Pituitary adenylate cyclase activating peptide (PACAP) mRNA in the rat neocortex

In agreement with previous studies, Northern blots revealed expression of pituitary adenylate cyclase-activating peptide (PACAP) mRNA in the rat cerebral cortex. In order to identify the cells expressing PACAP mRNA, semiquantitative in situ hybridization histochemistry was applied. A moderate concentration of PACAP mRNA transcripts was determined in the cingulate and frontal cortices, whereas lower concentrations were found in other cortical areas. In emulsion dipped sections, grains were detected over cell bodies in cortical layers II, III and IV. Grains were diffusely distributed over cells in the outer granular layer of the anterior cingulate and the retrosplenial areas. In the outer pyramidal cell layer a few neurons contained a large number of grains. These data show that PACAP mRNA is present in cells outside the hypothalamus and implies that PACAP could play a broader transmitter role in the CNS than earlier anticipated.