Vitamin D target systems in the brain of the green lizard Anolis carolinensis

Autoradiographic mapping criteria were employed to identify and localize specific high affinity binding sites (receptors) for the steroid hormone 1,25-dihydroxyvitamin D3 (1,25-D3) in the brain of Anolis carolinensis. In female and male lizards binding of tritiated 1,25-D3 occurred in identical regions of the fore-, mid-, and hindbrain, similar to findings in other species. There was a band of intensely labeled neurons forming a continuum from the n. accumbens, n. striae terminalis, the striatum, and extending into the amygdala. Target areas with high to intermediate labeling intensities were present in many other regions of the brain and single, small target cells were found throughout the organ. Some cells in the pituitary and pineal were labeled and also cells associated with the meninges, choroid plexuses and ependyma. The differential labeling suggests the existence of different 1,25-D3-responsive systems. One of the conspicuous "high capacity-high affinity systems" is found in the n. accumbens-n. striae terminalis and the amygdala. Most of the cerebral target regions for vitamin D correspond to those known for gonadal steroids, and the seasonal steroid 1,25-D3 may therefore act in conjunction with gonadal steroids in this seasonally breeding reptile.