HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by North, R A Articles by Surprenant, A Search for Related Content PubMed PubMed Citation Articles by North, R A Articles by Surprenant, A

Intracellular recordings were made from guinea-pig myenteric and submucous plexus neurones. Nicotinic excitatory post-synaptic potentials (fast e.p.s.p.s) and slow e.p.s.p.s were recorded in both plexuses; adrenergic inhibitory post-synaptic potentials (i.p.s.p.s) were recorded from submucous plexus neurones. The effects of muscarinic agonists and antagonists were examined on the synaptic potentials in those neurones in which these substances did not change the membrane potential. Muscarine, oxotremorine, methylfurmethide and McNeil A343 reversibly depressed the amplitude of the fast e.p.s.p. in a concentration-dependent way. Hyoscine, pirenzepine and 4-diphenylacetoxy-N-methyl-piperidine (4-DAMP) caused a parallel shift to the right of the agonist dose-response curves. These muscarinic antagonists themselves did not alter the amplitudes of fast e.p.s.p.s evoked by low frequency (0.05-0.1 Hz) stimulation. Antagonist pA2 values (the negative logarithm of the dissociation equilibrium constant) were determined while recording from individual neurones. pA2 values were: pirenzepine 7.0, hyoscine 8.9, and 4-DAMP 8.7. I.p.s.p.s in the submucous plexus were also depressed by muscarinic agonists, and this was competitively reversed by pirenzepine and 4-DAMP, with apparent pA2 values of 6.9 and 8.7 respectively. Muscarinic antagonists alone increased the amplitude of the i.p.s.p. evoked either by single or repeated stimuli. This enhancement was observed with low concentrations of antagonists and did not become greater when the concentrations were increased. Muscarinic agonists depolarized about one-quarter of myenteric and submucous plexus neurones. Low concentrations of pirenzepine antagonized these depolarizations; the pA2 value was 8.4. Cholinergic slow e.p.s.p.s recorded in some myenteric neurones were depressed or abolished by pirenzepine; concentrations that caused 50% inhibition (IC50) for this action ranged from 10 to 60 nM. It is concluded that presynaptic muscarinic receptors, activation of which inhibits the release of acetylcholine and noradrenaline, are the m2 type. Post-synaptic muscarinic receptors, activation of which depolarizes the membrane, are of the m1 type. The results also suggest that acetylcholine may exert a tonic inhibition of noradrenaline release in the submucous plexus through m2 receptors, and mediates the slow e.p.s.p. in the myenteric plexus through m1 receptors.

This article has been cited by other articles:

				C. L. Frisby, R. J. Fraser, M. B. Schirmer, E. K. Yeoh, and L. A. Blackshaw Roles of muscarinic receptor subtypes in small intestinal motor dysfunction in acute radiation enteritis Am J Physiol Gastrointest Liver Physiol, July 1, 2007; 293(1): G121 - G127. [Abstract] [Full Text] [PDF]

				E. A. Thomas, H. Sjovall, and J. C. Bornstein Computational model of the migrating motor complex of the small intestine Am J Physiol Gastrointest Liver Physiol, April 1, 2004; 286(4): G564 - G572. [Abstract] [Full Text] [PDF]

				E. N. Brown and J. J. Galligan Muscarinic receptors couple to modulation of nicotinic ACh receptor desensitization in myenteric neurons Am J Physiol Gastrointest Liver Physiol, June 9, 2003; 285(1): G37 - G44. [Abstract] [Full Text] [PDF]

				D. A. Schneider, M. Perrone, and J. J. Galligan Nicotinic Acetylcholine Receptors at Sites of Neurotransmitter Release to the Guinea Pig Intestinal Circular Muscle J. Pharmacol. Exp. Ther., July 1, 2000; 294(1): 363 - 369. [Abstract] [Full Text]

				P. Vanden Berghe, J. Tack, A. Andrioli, L. Missiaen, and J. Janssens Receptor-induced Ca2+ signaling in cultured myenteric neurons Am J Physiol Gastrointest Liver Physiol, June 1, 2000; 278(6): G905 - G914. [Abstract] [Full Text] [PDF]

				E. S. Vizi Role of High-Affinity Receptors and Membrane Transporters in Nonsynaptic Communication and Drug Action in the Central Nervous System Pharmacol. Rev., March 1, 2000; 52(1): 63 - 90. [Abstract] [Full Text] [PDF]

				W. H. Percy, J. M. Warren, and J. T. Brunz Characteristics of the muscularis mucosae in the acid-secreting region of the rabbit stomach Am J Physiol Gastrointest Liver Physiol, May 1, 1999; 276(5): G1213 - G1220. [Abstract] [Full Text] [PDF]

				F. Berlioz, S. Julien, A. Tsocas, J. Chariot, C. Carbon, R. Farinotti, and C. Rozé Neural Modulation of Cephalexin Intestinal Absorption Through the Di- and Tripeptide Brush Border Transporter of Rat Jejunum In Vivo J. Pharmacol. Exp. Ther., March 1, 1999; 288(3): 1037 - 1044. [Abstract] [Full Text]

				O. Sacchi, M. L. Rossi, R. Canella, and R. Fesce Synaptic Current at the Rat Ganglionic Synapse and Its Interactions With the Neuronal Voltage-Dependent Currents J Neurophysiol, February 1, 1998; 79(2): 727 - 742. [Abstract] [Full Text] [PDF]

				H. E. Shannon, M. J. Sheardown, F. P. Bymaster, D. O. Calligaro, N. W. Delapp, J. Gidda, C. H. Mitch, B. D. Sawyer, P. W. Stengel, J. S. Ward, et al. Pharmacology of Butylthio[2.2.2] (LY297802/NNC11-1053): A Novel Analgesic with Mixed Muscarinic Receptor Agonist and Antagonist Activity J. Pharmacol. Exp. Ther., May 1, 1997; 281(2): 884 - 894. [Abstract] [Full Text]

				S. Matsumoto Functional Evidence of Excitatory M1 Receptors in the Rabbit Airway J. Pharmacol. Exp. Ther., April 1, 1997; 281(1): 531 - 539. [Abstract] [Full Text]