Muscarinic activation reduces changes in [Ca2+]o evoked by stimulation of Schaffer collaterals during blocked synaptic transmission in rat hippocampal slices.
The rat hippocampal slice preparation and blockers of postsynaptic glutamate receptors (6-nitro-7-sulphamoylbenzo(f)quinoxaline-2,3-dione (NBQX) 10 microM; DL-2-amino-5-phosphonovaleric acid (APV) 30 microM) were used to study the effects of muscarinic activation on stimulus-induced decreases in [Ca2+]o presumably due to presynaptic Ca-influx. Perfusion with carbachol (100-200 microM) transiently reduced these changes in [Ca2+]o. Blockade of this muscarinic effect by pirenzepine (200 microM) and prolongation of this effect after prolonged lithium (1 mM) incubation suggest involvement of the muscarinic M1 receptor subtype. These findings suggest, that activation of M1 receptors might contribute to inhibition of excitatory synaptic transmission by inhibiting presynaptic Ca-influx. In this way, the muscarinic enhancement of excitatory input may be limited to non-deleterious levels.
Egorov
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AV
AG Molekulare Zellphysiologie, Institut für Physiologie der Charité, Humboldt Universität zu Berlin, Germany.
Heinemann
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U
Müller
W
W
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D004558:Electric Stimulation; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D018721:Muscarinic Agonists / Q000494:pharmacology*; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D017661:Receptors, Presynaptic / Q000187:drug effects; D009435:Synaptic Transmission / Q000187:drug effects*
D018691:Excitatory Amino Acid Antagonists; D018721:Muscarinic Agonists; D011810:Quinoxalines; D017661:Receptors, Presynaptic; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; D015763:2-Amino-5-phosphonovalerate; D002217:Carbachol; D002118:Calcium