Abstracts
1999 Digestive Disease Week

# 2168 NEURAL INHIBITION IN JEJUNAL CIRCULAR MUSCLE AFTER SMALL BOWEL TRANSPLANTATION(SBT): NITRIC OXIDE (NO) HAS NO APPARENT ROLE
B M Balsiger, J A Duenes, N Ohtani, C Shibata, W J Anding, Michael G Sarr, Mayo Clin, Rochester, MN

Nonadrenergic/noncholinergic (NANC) inhibitory neural controal of gut smooth muscle is important in regulation of motor activity and is believed to be largely mediated by NO. AIMS: To study the role of NO in regulation of intestinal smooth muscle contractility before and after SBT. METHODS: Strips of jejunal circular muscle were harvested from rats after syngeneic (no rejection) small bowel transplantation (SBT) at 1 week (SBT1) and 8 weeks (SBT8) postoperatively and after sham celiotomy (SC). We evaluated in vitro contractile response to NO (3·10-6-3·10-5M) and electrical field stimulation (EFS, 20V, 4 msec pulse width, 10 sec duration) at 1 - 10 Hz (which excites all intrinsic nerves within muscle strip) under adrenergic/cholinergic blockade (to avoid confounding effects of cholinergic and adrenergic neurotransmitters) with and without 10-3M L-NMMA (NO synthase inhibitor), and 10-5M methylene blue (MB, soluble guanylate synthase inhibitor). Contractile activity was quantitated as area under the contractile curve. RESULTS: Spontaneous activity (g·5 min/mg) did not differ between groups (SBT1 4.3±0.5, SBT8 4.0±0.4, and SC 5.0±0.5). Exogenous NO had no inhibitory effect on basal tone or phasic activity in any group. EFS inhibited contractile activity similarly in SC, SBT1 and SBT8 (Table), L-NMMA and MB did not affect EFS-induced inhibition in any group. SUMMARY: SBT did alter spontaneous activity nor response to EFS. L-NMMA and MB surprisingly did not affect EFS-induced inhibitory response. Exogenous NO had no effect on contractile activity. CONCLUSIONS: NO does not appear to play a role in NANC inhibition of rat jejunal circular smooth muscle. SBT does not alter NANC inhibitory function. These results differ from the results in jejunal longitudinal muscle (GE 114:A1377, 1998), suggesting neural control markedly differs between muscle layers of the jejunum. Support: NIH DK39337 (MGS).

(Hz)	1	3	5	7	10
SC	-79±12†	-110±10†	-96±9†	-71±12†	8±17
SBT1	-50±18	-89±17	-72±17†	-30±11	48±18
SBT8	-90±13†	118±13†	-105±13†	-71±14†	1±20
Values: D% basal activity, mean±SEM; n³8 rats, †p<0.007 to 100%.

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