Developmental profile of galanin binding sites in the Mammalian brain.

Galanin (GAL) is a 29-amino acid peptide widely distributed in the mammalian nervous system. Recently, GAL expression has been shown to increase during periods of neuronal degeneration (e.g., Alzheimer's disease) and neuronal injury. Our laboratory has previously reported that GAL immunoreactivity (GAL-IR) is robustly expressed during a time of CNS plasticity, development. The striking GAL-IR seen during times of CNS morphogenesis and neurogenesis led us to the hypothesis that GAL may play a role in the formation of the nervous system. To further substantiate a developmental role for GAL we have used autoradiography to define the distribution of GAL receptors in the forming mammalian brain. To this end, we have used the Brazilian opossum, Monodelphis domestica, as a developmental model. In this study, we have described the profile of GAL receptors in the developing mammalian brain. [(125)I]GAL binding was detected as early as 1 day of postnatal life in regions of the brain which were still undergoing neurogenesis. High levels of GAL receptor expression were region specific and correlated with our previous results on GAL-IR during development. In addition, a transient binding pattern was seen in the anterior pituitary. In the adult brain, the pattern seen was very similar to that of reports in other species. Due to the observations of the presence of GAL and its receptor during times of active neurogenesis and morphogenesis we believe galanin may play an important role in morphogenesis and early functioning of the mammalian CNS.