Galanin synaptic input to gonadotropin-releasing hormone perikarya in juvenile and adult female mice: implications for sexual maturity

Changes in connectivity of the gonadotropin-releasing hormone (GnRH) neuron al system are believed to occur during the transition from juvenile to adul thood in females. Experiments were designed to investigate whether there is any difference in the number of galanin inputs to GnRH cells located in th e organum vasculosum of lamina terminalis-rostral preoptic area (OVLT-rPOA) between juvenile (2 weeks old) and adult (10 weeks old) female mice. Tripl e label immunofluorescence staining of brain sections for galanin, GnRH and the presynaptic vesicle marker synaptophysin coupled with confocal microsc opy was employed to identify galanin synapses to GnRH perikarya. The number of galanin synapses to GnRH cells and the proportion of GnRH cells with ga lanin input were significantly higher in adults than in juvenile mice. In a dult mice, the proportions of GnRH cells with 0, 1, 2, 3, 4, 5 or 6 galanin synapses/cell were comparable to each other whereas in the juveniles the v ast majority of them received no galanin synaptic input. A greater number o f galanin synapses in adult as compared with juvenile female mice suggests a functional role for galanin in the maturation of the GnRH system. (C) 200 1 Elsevier Science B.V. All rights reserved.