Irisin is a thermogenic peptide that enables the development of brown adipose tissue from white adipose tissue by activating the UCP1. This study has been designed to determine the effects of the irisin on UCPs. Sprague Dawley female rats were used in the study. 1, 3 and 10 mu M concentrations of irisin were injected intracerebroventricularly to the rats, and the control group was received only vehicle. The animals were killed at the 16, 24, and 48 h time intervals and their brains were taken out. The hypothalamus, pituitary gland, hippocampus, cerebellum, striatum and cortex areas were separated and the UCP2, UCP3, UCP4 and UCP5 mRNA levels were determined. Just before the animals were killed, their body temperatures were recorded.