Background and Purpose: The anococcygeus muscle has a classically sympathetic noradrenaline-mediated motor innervation. Owing to its physiological importance, not much work has been done in the study of its muscular response to certain drugs and chemical mediators. The aim of the experiment was to examine the response of rat anococcygeus muscle to selected drugs and field stimulation. Experimental Approach: Anococcygeus smooth muscle was isolated from adult male rat. In this study, we investigated tissue response to acetylcholine (ACh), noradrenaline (NA), guanethidine (Gua), L-NAME, tetrodotoxin (TTX), and to field stimulation. The isolated muscle was suspended in an organ bath containing Krebs solution gassed with O2/CO2 (95%/5%) at 37oC. Responses were measured with Grass FT 03 isometric transducer, displayed on a Grass Polygraph and was statistically analysed using Microsoft® Excel 2008. Key Results: The muscle tissue responded to ACh and NA, with higher response mediated by NA. Nerve tissue was stimulated following field stimulation which was abolished by the presence TTX and Gua. An inhibitory innervation stimulated by nitric oxide (NO), non-adrenergic non-cholinergic (NANC) was abolished by the presence of L-NAME. Conclusion: α1-adrenoceptor and muscarinic receptors are richly distributed in rat anococcygeus muscle, hence their activation by the binding of NA and ACh respectively. There appeared to be preference on NA over ACh in contracting the muscle as its effect was more profound, though its release was prevented by neuro-muscular blockers during the field evoked response. There was complete inhibition of the NO pathway due to the presence of L-NAME.
