ROLE OF NITRIC-OXIDE IN IN-VITRO CONTRACTILE ACTIVITY OF THE 3RD COMPARTMENT OF THE STOMACH IN LLAMAS

Objective-To determine the role of nitric oxide and an apamin-sensitiv e nonadrenergic-noncholinergic inhibitory transmitter in in vitro cont ractile activity of the third compartment in Ilamas. Sample Population -isolated strips of third compartment of the stomach from 5 Ilamas. Pr ocedure-Strips were mounted in tissue baths containing oxygenated Kreb 's buffer solution and connected to a polygraph chart recorder to meas ure contractile activity. Atropine, guanethidine, and indomethacin wer e added to tissue baths to inhibit muscarinic receptors, adrenorecepto rs, and prostaglandin synthesis. Responses to electrical field stimula tion following addition of the nitric oxide antagonist N omega-nitro-L -arginine methyl ester (L-NAME) and apamin were evaluated. Results-Ele ctrical field stimulation (EFS) resulted in a reduction in the amplitu de and frequency of contractile activity, followed by rebound contract ion when EFS was stopped. Addition of L-NAME resulted in a significant reduction in inhibition of contractile activity. Addition of apamin a lso resulted in a significant reduction in inhibitory contractile acti vity at most stimulation frequencies. The combination of L-NAME and ap amin resulted in a significant reduction in inhibition at all frequenc ies. Conclusion-Nitric oxide and a transmitter acting via an apamin-se nsitive mechanism appear to be involved in inhibition of contractile a ctivity of the third compartment in Ilamas. Clinical Relevance-Results suggest that nitric oxide plays an important role in mediating contra ctile activity of the third compartment in Ilamas. Use of nitric oxide synthase inhibitors may have a role in the therapeutic management of Ilamas with lesions of the third compartment.