Calcitonin increases 5-HT1A binding site densities in the brain of adrenalectomized rats

Calcitonin is a peptide which acts in the brain to modulate behavior and hormone release, possibly through an interaction with serotonergic systems. We investigated the effects of chronic systemic injections of salmon calcitonin on the [3H]-8-OHDPAT binding to 5-HT1A receptors in the frontal cortex and hippocampus in adrenalectomized and intact (non adrenalectomized) rats. The results show that salmon calcitonin increases the maximal density of 5-HT1A binding sites in both structures in adrenalectomized animals (and decreases the affinity in the frontal cortex only). Calcitonin does not alter this binding in intact rats. These results demonstrate the existence of interactions between calcitonin, serotonin and glucocorticoids, and raise the hypothesis of a neurotrophic effect of calcitonin on serotonergic neurons.