Medial diencephalic sites involved in calcitonin-induced hyperthermia and analgesia

Calcitonin is a peptide hormone which can act centrally to decrease food intake and locomotor activity, and increase body temperature and nociceptive thresholds. In a previous study we showed that the brain sites involved in the food intake and locomotion decreases were mostly the paraventricular nucleus, the perifornical area and the preoptic area above the optic chiasma. We now study the diencephalic sites involved in calcitonin-induced increases in body temperature and nociceptive thresholds. Salmon calcitonin (15 ng in 0.3 microliters) was injected in several diencephalic sites, and the effects on body temperature and nociceptive thresholds compared with a saline injection. The results show that the sensitive sites are the dorsomedial nucleus of the hypothalamus, the preoptic area and the centromedial nucleus of the thalamus, and not the paraventricular nucleus and adjacent perifornical area. Therefore, different kinds of central effects of calcitonin can be differentiated on an anatomical basis.