Differential distribution of cAMP-specific phosphodiesterase 7A mRNA in rat brain and peripheral organs

We investigated the regional distribution and cellular localization of mRNA coding for the cAMP-specific phosphodiesterase 7A (PDE7A) in rat brain and several peripheral organs by in situ hybridization histochemistry. The reg ional expres sion of two splice variants, PDE7A1 and PDE7A2, was examined b y RT-PCR using RNA extracted from several brain regions. PDE7A mRNA was fou nd to be widely distributed in rat brain in both neuronal and nonneuronal c ell populations. The highest levels of hybridization were observed in the o lfactory bulb, olfactory tubercle, hippocampus, cerebellum, medial habenula nucleus, pineal gland, area postrema, and choroid plexus. Positive hybridi zation signals were also detected in other areas, such as raphe nuclei, tem poral and entorhinal cortex, pontine nuclei, and some cranial nerve motor n uclei. Both mRNA splice forms were differentially distributed in several ar eas of the brain with the striatum expressing only PDE7A1 and the olfactory bulb and spinal cord expressing PDE7A2 exclusively. In peripheral organs t he highest levels of PDE7A hybridization were seen in kidney medulla, altho ugh testis, liver, adrenal glands, thymus, and spleen also presented high h ybridization signal. These results are consistent with PDE7A being involved in the regulation of cAMP signaling in many brain functions. The consisten t colocalization with PDE4 mRNAs suggests that PDE7A could have an effect o n memory, depression, and emesis. The results offer clear anatomical and fu nctional systems in which to investigate future specific PDE7 inhibitors. S ynapse 40:201-214, 2001. (C) 2001 Wiley-Liss, Inc.