MacNaughton Wallace K, Van Sickle Marja D, Keenan Catherine M, Cushing Kelly, Mackie Ken, Sharkey Keith A
Dept. of Physiology and Biophysics, Univ. of Calgary, 3330 Hospital Dr. NW, Calgary, AB, T2N 4N1, Canada.
Am J Physiol Gastrointest Liver Physiol. 2004 May;286(5):G863-71. doi: 10.1152/ajpgi.00482.2003. Epub 2003 Dec 30.
We investigated the distribution and function of cannabinoid (CB)(1) receptors in the submucosal plexus of the guinea pig ileum. CB(1) receptors were found on both types of submucosal secretomotor neurons, colocalizing with VIP and neuropeptide Y (NPY), the noncholinergic and cholinergic secretomotor neurons, respectively. CB(1) receptors colocalized with transient receptor potential vanilloid-1 receptors on paravascular nerves and fibers in the submucosal plexus. In the submucosal ganglia, these nerves were preferentially localized at the periphery of the ganglia. In denervated ileal segments, CB(1) receptor immunoreactivity in submucosal neurons was not modified, but paravascular and intraganglionic fiber staining was absent. Short-circuit current (I(sc)) was measured as an indicator of net electrogenic ion transport in Ussing chambers. In the ion-transport studies, I(sc) responses to capsaicin, which activates extrinsic primary afferents, and to electrical field stimulation (EFS) were reduced by pretreatment with the muscarinic antagonist atropine, abolished by tetrodotoxin, but were unaffected by VIP receptor desensitization, hexamethonium, alpha-amino-3-hydroxy-5-methlisoxazole-4-proprionic acid, or N-methyl-d-aspartate glutamate receptor antagonists. The responses to capsaicin and EFS were reduced by 47 +/- 12 and 30 +/- 14%, respectively, by the CB(1) receptor agonist WIN 55,212-2. This inhibitory effect was blocked by the CB(1) receptor antagonist, SR 141716A. I(sc) responses to forskolin or carbachol, which act directly on the epithelium, were not affected by WIN 55,212-2. The inhibitory effect of WIN 55,212-2 on EFS-evoked secretion was not observed in extrinsically denervated segments of ileum. Taken together, these data show cannabinoids act at CB(1) receptors on extrinsic primary afferent nerves, inhibiting the release of transmitters that act on cholinergic secretomotor pathways.
我们研究了豚鼠回肠黏膜下神经丛中大麻素（CB）(1)受体的分布和功能。在两种类型的黏膜下分泌运动神经元上均发现了CB(1)受体，分别与血管活性肠肽（VIP）和神经肽Y（NPY）共定位，它们分别是非胆碱能和胆碱能分泌运动神经元。CB(1)受体与黏膜下神经丛中血管周围神经和纤维上的瞬时受体电位香草酸受体1共定位。在黏膜下神经节中，这些神经优先定位于神经节的周边。在去神经的回肠段，黏膜下神经元中的CB(1)受体免疫反应性未改变，但血管周围和神经节内纤维染色缺失。短路电流（I(sc)）作为Ussing小室中净电致离子转运的指标进行测量。在离子转运研究中，毒蕈碱拮抗剂阿托品预处理可降低对辣椒素（激活外在初级传入神经）和电场刺激（EFS）的I(sc)反应，河豚毒素可消除该反应，但VIP受体脱敏、六甲铵、α-氨基-3-羟基-5-甲基异恶唑-4-丙酸或N-甲基-D-天冬氨酸谷氨酸受体拮抗剂对其无影响。CB(1)受体激动剂WIN 55,212-2分别使对辣椒素和EFS的反应降低了47±12%和30±14%。这种抑制作用被CB(1)受体拮抗剂SR 141716A阻断。对直接作用于上皮的福斯可林或卡巴胆碱的I(sc)反应不受WIN 55,212-2影响。在回肠的外在去神经段未观察到WIN 55,212-2对EFS诱发分泌的抑制作用。综上所述，这些数据表明大麻素作用于外在初级传入神经上的CB(1)受体，抑制作用于胆碱能分泌运动途径的递质释放。
