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      Inhibitory effects of NPY on ganglionic transmission in myenteric neurones of the guinea-pig descending colon.

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          Abstract

          Intracellular recordings were made from myenteric neurones of the guinea-pig descending colon. Neuropeptide Y (NPY) and related pancreatic polypeptides were applied by superfusion and the effects upon the amplitude of fast excitatory synaptic potentials (ESPs) and the ratio of paired fast ESPs evoked by stimulation of internodal fibre tracts were noted. NPY produced a concentration-dependent inhibition in fast ESP amplitude in the majority of neurones (17/21) with a calculated IC50 value of 7 nM; in some neurones this inhibition was mediated via the local release of noradrenaline. Peptide YY (PYY) (eight out of 11 neurones; IC50 = 1 nM), NPY(3-36) (three out of three neurones) and [Leu31, Pro34]NPY (four out of five neurones) also decreased the amplitude of fast ESPs. The effects of two or more pancreatic polypeptides or analogues on fast synaptic transmission were compared directly in six neurones; the apparent relative potency of agonists suggested the involvement of Y2-receptors and at least one other Y-receptor type. In the absence of any direct postsynaptic effects of pancreatic polypeptides on the active or passive properties of myenteric neurones, or on their sensitivity to ionophoretically applied acetylcholine, inhibition of fast ganglionic transmission was presumed to be presynaptic in origin. It is concluded that, in addition to their previously described depressant actions on neuro-effector transmission to colonic smooth muscle, pancreatic polypeptides can exert powerful inhibitory effects on myenteric neurones of the descending colon.

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          Author and article information

          Journal
          Neurogastroenterol. Motil.
          Neurogastroenterology and motility : the official journal of the European Gastrointestinal Motility Society
          1350-1925
          1350-1925
          Feb 2000
          : 12
          : 1
          Affiliations
          [1 ] Department of Biomedical Sciences, University of Aberdeen, Institute of Medical Sciences, Foresterhill, Aberdeen AB9 1AS UK. kbrowni2@hfhs.org
          Article
          nmo178
          10.1046/j.1365-2982.2000.00178.x
          10652114
          54a4fcb5-85cf-435c-ba5d-d1921460cd6a
          History

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