Differential enhancement by potassium ions of M1-type and M2-type muscarinic receptor-mediated phosphoinositide breakdown in the rat brain.
Raising the assay [K+] from 6 to 18 mM enhances the inositol phospholipid breakdown response to carbachol in rat brain miniprisms. In the frontal cortex, the degree of enhancement by K+ was independent of the carbachol concentration used, whereas in the striatum, a significantly higher degree of enhancement was seen at 1000 than at 50 microM carbachol. The carbachol-stimulated inositol phospholipid breakdown was antagonized by pirenzepine at both [K+] with potencies suggesting involvement of M1-type muscarinic receptors in the frontal cortex and both M1- and M2-type muscarinic receptors in the striatum. It is suggested that the response mediated by the M1-type receptors is enhanced to a greater degree by raised [K+] than that mediated by the M2-type receptors.
Tiger
G
G
Department of Pharmacology, University of Umeå, Sweden.
Björklund
P E
PE
Fowler
C J
CJ
D000818:Animals; D002217:Carbachol / Q000494:pharmacology*; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D005625:Frontal Lobe / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010716:Phosphatidylinositols / Q000378:metabolism*; D010890:Pirenzepine / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology*; D051381:Rats; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000502:physiology*
D010716:Phosphatidylinositols; D011976:Receptors, Muscarinic; D010890:Pirenzepine; D002217:Carbachol; D011188:Potassium