Ultrastructral evidence suggests variations in biosynthesis and processing within LH-RH neurons as a function of ovariectomy in rats

Abstract

We have demonstrated that populations of luteinizing hormone-releasing hormone (LH-RH)-immunopositive neuronal perikarya change following gonadectomy of male and female rats in a sex-dependent manner related to rises in plasma luteinizing hormone (LH). In this study we characterize the ultrastructural state of organelles involved in protein synthesis, primarily within perikarya of rostral preoptic area LH-RH neurons surrounding the organum vasculosum of the lamina terminalis (OVLT). One day following ovariectomy little rough endoplasmic reticulum (RER) was evident, however, the cisternae were heavily laden with ribosomes and numerous polysomes were present free in the cytoplasm. Six days and 3 weeks post-ovariectomy the cisternae of RER were progressively more abundant and dilated; the multiple Golgi apparati, located in close proximity to the RER, were composed of many lamellae and extensive associated vesicles. We propose that increased pools of messenger ribonucleic acid (mRNA) are generated by 1 day post-ovariectomy prior to increased synthesis of precursor, 6 days and 3 weeks post-ovariectomy. Axodendritic synaptic profiles in the neuropil surrounding LH-RH perikarya increased in number in the rostral medial preoptic area and lateral anterior hypothalamic area. We conclude that removal of gonadal steroids results in greater biosynthetic activity in LH-RH neurons, and suggest that the enhanced biosynthesis is related to increases in afferent activity.