GALANIN IMMUNOREACTIVITY IN RAT SPINAL LAMINA-IX - EMPHASIS ON SEXUALLY DIMORPHIC REGIONS

Fibers and puncta that contained galanin-like immunoreactivity (GAL-LI ) were distributed within lamina IX in a heterogeneous fashion. In cer vical spinal segments, GAL-LI was almost absent except for the phrenic nucleus, which received the most robust GAL-LI innervation in lamina IX. In high and mid-thoracic segments. GAL-LI was found in moderate am ounts, but the number of GAL-LI fibers gradually diminished in a cauda l fashion, so that in low thoracic segments GAL-LI was sparse. Through out all thoracic segments, GAL-LI fibers surrounded some clusters of m otoneurons, while other groups of motoneurons were devoid of GAL-LI fi bers. In lumbar segments, three sexually dimorphic nuclei received spa rse to moderate amounts of GAL-LI, while GAL-LI in the remainder of lu mbar lamina IX was very sparse. In sacral spinal segments, GAL-LI was very sparse. These data indicate that fibers and puncta that contain G AL-LI preferentially surround motoneurons that innervate muscles assoc iated with the axial skeleton. while motoneurons that innervate append icular or tail-associated skeletal muscles only have an occasional GAL -LI fiber associated with them.