The development of galanin-like immunoreactivity in the rat central nervous system has been investigated immunologically. Galanin-positive processes in the central nervous system were first recognized at day 1 post-natal, in the dorsal horn of the spinal cord. At day 2, the first galanin-immunoreactive neuronal somata were visualized in several regions of the diencephalon; at later stages of maturation positive cells were also detected in many brain stem areas. The number, density and staining intensity of galanin-positive structures in these and other regions increased steadily until day 28, by which age the adult disposition was attained. Increases in the concentrations of galanin-like immunoreactivity during maturation of the animals closely paralleled the immunohistochemical findings. No reduction in galanin-like immunoreactivity was noted in any area during later post-natal ages. The present study indicates that the ontogeny of galanin-like immunoreactivity in the rat central nervous system occurs entirely post-natally. The developmental profile is consistent with the role of galanin as a putative neurotransmitter/neuromodulator in the rat brain and spinal cord.

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