Distribution of galanin-1, -2 and -3 receptor messenger RNAs in central and peripheral rat tissues.

Galanin is a neuropeptide widely expressed in the central nervous system and periphery. In rat, three galanin-binding receptors have been cloned and characterized. We report the qualitative and quantitative distribution of galanin-1, galanin-2, and galanin-3 messenger RNAs in central and peripheral rat tissues by reverse transcription-polymerase chain reaction and solution hybridization/RNase protection assays, respectively. Galanin-1 messenger RNA was detected exclusively in the central and peripheral nervous system with highest expression in hypothalamus, amygdala, spinal cord and dorsal root ganglia. Galanin-2 messenger RNA was highly expressed in hypothalamus, dorsal root ganglia, and kidney with moderate expression in several other tissues. Galanin-3 messenger RNA was widely distributed at low to moderate levels in many central and peripheral tissues. The observed expression of multiple galanin receptors in several tissues including hypothalamus, anterior pituitary and spinal cord supports earlier pharmacological studies suggesting the presence of more than one receptor subtype in these regions. The presence of multiple galanin receptors in these tissues in conjunction with the detection of a single subtype, galanin-2, in tissues such as heart and intestine, illustrates the potential complexity of galanin-associated actions in rat central nervous system and periphery.