Distribution of galanin-like peptide in various tissues of Necturus maculosus

Abstract

Galanin is a biologically active peptide which has a wide pattern of distribution in the mammalian central and peripheral nervous systems. However, the distribution of galanin-like immunoreactivity in amphibian species has not been well elucidated. In the present study, biochemical and immunohistochemical techniques were used to determine the relative concentrations, biochemical nature, and cellular localization of galanin-like immunoreactivity in the brain, heart, urinary bladder, and small intestine of Necturus maculosus (common name: mudpuppy). The results of this study indicate that each of these types of tissue contain a galanin-like peptide which is similar to porcine galanin. Brain and heart concentrations of galanin-like immuno-reactivity were particularly high, although substantial amounts were also present in the small intestine and urinary bladder. Galanin immunoreactivity was observed in ascending fiber tracts of the brainstem and in fibers in the hypothalamus. In addition, galanin immunoreactivity was observed in autonomic neurons and processes in the heart, bladder, and small intestine. The pattern of distribution of galanin-like immunoreactivity in many tissues of this amphibian species is similar to the previously described mammalian pattern; however, galanin-immunoreactive innervation of cardiac tissue has not been reported in mammals. We suggest that galanin-like immunoreactivity in the heart may be more extensive in amphibian species than in mammals.