Localization of corticoliberin receptors in the rat brain.

In situ hybridization was used to study the distribution of corticoliberin receptors of subtypes 1 and 2 (CL-R1 and CL-R2 respectively) in different structures of the rat brain. Levels of CL-R1 mRNA in the brain were significantly greater than levels of CL-R2 mRNA, and the most intense expression of the CL-R1 gene was seen in forebrain structures, especially various neocortical, archicortical, and paleocortical regions in the cerebellar cortex. In addition, significant levels of CL-R1 mRNA expression were noted in the red nucleus and the reticular nucleus of the tegmentum. Intense expression of CL-R2 mRNA was observed in structures of the olfactory system, corticomedial parts of the amygdala, fields CA1-CA4 of the hippocampus, the ventromedial hypothalamus, and several brain stem nuclei. Moderate levels of CL-R2 mRNA were seen in the dorsolateral neostriatum. These results provide evidence that corticoliberin receptors of both subtypes are widespread in the brain. The different patterns of expression of CL-R1 and CL-R2 in the brain probably provide the basis for the functional specificity of action of corticoliberin in brain structures.