Distribution of protein kinase C in the brain of Apteronotus leptorhynchus as revealed by phorbol ester binding.

An antibody to the mammalian protein kinase C alpha (PKCalpha) subunit and brain dissection was used for immunoblot analysis of this protein in various brain regions of Apteronotus leptorhynchus. Western blots revealed that the antibody labeled a band of the expected molecular mass (approximately 80 kDa) for this enzyme in mammalian cortex and electric fish brain, suggesting that this protein is also found in gymnotiform brain. The 80-kDa band was enriched in fish forebrain and cerebellum compared with hypothalamus and brainstem areas. [3H]Phorbol 12,13-dibutyrate ([3H]PDBu) binding was used as a marker for the distribution of protein kinase C (PKC). [3H]PDBu binding was nearly completely displaced by excess cold PDBu; specific [3H]PDBu binding sites were heterogenously distributed with high densities in some gray matter regions and negligible densities in fiber tracts. A very high density of [3H]PDBu binding sites were found in the dorsal forebrain with far lower densities in most ventral forebrain nuclei. Low binding densities were observed in preoptic and hypothalamic areas with the exception of the nucleus diffusus and nucleus tuberis anterior. The thalamus and midbrain also had only low levels of binding. The cerebellar molecular layer had dense binding, in contrast to the granule cell layer where binding was negligible. In the electrosensory lateral line lobe (ELL), there was moderate binding in the dorsal molecular layer, which contains cerebellar parallel fibers; the other layers of the ELL had far lower binding densities.