Mast cells in the neonate musk shrew brain: implications for neuroendocrine immune interactions.

In allergic and inflammatory conditions, mast cells respond to and affect both the nervous and endocrine systems. Yet, their function in healthy brain tissue is poorly understood. We report here the occurrence of mast cells concentrated in the lateral posterior, laterodorsal and dorsal lateral geniculate nuclei of the thalamus, in the lateral and medial habenula and in overlying pial layers in the brains of neonate musk shrews. Mast cells are very abundant on the day of birth and decline with age. From postnatal day 0 to 9, mast cells are most abundant in the thalamus. The mast cell population declines rapidly in the thalamus after day 9. By postnatal day 15 equivalent numbers of mast cells are seen in the thalamus, lateral and medial habenula. Interestingly, mast cells are in close association with gonadotropin-releasing hormone (GnRH)-containing fibers in the neonate brain suggesting an association between the neuroendocrine and immune systems in the developing musk shrew brain.