Abstract
Abstract: In vitro studies with cultured cells originating from nervous tissue have shown that chronic exposure to muscarinic agonists results in a loss of muscarinic receptors. To determine whether this type of regulation of muscarinic receptor number also occurs in vivo, we infused carbachol into the spinal cords of rats. A single carbachol injection into the lumbar spinal cord caused a significant increase in the nociceptive threshold. This effect of carbachol diminished to control levels after 12 h of repeated agonist injections every 4 h and was blocked by atropine. The desensitization to the antinociceptive effects of carbachol was associated with a loss of muscarinic receptors as determined by the binding of the muscarinic antagonist [3H]quinuclidinyl benzilate. After a 24‐h exposure to carbachol given every 4 h, there was about a 60% loss of binding sites. The loss of muscarinic receptors was also blocked by atropine and was reversible. These results represent direct evidence that a muscarinic agonist can regulate receptor number in the central nervous system and suggest that this loss of receptors is associated with a desensitization to the antinociceptive effects of carbachol injected into the spinal cord.
Original language | English (US) |
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Pages (from-to) | 521-524 |
Number of pages | 4 |
Journal | Journal of neurochemistry |
Volume | 39 |
Issue number | 2 |
DOIs | |
State | Published - Aug 1982 |
Keywords
- Agonists
- Muscarinic
- Receptors
- Regulation
ASJC Scopus subject areas
- Biochemistry
- Cellular and Molecular Neuroscience