Distribution of adenylate cyclase in the brain of Apteronotus leptorhynchus as revealed by forskolin binding.

Abstract

An antibody directed against an isoform of the rat regulatory subunit of protein kinase A 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 53 kDa) for this enzyme in mammalian cortex and electric fish brain, suggesting that this protein is also found in fish brains. The 53-kDa band was enriched in fish forebrain. [3H]Forskolin binding was used as a marker for the distribution of adenylate cyclase. [3H]Forskolin binding was nearly completely displaced by excess cold forskolin; specific [3H]forskolin binding sites were heterogenously distributed with relatively high densities in some gray matter regions and low densities in fiber tracts. A high density of [3H]forskolin binding sites was found in the dorsal forebrain with lower densities in most ventral forebrain nuclei. Moderate binding densities were observed in the preoptic and hypothalamic areas with the exception of the nucleus tuberis anterior, which had high levels. The thalamus and midbrain had low levels of binding. The cerebellar molecular layer had dense binding, in contrast to the granule cell layer where binding was low. In the electrosensory lateral line lobe (ELL), there was moderate binding in the dorsal and ventral molecular layers, which contain feedback inputs; the cellular layers of the ELL had low binding densities.