Alterations in mystacial pad innervation in the aged rat

Area of Science:

• Neuroscience
• Gerontology
• Sensory Biology

Background:

• Sensory perception declines with age, accompanied by axonal dystrophy and degeneration in sensory pathways.
• The mystacial pad, rich in sensory nerve endings, provides a model to study age-related changes in tactile sensation.

Purpose of the Study:

• To investigate the impact of aging on the cutaneous innervation of the rat mystacial pad.
• To identify degenerative and regenerative changes in sensory nerve endings and associated structures in aged rats.

Main Methods:

• Immunohistochemical analysis of mystacial pad specimens from aged (30 months) and young adult (2-3 months) female Sprague-Dawley rats.
• Antibodies used targeted human neuronal cytoplasmic protein (protein gene product 9.5), transmitter enzymes, and neuropeptides including NPY and CGRP.

Main Results:

• Reduced and degenerated Merkel and lanceolate endings from large-caliber afferents; decreased piloneural complexes in aged rats.
• Normal appearance of Ruffini endings and mechanoreceptors from medium-caliber axons.
• Loss of sympathetic NPY/TH-IR and CGRP-IR perivascular axons, with an increase in parasympathetic NPY/CGRP-IR axons.
• Novel fine-caliber axonal networks in whisker follicle root sheaths and de novo NPY presence in CGRP-IR axons in aged rats.

Conclusions:

• Aging induces both degenerative and regenerative changes in mystacial pad innervation.
• Age-related sensory impairments are linked to peripheral processes involving nerve-target interactions and axonal integrity maintenance.
• Specific nerve endings and axonal populations are differentially affected by aging.