POSSIBLE THERMOREGULATORY ROLE OF UROCORTIN 1 NEURONS IN THE CENTRALLY PROJECTING EDINGER-WESTPHAL NUCLEUS IN RATS
The involvement of Urocortin 1 (Ucn1) expressing neurons in the centrally projecting Edinger-Westphal nucleus (cpEW) has already been confirmed in stress adaptation response and in the regulation of the energy balance. Morphological and functional experiments showed the presence of orexigenic and anorexigenic peptides and their receptors (MCR) in the cpEW. The role of the hypothalamic melanocortin system in the control of energy homeostasis is also well known, however its interaction with cpEW-Ucn1 has not yet been fully elucidated.We hypothesized first that Ucn1 neurons besides MC4R also carry MC3R. We supposed also that different environmental temperatures may influence MC3R and Ucn1 expression in cpEW. In the third step we applied a targeted neurotoxin ablation tool to reduce the number of MC3R-MC4R-Ucn1 neurons. Here we put forward that the absence of MC3R-MC4R-Ucn1 cells will result in inefficient accommodation to the change of the environmental temperature. Our results showed, MC4R expressing Ucn1 neurons also carry MC3R. We detected increased MC3R mRNA expression after 2 hours cold temperature exposure without the change of Ucn1 peptide content in the EWcp. Partial ablation of the MC3R-MC4R-Ucn1 neurons resulted in lower body temperature in rats reared at neutral external temperature. The same animals exposed to cold temperature showed ineffective adaption mechanism. Based on our results we conclude that Ucn1 neurons carrying both melanocortin 3 and 4 receptors play a complex role in the control of energy homeostasis. In the present study we showed that the body temperature regulation is also affected by the MC3R-MC4R-Ucn1 neurons.