The sympathetic division of the autonomic nervous system is known to play a role in the genesis of neuropathic pain. In the skin of the rat lower lip (hairy skin), sympathetic and parasympathetic fibres normally innervate the same blood vessels in the lower dermis but do not occur in the upper dermis. However, we have shown that sympathetic fibre migration into the upper dermis occurs following mental nerve lesions (1. Compo Neurol. 422:287-296, 2000). As sensory denervation has a dramatic effect on sympathetic fibre innervation patterns in the rat lower lip skin, we decided to investigate the possible changes in the other autonomic fibre type in the skin - the parasympathetic fibre. Sensory denervation of the rat lower lip was achieved by bilateral transection of the mental nerve, and animals were allowed to recover for one to eight weeks. Lower lip tissue was processed for double labelling light microscopic immunocytochemistry (ICC), using antibodies against substance P (SP), which labels a subpopulation of peptidergic sensory fibres, and against the vesicular acetycholine transporter (VAChT), used as a marker for parasympathetic fibres. In sham-operated rat, SP-immunoreactive (IR) sensory fibres were found in the epidermis and upper and lower dermal regions, whereas VAChT-IR fibres were confined to the lower dermis. Mental nerve lesions induced the gradual disappearance of SP-IR fibres from all skin layers accompanied by the progressive migration of VAChT-IR fibres into the upper dermis. Cholinergic fibre migration was evident by the second week post-surgery and the ectopic innervation of the upper dermis by these fibres persisted even at the last time point studied (8 weeks). VAChT-IR fibres were observed in the upper dermis, well above the opening of the sebaceous glands into the hair follicles. These results show that considerable changes occur in the innervation patterns of parasympathetic fibres following mental nerve lesions. The unique cutaneous innervation of the trigeminal region - sensory, sympathetic, and parasympathetic - presents novel opportunities for close interactions between these three fibre types and may have implications for improving the existing understanding and treatment of neuropathic pain in this region.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.19426 |
| Date | January 2003 |
| Creators | Ramien, Michele |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Pharmacology & Therapeutics) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 002010118, Theses scanned by McGill Library. |
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