Involvement of Olfactory Bulb Catecholamines and Luteinizing Hormone-Releasing Hormone in Response to Social Stimuli Mediating Reproductive Functions

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Abstract
In this paper we summarize our findings related to the involvement of olfactory bulb (OB) catecholamines and LHRH in response to social stimuli. Previous work from our laboratory had indicated the presence of LHRH within the OB, with localization of this neuropeptide to the posterior dorsal area of this structure. Subsequent work has demonstrated that the presence and localization of LHRH within the OB is an ubiquitous phenomenon characteristic of several rodent species and appears specific for the neuropeptide LHRH, since TRH failed to demonstrate any comparable localization. Analysis of catecholamine concentrations by HPLC-EC revealed that norepinephrine was present in greatest concentrations. Changes in the concentration of LHRH within the OB were obtained following social or chemical cue stimulation. These changes were also localized to the posterior OB, appeared to be specific for LHRH (versus TRH) and were associated with changes in catecholamine concentrations. Recently, we have implanted a push-pull cannula in the OB of male rats and measured the in vivo release of these neuroactive substances in the awake freely moving rat. Release of LHRH from the OB was extremely low with most samples below the detectability of the assay. When detectable, the output of LHRH did not appear to be associated with the introduction of a receptive female. In contrast, norepinephrine output was obtained from all males and demonstrated marked increases in response to the introduction of a receptive female, suggesting that this neurotransmitter may be an important component for processing chemical cue information within the OB.