Patterns of adrenergic and peptidergic innervation in human olfactory mucosa: age-related trends

Abstract

The distribution and targets of nerves containing the adrenergic markers tyrosine hydroxylase, dopamine beta-hydroxylase, and neuropeptide Y in the human olfactory mucosa were investigated by immunohistochemistry. Tissue was obtained at autopsy from the nasal cleft of 16 adults ranging in age from 24 to 90 years, and from one spontaneously aborted 16-week-old fetus. The presence of olfactory receptor neurons in nasal mucosa was confirmed by staining with the antibody to olfactory marker protein. Targets of adrenergic innervation were blood vessels, including the vasa nervorum within the sheaths of olfactory nerve bundles, and Bowman's glands in the lamina propria. Adrenergic fibers penetrated the adventitia of blood vessels and terminated near the media, and were in close proximity to Bowman's glands but did not enter the acini. In the fetal tissue, the vasa nervorum were the major targets of adrenergic fibers. Age-related differences in the pattern and statistically significant differences in the density of innervation of blood vessels were noted between adults under and over 60 years of age. In the younger group, plexuses of nerve fibers containing colocalized dopamine beta-hydroxylase and neuropeptide Y occurred adjacent to arterioles and large bundles of fibers adjacent to venules; in older individuals, few fiber plexuses occurred adjacent to arterioles and thin bundles of fibers adjacent to venules. The distribution of adrenergic innervation suggests that vasomotor tone and secretion are regulated by adrenergic nerves. The decrease in adrenergic innervation in older individuals, with resultant effects on perireceptor processes, may be associated with age-related declines in olfactory function.