PROPORTIONS OF RENAL AND SPLENIC POSTGANGLIONIC SYMPATHETIC POPULATIONS CONTAINING GALANIN AND DOPAMINE-BETA-HYDROXYLASE

Galanin is a 29-amino acid neuropeptide found in rat spinal cord, auto nomic ganglia and gastrointestinal tract, as well as in other areas of the nervous system in rats and other species. As part of an overall o bjective to determine if peptides contribute to target-specific contro l of visceral function, this study was designed to determine the perce ntages of populations of renal and splenic postganglionic neurons that contain galanin, and to determine if these neurons were likely to be adrenergic. Retrogradely transported fluorescent dyes were placed on r enal and splenic nerves in male Wistar rats anaesthetized with sodium pento-barbital. Four days post-operatively, rats were perfused transca rdially with fixative, and T12-L1 thoracolumbar chain ganglia, splanch nic ganglia and the solar pl''us were removed. Immunocytochemical meth ods were then used to determine the proportions of the retrogradely la belled renal and splenic neurons containing galanin-like immunoreactiv ity and dopamine beta hydroxylase-like immunoreactivity. In seven rats , 24 +/- 3% of 2838 renal neurons were found to contain galanin-like i mmunoreactivity; in six rats, 32 +/- 5% of 5102 splenic neurons were f ound to contain galanin-like immunoreactivity. These proportions of th e two populations were not significantly different from one another. I n three rats, 94 +/- 2% of 684 renal neurons were found to contain dop amine beta hydroxylase-like immunoreactivity, and 95 +/- 2% of 2597 sp lenic neurons in three rats also showed dopamine beta hydroxylase-like immunoreactivity. These experiments indicate that subpopulations of b oth renal and splenic postganglionic sympathetic neurons contain the n europeptide galanin and that these neurons are likely to be adrenergic in function. These findings suggest a role for galanin in control of the kidney and the spleen by the sympathetic nervous system.