Influence of adrenergic and cholinergic mediators on the equine jejunum in vitro

Thumbnail Image

Persistent link to this item

View Statistics

Journal Title

Journal ISSN

Volume Title


Influence of adrenergic and cholinergic mediators on the equine jejunum in vitro

Published Date



American Veterinary Medical Association




OBJECTIVE: To characterize the response of equine jejunal smooth muscle to adrenergic and cholinergic mediators. DESIGN: Evaluation of myogenic responses, using an in vitro model. SAMPLE POPULATION: Intestinal tissues were obtained from horses without gastrointestinal tract disorders or systemic disease. PROCEDURE: Baseline myogenic tone and amplitude and frequency of contraction were determined for suspended jejunal muscle strips. The level of adrenergic and cholinergic regulation was assessed, using atropine and adrenoceptor antagonists. The response of the muscles to norepinephrine was characterized, using adrenergic blockade and alpha- and beta-agonists. RESULTS: Adrenergic and cholinergic blockade had minimal effect on baseline myogenic activity. However, alpha 1- and beta 2-agonists induced significant (P < 0.05) decreases in the amplitude and frequency of contraction. Surprisingly, alpha 2-agonists caused an increase in the contraction amplitude of longitudinal muscle fibers (neurogenic in origin). Change in circular muscle activity was not induced by alpha 2-agonists. Norepinephrine induced a similar selective response and was inhibited by yohimbine. CONCLUSIONS: Baseline jejunal activity appears to be myogenic in origin and can function independently of sympathetic and parasympathetic input. However, intestinal smooth muscle can be affected by adrenergic agonists and potentially by increased concentrations of circulating catecholamines. Norepinephrine may act by altering the activity of other neurotransmitters. Differing responses between circular and longitudinal muscle fibers indicates a need to evaluate both components. CLINICAL RELEVANCE: Selective alpha 2-agonists may be potentially useful for motility modification of the equine jejunum. Therapeutic use of adrenergic blockade will be effective only in cases of increased adrenergic stimulation


Related to




Series/Report Number

Funding information

Isbn identifier

Doi identifier

Previously Published Citation

Am J Vet Res. 1996 Jun;57(6):884-90.

Suggested citation

Malone, ED; Brown, DR; Trent, AM; Turner, TA. (1996). Influence of adrenergic and cholinergic mediators on the equine jejunum in vitro. Retrieved from the University Digital Conservancy,

Content distributed via the University Digital Conservancy may be subject to additional license and use restrictions applied by the depositor. By using these files, users agree to the Terms of Use. Materials in the UDC may contain content that is disturbing and/or harmful. For more information, please see our statement on harmful content in digital repositories.