A possible role of the L‐arginine‐nitric oxide pathway in the modulation of cholinergic transmission in the guinea‐pig taenia coli

Abstract

1 The role of the L-arginine-nitric oxide (NO) pathway for non-adrenergic, non-cholinergic (NANC) relaxation of the guinea-pig taenia coli was studied by recording isometric tension in response to transmural field stimulation (TMS). inhibited these effects of L-NNA. L-NNA (l0-4 M) had no effect on the inhibitory response during TMS in strips preincubated with atropine (10-6M). 6 In conclusion, the L-arginine-NO pathway seems to play a role in the NANC innervation of the guinea-pig taenia coli. The inhibitory effect of NO or a NO-like compound depends on the integrity of the cholinergic pathways and it is proposed that this compound exerts its effects prejunctionally on cholinergic nerves, by inhibiting the release of acetylcholine.

Rhythmic changes in colonic motility are regulated by period genes

“…This increased contractile response in the presence of L-NAME is consistent with observations by others (1,15,25) and indicates that inhibition of nNOS, through blockage of the synthesis of the inhibitory neurotransmitter nitric oxide, increases cholinergic contractions. However, the precise mechanism through which inhibition of nNOS increases the contractile response remains to be defined.…”

“…Muscle contractions occur only when the inhibitory neurons are "switched off" (27). This is based on the following observations: 1) blockade of sodium channels by the neurotoxin TTX (which inhibits the release of neurotransmitters) stimulates muscle contractions (13,26) and 2) blockade of nNOS by L-NAME enhances acetylcholineevoked smooth muscle contraction (1,15,25). We therefore first explored the role of neural mediation by determining the effect of acetylcholine on colonic circular muscle contractility of WT mice in the presence of the neurotoxin TTX.…”

Differential effects of nitric oxide donors on basal and electrically evoked release of acetylcholine from guinea‐pig myenteric neurones

“…The release experiments are corroborated by contraction studies: sodium nitroprusside depressed the cholinergic contraction elicited by electrical stimulation of gastric smooth muscle, but did not influence the contraction caused by exogenous acetylcholine (Baccari et al, 1994). Vice versa, inhibitors of NO synthase enhanced the electrically induced cholinergic contractions of guinea-pig ileum and taenia coli (Knudsen & Tottrup, 1992;Wiklund et al, 1993b), and of rat and rabbit stomach (Lefebvre et al, 1992;Baccari et al, 1993). All this suggests that NO is able to inhibit the cholinergic motor neurotransmission in the gastrointestinal tract.…”

Inhibitory action of PPADS on relaxant responses to adenine nucleotides or electrical field stimulation in guinea‐pig taenia coli and rat duodenum

“…Acetylcholine is released as an excitatory transmitter by EFS causing contraction of the taenia coli (Knudsen & T0ttrup, 1992). This effect could not be abolished by atropine in the present study because the experiments were carried out on the carbachol-contracted taenia coli.…”

“…Also, nitric oxide (NO) has been discussed as NANC-transmitter in the gut. However, in the guinea-pig taenia coli the predominant part of the inhibitory NANC response is not mediated by NO (Knudsen & T0ttrup, 1992).…”