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Cholinergic innervation and function in the mammalian pineal gland
P Phansuwan-Pujito1, M Møller, P Govitrapong
1Department of Anatomy, Faculty of Medicine, Srinakharinwirot University, Bangkok 10110, Thailand.
Microscopy Research and Technique
|September 1, 1999
Summary
The mammalian pineal gland has a cholinergic innervation that counterbalances the sympathetic system. This cholinergic system, originating from parasympathetic ganglia, decreases melatonin synthesis by inhibiting N-acetyltransferase activity.
Area of Science:
- Neuroscience
- Endocrinology
- Histology
Background:
- The mammalian pineal gland is primarily known for its sympathetic noradrenergic innervation.
- Evidence for a cholinergic innervation has been accumulating over decades, suggesting a more complex regulatory system.
Purpose of the Study:
- To consolidate and present the evidence for cholinergic innervation of the mammalian pineal gland.
- To elucidate the origin, characteristics, and functional implications of this cholinergic system.
Main Methods:
- Review of historical studies including nerve lesioning and ultrastructural analysis.
- Biochemical assays for enzymes like acetylcholinesterase.
- Modern techniques such as immunohistochemistry, receptor identification, and gene expression analysis.
Main Results:
- Cholinergic nerve fibers and terminals have been identified in the mammalian pineal gland.
- Key enzymes (choline acetyltransferase) and receptors (muscarinic, nicotinic) for acetylcholine have been localized.
- Cholinergic stimulation leads to decreased N-acetyltransferase activity and reduced melatonin synthesis.
Conclusions:
- A functional cholinergic innervation exists in the mammalian pineal gland, originating from peripheral parasympathetic ganglia and potentially central sources.
- This cholinergic system acts antagonistically to the noradrenergic system, playing a crucial role in pineal function homeostasis.
- The findings highlight the intricate neural regulation of melatonin production.