GLIAL ENSHEATHMENT OF GNRH NEURONS IN PUBERTAL FEMALE RHESUS MACAQUES

During the period of development, prior to full sexual maturity, gonad otropin hormone-releasing hormone (GnRH) neurons are fully capable of synthesizing and processing the GnRH decapeptide. Nonetheless, the sec retion of the hormone is not adequate to stimulate adult patterns of g onadotropin release. The present study was undertaken to examine ultra structural characteristics of the GnRH neuron and its relationship to its environment in early- midpubertal female rhesus monkey. These neur ons bore all the ultrastructural immunocytochemical characteristics of those in mature animals, but quantitative morphometrics revealed that they were extensively apposed by glial processes. Such ensheathment w as described earlier in ovariectomized adult animals and was found to be reversible by administration of gonadal steroids. The density of sy naptic input th GnRH neurons in the pubertal animals did not differ si gnificantly from that of adult intact or ovariectomized animals from a previous study. Chemical identification will be required to determine whether there are age or hormonal differences in the innervation of t hese neurons. These results provide anatomical evidence in support of indications from other studies that the ovarian steroidal milieu affec ts GnRH-glial relationships. Further testing will be required to deter mine whether the attainment of sexual maturity in the female rhesus ma caque is dependent upon a reduction in glial ensheathment of GnRH neur ons.