Luteinizing hormone-releasing hormone in olfactory bulbs of primates

This immunohistochemical study of luteinizing hormone‐releasing hormone (LHRH) in the olfactory bulbs in primates was undertaken in order to see whether there was an LHRH innervation in these species similar to that found in rodents. One old world (Macaca fascicularis) and two new world (Saimiri sciureus and Aotus trivirgatus) monkeys were studied. Aotus trivirgatus was of particular interest as it is noctural and so presumably more dependent upon olfactory cues. Animals were perfused with fixative, olfactory bulbs removed and sectioned, and tissues reacted immunocytochemically using LR1 (Benoit) antiserum to LHRH. Some LHRH innervation was found in the olfactory bulbs of all three species, comprising a few LHRH neurons and many fibers that ramified within the bulbs. The accessory bulb (not present as a distinct entity in old world primates) had more LHRH innervation than did the main olfactory bulb. Aotus trivirgatus had the greatest representation of LHRH of the three species. The layer of the olfactory bulb with the greatest number of LHRH fibers was the external plexiform layer. This is also true in rodents. There is evidence that LHRH has a role in the mediation of olfactory cues in reproductive behavior in rodents. It is not known how LHRH functions within the olfactory system in primates. However, the fact that it is distributed similarly in the two groups suggests that it may serve a similar function.