EXPRESSION OF CONNEXIN43 MESSENGER-RNA IN ADULT RODENT BRAIN

The expression of connexin43 mRNA was detected in adult rat brains by in situ hybridization methods. Specific digoxigenin riboprobes were ge nerated by in vitro transcription of two PCR-amplified fragments of co nnexin43 cDNA which lack homology with any other published connexin. F ollowing immunohistochemical detection, the digoxigenin cRNA was found to occur in various neuronal populations including Purkinje cells of the cerebellum, pyramidal cells of the neocortex and the hippocampal f ormation, as well as granule cells of the dentate gyrus and various ne urons of diverse hindbrain nuclei. This ubiquituous expression of conn exin43 mRNA in adult neurons, in particular in neocortical pyramidal c ells, is surprising insofar as gap junction communication in adult bai ns has been considered to be confined to specific subpopulations of ne urons revealing a high incidence of synchronized electrical activities in contrast to the postnatal brain where interneuronal coupling via g ap junctions precedes the formation of chemical transmission. In addit ion, connexin43 is regarded as being preferentially expressed in astro cytes, although its presence in adult neurons has not definitely been excluded. We propose that adult neurons preserve their capability of e xpressing functional gap junctions more frequently than presently cons idered and that connexin43 is a most likely neuronal gap junction prot ein candidate.