Calcium-dependent pirenzepine-sensitive muscarinic response in the rat hippocampal slice.
Using intracellular recording techniques in the rat hippocampal slice, we observed that muscarinic agonists produce a transient Ca2+-dependent depolarization that may be related to the phosphatidylinositol cycle. First, it was more readily produced by muscarinic group A agonists, which strongly enhance the breakdown of phosphatidylinositol-4,5-bisphosphate (PIP2) than by group B agonists, which are less efficacious. Second, the Ca2+-dependent response was blocked by pirenzepine (PRZ), a selective muscarinic antagonist that blocks PIP2 breakdown in forebrain. Both group A and group B muscarinic agonists caused equivalent maintained levels of depolarization that were relatively insensitive to PRZ. The data suggest that the Ca2+-dependent response is fundamentally unlike other muscarinic responses that have been described in hippocampus.
Pitler
T A
TA
Department of Physiology, University of Maryland School of Medicine, Baltimore 21201.
McCarren
M
M
Alger
B E
BE
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002217:Carbachol / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D010095:Oxotremorine / Q000494:pharmacology; D010277:Parasympathomimetics / Q000494:pharmacology*; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols / Q000378:metabolism; D010890:Pirenzepine / Q000494:pharmacology*; D051381:Rats; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000502:physiology*
D010277:Parasympathomimetics; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols; D011976:Receptors, Muscarinic; D010890:Pirenzepine; D010095:Oxotremorine; D002217:Carbachol; D002118:Calcium