Brain distribution of four rat homologues of the Drosophila dunce cAMP phosphodiesterase.

We have analyzed the brain distribution of the rat cAMP-specific phosphodiesterases (rPDEIV) which are closely related to the defective gene products of the drosophila melanogaster learning and memory mutant dunce. PCR analysis of rat brain cDNA was performed on the four known dunce-like cAMP PDE rat isogenes (rPDE-IV-A, -B, -C, -D). High expression of three of these isogenes (rPDEIV-A, -B, -D) highlighted their involvement in regulation of cAMP in the brain. Specific probes for all four isogenes were then used for in situ hybridization of rat brain sections. Distinct but overlapping expression patterns were observed for rPDEIV-A, rPDEIV-B, and rPDEIV-D. Abundant expression of these subtypes was observed in the olfactory system, the hippocampus and the cerebellum, while no specific signals could be detected in most areas of the brain for the subtype rPDEIV-C.