Cholecystokinin-8-like immunoreactivity is sexually dimorphic in a midline population of rat lumbar neurons.

The gray matter surrounding the central canal of rat lumbar spinal cord contains a population of spinothalamic neurons which has been shown to co-contain cholecystokinin-8 (CCK-8) and galanin (GAL) (Ju, G., Melander, T., Hökfelt, T. and Frey, P., Immunohistochemical evidence for a spinothalamic pathway co-containing cholecystokinin- and galanin-like immunoreactivities in the rat. Neuroscience, 20 (1987) 439-456). A previous study from our laboratory has shown that female rats have only 62% the number of GAL-containing midline neurons present in males. Counts of CCK-8-containing midline neurons reveal that females have 59% the number observed in males. These results indicate that the degree of sexual dimorphism seen for CCK-8 is the same for GAL in these midline lumbar neurons, and suggests that androgens modulate the production of the co-contained GAL and CCK-8 in a similar fashion within male rat spinal cords.