Physiological evidence of an inverse correlation between the gonadal function and rfrp-3 neurons in mice

Abstract

The temporal phase relation of circadian neural oscillations (serotonergic and dopaminergic) are reported to account for seasonal physiological conditions including reproduction. The circadian rhythms of hormones (corticosterone and prolactin) appear to be important expression of these oscillations and by feed-back mechanism hormonal rhythms may not only maintain the neural oscillations (serotonergic and dopaminergic) but may also entrain each other. Further, in this direction and on the assumption/evidence that hormonal rhythms are the expression of neural rhythms, 5-hydroxytryptophan (5-HTP), a rate limiting precursor substrate for serotonin, was substituted for corticosterone, and L-dihydroxyphenyalanine (L-DOPA), a rate-limiting precursor for dopamine, was substituted for prolactin. Although so far most of the studies have concentrated on the serotonergic and dopaminergic oscillations possibly due to their central effect, role of other oscillations cannot be ruled out. Our study presented in this communication deals with the temporal phase relation between two neural oscillations (serotonergic and dopaminergic) that are conveyed to regulate seasonal reproductive and other metabolic/physiological conditions. Our work tested the applicability of this mechanism in continuous breeder Parkes (P) strain mice during postnatal gonadal development and attainment of puberty with respect to the expression of a hypothalamic gonadotropin-inhibitory peptide, RFamide-related peptide-3 (RFRP-3). Further, age-dependent variations were also monitored in the expression of ir- RFRP-3 in mice brain and the testicular activity to assess the possible correlation between the gonadal function (development, maturation and regression).