We previously showed that blood acetylcholine(ACh)originates mainly from T−lymphocytes, and that stimulation of muscarinic ACh receptors(mAChRs)induces Ca
2+ oscillations and up−regulates c−fos gene expression in both T− and B−lymphocytes.In the present study, we investigated which mAChR subtypes are involved in Ca
2+ signaling and c−fos gene expression in human T−(CEM)and B−(Daudi)cells.Stimulation of mAChRs with 100μM oxotremorine−M, an M
1/M
3 agonist, increased levels of intracellular free Ca
2+([Ca
2+]
i)and c−fos mRNA expression in both cell lines.4−DAMP, an M
3 antagonist, more effectively blocked the oxotremorine−M−induced increase in [Ca
2+]
i than pirenzepine and telenzepine, M
1−receptor antagonists;AF−DX 116, an M
2 antagonist;hexahydrosiladifenidol, a weak M
3 antagonist;or hexamethonium and d−tubocurarine, nicotinic receptor antagonists.McN−A−343(100μM), a partial M
1−receptor agonist, had no apparent effect on [Ca
2+]
i in either cell line.The oxotremorine−M−induced up−regulation of c−fos transcription was inhibited by 4−DAMP, but not by pirenzepine or AF−DX 116.Our findings thus suggest that ACh released from T−lymphocytes acts as an autocrine/paracrine factor, transmitting a Ca
2+−dependent signal to the nuclei of T− and B−lymphocytes via M
3 receptors.
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