M1 muscarinic receptor-induced facilitation of ACh and noradrenaline release in the rat bladder is mediated by protein kinase C.
1. [3H]Noradrenaline (NA) AND [14C]acetylcholine (ACh) released by electrical field stimulation were measured simultaneously in strips from the body of rat urinary bladder. 2. [3H]NA and [14C]ACh release was greater during continuous stimulation (CS; 10 Hz, 100 shocks) or in the presence of eserine than during intermittent train stimulation (IS; 10 Hz, 10 shocks every 5 s, 10 times). Atropine (1 microM) or pirenzepine (0.05-0.1 microM) blocked the CS- or eserine-facilitated release. 3. The protein kinase C (PKC) activator phorbol dibutyrate (PDB; 0.05 and 0.5 microM) increased the release of both [3H]NA and [14C]ACh in a concentration-dependent manner. Atropine blocked the PDB-induced facilitation of ACh release but not the facilitation of NA release. 4. The protein kinase A (PKA) activator 8-Br-cAMP did not affect ACh release but enhanced NA release. 5. The PKC inhibitor H-7 (50-100 microM) inhibited the CS- or eserine-facilitated release of both ACh and NA, but did not affect the non-facilitated release evoked by IS. H-7 also inhibited 0.5 microM PDB-induced facilitation of ACh release but not NA release. 6. Down-regulating PKC by pretreatment for 30 min with 5 microM PDB decreased the facilitated release of ACh and the eserine-induced facilitation of NA release. 7. Electrically evoked contractions of the bladder strips exhibited a biphasic response to PDB (2.5 microM), which consisted of an initial enhancement of the peak amplitude and area followed after 20 min by an inhibition of contractions. H-7 inhibited the electrically evoked contractions in a dose-dependent fashion. 8. It is concluded that a phospholipase C-PKC signal transduction pathway is essential for muscarinic receptor-induced facilitation of ACh and NA release but is not involved in the non-facilitated release of transmitters in the rat urinary bladder.
Department of Pharmacology, University of Pittsburgh, PA 15261, USA. somo+@pitt.edu
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Somogyi
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Tanowitz
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de Groat
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D017776:Autonomic Pathways / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008297:Male; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009411:Nerve Endings / Q000187:drug effects / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism*; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000502:physiology*; D015290:Second Messenger Systems / Q000187:drug effects / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D001743:Urinary Bladder / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*
D018727:Muscarinic Antagonists; D011976:Receptors, Muscarinic; D015240:Phorbol 12,13-Dibutyrate; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D000109:Acetylcholine; D009638:Norepinephrine