the well known role of the hypothalamus in body thermoregulation.