大脑皮层M受体亚型及功能

THE MUSCARINIC RECEPTOR SUBTYPES IN CEREBRAL CORTEX AND THEIR FUNCTIONS

Radioligand binding experiments using 8H-QNB and 8H-PZ were performed on the cortex and hippocampus and the cerebellum of Wistar rat brains.It was found that the M1 receptor accounted for approximately 90% the total muscar-inic receptors in the cortex and hippocmpus,and M2 accounted for only about 10 %.When separate scopolamine,atropine,pirenzepine and AF-DX 116 were added to compete against the 8H-labelled reagents in binding to the receptors in the two parts of brain,the pki values obtained suggest that the affinity of scopolamine for M1 is higher than for M2 receptors,and the affinity of atropine for M2 is higher than for M1.In the conscious rabbits with preset electrodes, EEG was recorded and motor activities were observed. When pilocarpine was given, excitatory effects were observed on EEG and motor activities.When 8310 was given,the effects were inhibitory.These results, however,were reversed when M1 and M2 receptors were blocked by adding PZ and AF-DX 116 separately.Thus it can be seen that scopolamine inhibits the EEG and motor activities by blocking the M1 receptor,while the excitatory effect of atropine is brought about by blocking the M2 receptor.