The author examined the role of brainstem noradrenergic (NA) neurons in communicating steroid hormone signals to luteinizing hormone-releasing hormone (LBRH) neurons. To this end, the author tested whether NA neurons contained steroid hormone receptors, whether steroid hormone influenced the activity of NA neurons, whether LHRH neurons or gamma-amino butyric acid (GABA) neurons could receive direct input from NA neurons, and how the GABA system may be influenced by the NA system. Experiment 1 found that progestin receptors were found in numerous nuclei and regions throughout the brainstem, especially in regions containing NA cell groups. Experiment 2 found that estrogen receptor-alpha, estrogen receptor-beta and progestin receptors were found in subpopulations of NA neurons in the ventrolateral medulla (A1 NA neurons) and the nucleus of the solitary tract (A2 NA neurons), as well as in NA neurons in the locus coeruleus (A6 NA neurons). In addition, the author found that a significant number of estrogen receptor-alpha containing neurons in the ventrolateral medulla were GABA neurons. These results suggest that steroid hormones may directly and indirectly regulate NA neurons in the brainstem. Experiment 3 evaluated steroid hormone effects on tyrosine hydroxylase (rate-limiting enzyme for NA synthesis) mRNA levels in A1, A2 and A6 NA neurons. The results demonstrated that subpopulations of NA neurons are activated at different time points on the day of the luteinizing hormone surge. Experiment 4 determined whether alpha1B-, alpha2A- or beta1-adrenergic receptors were found in LHRH neurons or in GABA neurons in the preoptic area. Less than twenty percent of LHRH neurons expressed each adrenergic receptor, whereas 50–80% of GABA neurons expressed each adrenergic receptor. Experiment 5 demonstrated that glutamic acid decarboxylase (GAD) 65 and 67 (synthetic enzymes for GABA) mRNA levels were altered by steroid hormones in the rostral preoptic area/organum vasculosum of the lamina terminalis and the anteroventral periventricular nucleus/media preoptic nucleus. In addition, the changes in GAD 65 mRNA levels parallel changes in tyrosine hydroxylase mRNA levels. Collectively, the results of Experiments 1 to 5 demonstrate the NA communicates steriod hormone signals directly and indirectly to LHRH neurons.
| Identifer | oai:union.ndltd.org:UMASS/oai:scholarworks.umass.edu:dissertations-3497 |
| Date | 01 January 2001 |
| Creators | Curran, Meredith Ames |
| Publisher | ScholarWorks@UMass Amherst |
| Source Sets | University of Massachusetts, Amherst |
| Language | English |
| Detected Language | English |
| Type | text |
| Source | Doctoral Dissertations Available from Proquest |
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