Effects of microinjection of melatonin into various brain regions of Japanese quail on locomotor activity and body temperature

We previously reported that peripheral administration of melatonin resulted in simultaneous decreases in locomotor activity and body temperature in the Japanese quail. To examine the site of these melatonin-induced effects, we performed microinjection of melatonin into various brain regions of the Japanese quail. On the basis of the injection site the effects of melatonin were dissociated into four groups: decrease in only body temperature, decrease in only locomotor activity, decrease in both body temperature and locomotor activity, and a change in neither. The decrease in only body temperature was observed when melatonin was injected into areas of the diencephalon including the thalamus and hypothalamus, and the decrease in only locomotor activity was observed when melatonin was injected close to the nuclei septalis medialis and septalis lateralis. These results suggest that melatonin-induced decreases in body temperature and locomotor activity occur by melatonin acting at discrete sites in the brain.