The male golden hamster is an important model in which to study the integration of sensory and hormonal signals which control reproductive behavior. In the brain of this species the essential chemosensory pathways and the target sites for testosterone (T), and its metabolites estradiol (E) and dihydrotestosterone (DHT) have been mapped. Neurons in three nuclear areas along these pathways - the medial amygdaloid nucleus (M), the medial bed nucleus of the stria terminalis (BNSTm) and the medial preoptic area (MPOA) - actively accumulate gonadal hormones. The neural connections between these three regions and the influence of gonadal hormones on their neurons are the continuing subject of this project. We have found that T maintains the dendritic arborization of neurons in M and the Substance P production of neurons in M, BNSTm and MPOA. In this proposal, neuronal connections from the rostral to the caudal parts of M are hypothesized to connect regions of this nucleus which differ in their connections, hormone dependence, and behavioral significance. These projections will be studied after iontophoresis of the orthogradely transported tracer Phaseolus vulgaris leucoagglutinin into rostral M and, in other experiments, iontophoresis of the retrogradely transported tracer fluorogold into caudal M. Second, projections made by the hormone-concentrating neurons of M, BNSTm and MPOA will be investigated by combining the injection of retrograde fluorescent tracers (e.g., primuline) with steroid autoradiography. This will double-label hormone-accumulating cells which make specific neuronal connections. Third, the connections of those neurons in M, BNSTm and MPOA which produce Substance P will be studied by immunohistochemical identification of Substance P cells. Last, some specific functions of T and its metabolites in this pathway will be investigated by replacing either T, E, DHT or DHT plus E systemically in castrated males, and comparing the effectiveness of these treatments in maintaining normal dendritic morphology (measured in Golgi preparations) and Substance P production (measured immunohistochemically). Taken together these experiments will further define the neurotransmitter production and hormonal dependence of neurons comprising the mating behavior pathway.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
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Neurology B Subcommittee 2 (NEUB)
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University of Michigan Ann Arbor
Schools of Medicine
Ann Arbor
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Holt, Avril Genene; Newman, Sarah Winans (2004) Distribution of methionine and leucine enkephalin neurons within the social behavior circuitry of the male Syrian hamster brain. Brain Res 1030:28-48
Wood, R I; Newman, S W (1999) Androgen receptor immunoreactivity in the male and female Syrian hamster brain. J Neurobiol 39:359-70
Parfitt, D B; Newman, S W (1998) Fos-immunoreactivity within the extended amygdala is correlated with the onset of sexual satiety. Horm Behav 34:17-29
Kollack-Walker, S; Newman, S W (1997) Mating-induced expression of c-fos in the male Syrian hamster brain: role of experience, pheromones, and ejaculations. J Neurobiol 32:481-501
Newman, S W; Parfitt, D B; Kollack-Walker, S (1997) Mating-induced c-fos expression patterns complement and supplement observations after lesions in the male Syrian hamster brain. Ann N Y Acad Sci 807:239-59
Wood, R I; Bean, A R; Sundaram, K et al. (1996) 7 alpha-methyl-19-nortestosterone facilitates sexual behavior in the male Syrian hamster. Horm Behav 30:131-7
Wood, R I; Newman, S W (1995) Integration of chemosensory and hormonal cues is essential for mating in the male Syrian hamster. J Neurosci 15:7261-9
Kollack-Walker, S; Newman, S W (1995) Mating and agonistic behavior produce different patterns of Fos immunolabeling in the male Syrian hamster brain. Neuroscience 66:721-36
Wood, R I; Newman, S W (1995) Androgen and estrogen receptors coexist within individual neurons in the brain of the Syrian hamster. Neuroendocrinology 62:487-97
Wood, R I; Newman, S W (1995) The medial amygdaloid nucleus and medial preoptic area mediate steroidal control of sexual behavior in the male Syrian hamster. Horm Behav 29:338-53

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