EFFECTS OF CLONIDINE AND RILMENIDINE ON CARDIORESPIRATORY AND GASTROINTESTINAL SYSTEMS OF HORSES

Abstract: Clonidine and rilmenidine are drugs used in human medicine as central acting antihypertensive agents due to their actions on the alpha2-adrenoceptor and I1 imidazoline receptors in the central nervous system. Currently, clonidine is also used as a pre-anesthetic medication and in spinal anesthesia, and rilmenidine, despite the lower selectivity for alpha2-adrenergic receptors than clonidine, has also shown antinociceptive potential in experimental pain models. In this study, six horses were submitted to four treatments: R1 group (0.014 mg/kg of rilmenidine); R2 group (0.021 mg/kg of rilmenidine); Clo group (0.002 mg/kg of clonidine), and a control group. The assessment comprehended their heart and respiratory rates, systolic blood pressure and intestinal motility at basal levels and, then, 60 and 120 minutes after the oral administration of the drugs. Rilmenidine decreased heart rate on the two tested doses, which did not occur in the clonidine treatment; slight variations in systolic blood pressure in all treatments and respiratory rate reduction in treatments with rilmenidine at 0.021 mg/kg and clonidine at 0.002 mg/kg were also observed. Further studies with different dosages and varied administration routes are still necessary in order to elucidate more effects of these drugs on horses.

摘要：可乐定（clonidine）与利美尼定（rilmenidine）是人类医学中常用的中枢性抗高血压药物，其作用机制为靶向中枢神经系统内的α2肾上腺素能受体（alpha2-adrenoceptor）与I1咪唑啉受体（I1 imidazoline receptors）。目前，可乐定还被用作麻醉前给药及脊髓麻醉用药；尽管利美尼定对α2肾上腺素能受体的选择性弱于可乐定，但其在实验性疼痛模型中已展现出抗伤害感受潜力。本研究选取6匹试验马，设置4组处理方案：R1组（给药剂量为0.014 mg/kg利美尼定）、R2组（给药剂量为0.021 mg/kg利美尼定）、Clo组（给药剂量为0.002 mg/kg可乐定）以及空白对照组。评估内容涵盖试验马在基础状态下及口服给药后60、120分钟的心率、呼吸频率、收缩压与肠道蠕动功能。结果显示，两种受试剂量的利美尼定均可降低试验马的心率，而可乐定处理组未出现该效应；所有处理组的收缩压均出现小幅波动，且在0.021 mg/kg利美尼定及0.002 mg/kg可乐定处理组中观察到呼吸频率降低的现象。未来仍需开展不同给药剂量与给药途径的相关研究，以进一步阐明这两种药物对马的更多生理效应。