Cold exposure activates Thyrotropin Releasing Hormone (TRH)-producing neurons in specific brain nuclei

SPRING VALDIVIA; AGUSTINA CABRAL; MIRTA REYNALDO; SILVIA GORDON; YAMILA QUIROGA; EDUARDO A. NILLNI; MARIO PERELLO

Congreso; XXVI Congreso Anual de la Sociedad Argentina de Investigación en Neurociencia; 2011

  TRH mediates cold-induced thermogenesis via both neuroendocrine and autonomic mechanisms. It is known that the TRH neurons located in the hypothalamic paraventricular nucleus (PVN) regulate the neuroendocrine thyroid axis. In contrast, what populations of TRH neurons mediate the activation of the sympathetic mechanisms induced by cold exposure is unclear. Here, we systematically examined the distribution of TRH neurons activated in response to cold exposure throughout the adult rat brain. To map the activation TRH neurons, we used double immunohistochemistry for the marker of cellular activation, cfos, and the TRH prohormone. To further assess the functional consequences of the cfos expression in TRH neurons, we evaluated the preproTRH mRNA levels in brain micro-dissections where TRH is produced. Our analysis was focused on hypothalamic regions including the PVN, the pre-optic area, dorsomedial nucleus and the lateral hypothalamus, and areas of the medulla including raphe obscurus, raphe pallidus (RPa) and parapyramidal regions. Our data indicated that only the TRH neurons located in the PVN and the RPa are activated in animals exposed to cold. Thus, these groups of TRH neurons are the main candidates participating in cold-induced thermogenic mechanisms.