title: Interactions between inhibitory and excitatory modulatory signals in single submucosal neurons.
abstract: Intracellular recordings were made in submucosal neurons from the guinea pig ileum to study the actions of norepinephrine and somatostatin on slow depolarizations induced by 2-chloroadenosine (CADO) and substance P. Local application (by pressure) of CADO and substance P induced a slow depolarization that occurred concomitantly with an increase in input membrane resistance. Norepinephrine, UK-14304 (alpha 2-adrenoceptor agonist), and somatostatin blocked the excitatory responses induced by CADO in a concentration-dependent manner. The alpha 2-adrenoceptor antagonists idazoxan and yohimbine antagonized these inhibitory effects of UK-14304 and norepinephrine. UK-14304 also decreased depolarizations induced by forskolin, but not those induced by the adenosine 3',5'-cyclic monophosphate analogue 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate. Slow depolarizations induced by substance P were blocked neither by UK-14304 nor by somatostatin. It was previously shown that staurosporine (an inhibitor of various protein kinases) and KT-5720 (an inhibitor of protein kinase A) inhibited slow depolarizations induced by CADO. Here, substance P depolarizations were inhibited by staurosporine and calphostin C (a blocker of protein kinase C) but not by KT-5720. In conclusion, activation of alpha 2-adrenoceptors and somatostatin receptors selectively blocks excitatory responses induced by CADO, most likely by inhibition of adenylyl cyclase and via pertussis toxin-sensitive G proteins. Slow depolarizations induced by substance P are independent of adenylyl cyclase activation and involve activation of protein kinase C.
authors.affiliation: Department of Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Barajas-López
mesh_terms: D015762:2-Chloroadenosine / Q000494:pharmacology; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D000068438:Brimonidine Tartrate; D004594:Electrophysiology; D005260:Female; D006168:Guinea Pigs; D008297:Male; D009474:Neurons / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D047428:Protein Kinase Inhibitors; D011810:Quinoxalines / Q000494:pharmacology; D015398:Signal Transduction; D013004:Somatostatin / Q000494:pharmacology; D013368:Submucous Plexus / Q000166:cytology / Q000502:physiology*; D013373:Substance P / Q000494:pharmacology
chemical_list: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D047428:Protein Kinase Inhibitors; D011810:Quinoxalines; D015762:2-Chloroadenosine; D013373:Substance P; D015240:Phorbol 12,13-Dibutyrate; D000068438:Brimonidine Tartrate; D013004:Somatostatin; D009638:Norepinephrine