Distribution of target cells for 1,25-dihydroxyvitamin D 3 in the brain of the yellow bellied turtle Trachemys scripta

Abstract

Five h after injection of tritiated 1,25-dihydroxyvitamin D 3 into Trachemys scripta, neurons with nuclear concentrations of radioactivity were identified in distinct regions within the central nervous system. Coinjection of a 100-fold excess of non-labeled 1,25-dihyroxyvitamin D 3 abolished or reduced the specific nuclear binding of tracer. Target neurons were present in ventral periventricular brain regions including tuberculum olfactorium, nucleus accumbens, cortex piriformis, primordium hippocampi, nucleus striae terminalis, dorsal ventricular ridge, amygdala, nucleus infundibularis and tectum opticum. With the exception of the nucleus infundibularis and the tectum opticum, target neurons can be continuously followed from the ventrolateral nucleus accumbens throughout the nucleus striae terminalis into the amygdala. The general distribution of target neurons is similar to that described for rodents but more restricted to the above regions. The results show that target neurons for vitamin D are located in brain regions including several components of the limbic and thalamic systems in which gonadal steroids as well as aminergic and peptidergic messengers exert their actions. Vitamin D, the heliogenic steroid hormone, may therefore be involved in the orchestration of season-specific processes such as reproduction and related behaviors.