Postmortem changes in binding to the muscarinic receptor from human cerebral cortex

Area of Science:

• Neuroscience
• Pharmacology
• Biochemistry

Background:

• Muscarinic acetylcholine receptors (mAChRs) are critical in the central nervous system.
• Accurate measurement of receptor binding properties is essential for pharmacological research.
• Tissue storage conditions can impact receptor integrity and binding characteristics.

Purpose of the Study:

• To investigate the stability of muscarinic acetylcholine receptor binding sites and affinities.
• To evaluate the effects of 4°C storage on both antagonist and agonist binding.
• To compare receptor properties in fresh surgical versus frozen autopsy human cerebral cortex samples.

Main Methods:

• Radioligand binding assays using L-[3H]3-quinuclidinyl benzilate (QNB).
• Measurement of antagonist binding site density and affinity.
• Assessment of agonist (carbachol) competition for antagonist binding.
• Tissue storage as intact pieces versus homogenate at 4°C for up to 51 hours.

Main Results:

• The number and affinity of L-[3H]3-quinuclidinyl benzilate binding sites remained stable up to 51 hours in both intact tissue pieces and homogenates.
• Agonist (carbachol) binding properties were stable in intact tissue pieces but decreased in homogenates.
• Frozen autopsy samples exhibited no significant differences in binding properties compared to fresh surgical tissue.

Conclusions:

• Human cerebral cortex muscarinic acetylcholine receptors maintain stable antagonist binding properties at 4°C for at least 51 hours in both intact tissue and homogenates.
• Agonist binding stability is maintained in intact tissue but compromised in homogenates under these storage conditions.
• Frozen autopsy tissue is a viable alternative to fresh surgical tissue for studying muscarinic receptor binding characteristics.