Key result
The L-arginine-nitric oxide pathway inhibitor L-NNA concentration-dependently reduced the latency and amplitude of 'off'-contractions in opossum esophageal muscle strips.
The L-arginine-nitric oxide pathway plays a crucial role in mediating the latency and amplitude of 'off'-contractions in the nonadrenergic, noncholinergic nerves of the opossum esophagus.
Supports NO in opossum esophageal NANC nerves; leaves open human motility relevance or therapeutic translation.
Circular muscle strips from the opossum esophageal body obtained 3-5 cm above the esophagogastric junction were suspended in organ baths for measurement of isometric tension. Stimulation of nonadrenergic, noncholinergic (NANC) inhibitory nerves was performed using transmural field stimulation (TMS). During TMS, no mechanical response was elicited. After cessation of the stimulus a short period, also without mechanical response, intervened, and this period is called latency. The latency was followed by the 'off'-contraction. In control preparations, the latency and the amplitude of the 'off'-contraction were 1.47 +/- 0.17 s, and 3.8 +/- 0.9 mN, respectively. The inhibitor of the L-arginine-nitric oxide (NO) pathway, NG-nitro-L-arginine (L-NNA) concentration-dependently reduced the latency at concentrations greater than 10(-6) M (n = 6-7). At the highest concentration of L-NNA (10(-4) M), 'off' contractions were no longer seen. In 5 out of 7 preparations exposed to L-NNA (10(-4) M), a small contraction was seen during stimulation, and this contraction was abolished by atropine (10(-6) M) in all strips. L-NNA concentration-dependently reduced the amplitude of contractions at concentrations greater than 10(-6) M (n = 6-7). At 10(-4) M, the amplitude was reduced to 3 +/- 2% of that of the initial contraction. Preincubation with L-arginine (10(-5) M) had no influence on the latency. The effects of L-NNA on both latency and the amplitude of contraction were antagonized by preincubation with L-arginine (10(-5) M). Atropine (10(-6) M had no effect on the amplitude of the 'off'-contraction in control preparations.(ABSTRACT TRUNCATED AT 250 WORDS)
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Knudsen et al. (2008) studied this question. NG-nitro-L-arginine (L-NNA) vs. Control preparations was evaluated on Latency and amplitude of the 'off'-contraction. The L-arginine-nitric oxide pathway inhibitor L-NNA concentration-dependently reduced the latency and amplitude of 'off'-contractions in opossum esophageal muscle strips.
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