We have recently isolated a cDNA encoding a short isoform of the corticotropin-releasing factor (CRF) receptor subtype, referred to as CRF(2)alpha -tr, from the rat amygdala. The present study determined the localization of the truncated receptor mRNA in the rat brain by in situ hybridization histochemistry. The results showed significant levels of hybridization in the lateral septum, central nucleus of the amygdala, cortico-amygdaloid nucleus, ventrornedial nucleus of the hypothalamus (VMH), and frontal cortex. In the physiological study, antidepressive drugs increased the expression of CRF(2)alpha -tr mRNA and the total binding activity to CRF in the rat amygdala. These findings suggest that CRF(2)alpha -tr may regulate endogeneous CRF release in the amygdala.