Abstract / Summary
R-spondin 1 (RSPO1) and R-spondin 3 (RSPO3) contribute to reproductive development and feeding regulation, but their hypothalamic glutamatergic regulation remains unclear. We hypothesized that NMDA and non-NMDA receptor mechanisms contribute to hypothalamic RSPO neuronal activation. Given steroid-sensitive hypothalamic glutamatergic signaling, we compared activation and antagonist-mediated attenuation between sexes. Adult male and metestrous female Sprague–Dawley rats received kainic acid or AMPA with or without CNQX pretreatment, or NMDA with or without MK-801 pretreatment. RSPO/c-Fos labeling assessed activation in the supraoptic (SON), paraventricular (PVN), and arcuate (ARC) nuclei; ELISA assessed accompanying changes in serum RSPO concentrations. All agonists activated both populations in all nuclei. Only kainate-induced PVN RSPO3 activation differed between sexes (females, 89.3%; males, 72.8%; unadjusted p = 0.039), an isolated finding among 18 agonist comparisons. Antagonists attenuated all responses, although activation remained above control in 17 of 36 conditions. Females showed greater attenuation in selected kainate and NMDA conditions in the SON and PVN. Serum changes did not parallel neuronal activation. These findings support NMDA and non-NMDA receptor involvement and sex-dependent attenuation of RSPO neuronal activation. Given the central feeding effects of RSPOs, their sex-dependent glutamatergic regulation within neuroendocrine nuclei may contribute to sex differences in metabolic control.