CHARACTERIZATION OF MECHANOSENSITIVE PELVIC NERVE AFFERENT-FIBERS INNERVATING THE COLON OF THE RAT
CHARACTERIZATION OF MECHANOSENSITIVE PELVIC NERVE AFFERENT-FIBERS INNERVATING THE COLON OF THE RAT
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DOI：
10.1152/jn.1994.71.6.2046
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发表时间：
1994-06-01
影响因子：
2.5
通讯作者：
GEBHART, GF
中科院分区：
文献类型：
--
作者：
SENGUPTA, JN;GEBHART, GF
1.在麻醉大鼠中记录S、骶背、根传入纤维的单单位活动。共364传入纤维的骨盆神经的电刺激，并随后测试结直肠扩张（CRD）和膀胱扩张（UBD）的反应。无髓C纤维占67%（n = 244），有髓AG纤维占33%（n = 120）。在最初的三个实验中，通过骨盆神经刺激确定了35根纤维，并测试了仅对CRD的反应;这些纤维中没有一根对CRD有反应。在随后的20个实验中，测试了329个盆神经传入纤维对CRD和UBD的反应。在329根纤维中，34%（n = 112）对伤害性CRD（80 mmHg）或UBD（缓慢充盈≤ 100 mmHg）无反应，44%（n = 146）对UBD有反应，16%（n = 53）对CRD有反应，6%（n = 18）对肛门粘膜的机械刺激有反应.在对CRD有反应的总共53根盆神经传入纤维中，43根（81%）是C纤维（平均：1.5 m/s），10根（19%）是A δ纤维（平均：4.7 m/s）。15条CRD敏感纤维无静息活动，而38条纤维有静息活动（平均值：2.6 imp/s）.重复CRD（80 mmHg，30 s，10次试验，间隔4 min）的反应再现性在17根纤维中进行了测试。在16例中，重复扩张的反应是可重复的，没有证据表明随后的反应是促进或抑制的。在第9次和第10次试验中，一种纤维的反应更大。在44根纤维中研究了对分级CRD的反应。所有纤维表现出单调的，增加刺激反应功能（80毫米汞柱的扩张。在将最小二乘线性回归线外推到纵坐标并在0和40 mmHg之间变化后，确定44根纤维响应的阈值。结肠中的两个骨盆神经传入纤维群是明显的：低阈值（LT）传入纤维的平均阈值为2.9 mmHg（范围：0-10 mmHg; n = 34），高阈值（HT）传入纤维的平均阈值为32.6 mmHg（范围：28.0-40.0 mmHg; n = 10）。缓激肽（BK）的化学敏感性进行了测试，在九个LT纤维。七纤维BK（0.1至100微克/公斤IA）和两个纤维没有响应高达100微克/公斤的BK。BK在三个纤维测试的反应是剂量依赖性的。BK在洛哌丁胺诱导的平滑肌麻痹的存在下产生反应，这表明对BK的反应代表了纤维感受性末梢的直接作用。B-2受体拮抗剂D-Arg-[Hyp（3），Thi（5），D-TiC 7，Oic（8）]-BK阻断了BK对纤维的反应。在肛周粘膜中共发现18条盆神经传入纤维。这些纤维对粘膜感受野的轻微敲击作出突发反应。这18个纤维中有17个对CRD无反应; 1个纤维在阶段性CRD开始时表现出短暂的放电爆发。与结肠传入纤维相比，大多数（77%）粘膜传入纤维是有髓鞘的，平均传导速度为13.6 m/s（n = 14）。4根纤维（23%）为无髓C纤维，平均传导速度为2.0 m/s。
1. Single-unit activity was recorded from S, sacral dorsal,root afferent fibers in the anesthetized rat. A total of 364 afferent fibers were identified by electrical stimulation of the pelvic nerve and subsequently tested for response to colorectal distension (CRD) and urinary bladder distension (UBD). Sixty-seven percent (n = 244) of the fibers were unmyelinated C-fibers and 33% (n = 120) were thinly myelinated AG-fibers.2. In three initial experiments, 35 fibers were identified by pelvic nerve stimulation and tested for response only to CRD; none of these fibers responded to CRD. In 20 subsequent experiments, 329 pelvic nerve afferent fibers were tested for response to CRD and UBD. Thirty-four percent (n = 112) of the 329 fibers were unresponsive to noxious CRD (80 mmHg) or to UBD (slow filling less than or equal to 100 mmHg), 44% (n = 146) responded to UBD, 16% (n = 53) responded to CRD, and 6% (n = 18) responded to mechanical stimulation of the anal mucosa.3. Of the total of 53 pelvic nerve afferent fibers that responded to CRD, 43 (81%) were C-fibers (mean: 1.5 m/s) and 10 (19%) were A delta-fibers (mean: 4.7 m/s). Fifteen of the CRD-sensitive fibers had no resting activity, whereas 38 fibers exhibited some resting activity (mean: 2.6 imp/s).4. Reproducibility of responses to repeated CRD (80 mmHg, 30s, 10 trials at 4-min intervals) was tested in 17 fibers. In 16, responses to repeated distension were reproducible without evidence of facilitation or inhibition of subsequent responses. One fiber gave greater responses during the 9th and 10th trials.5. Responses to graded CRD were studied in 44 fibers. All fibers exhibited monotonic, increasing stimulus-response functions (80 mmHg of distension. Thresholds for response of the 44 fibers were determined after extrapolation of the least-squares linear-regression line to the ordinate and varied between 0 and 40 mmHg. Two populations of pelvic nerve afferent fibers in the colon were apparent: low threshold (LT) afferent fibers had a mean threshold of 2.9 mmHg (range: 0-10 mmHg; n = 34) and high threshold (HT) afferent fibers had a mean threshold of 32.6 mmHg (range: 28.0-40.0 mmHg; n = 10).6. Chemosensitivity to bradykinin (BK) was tested in nine LT fibers. Seven fibers responded to BK (0.1 to 100 mu g/kg ia) and two fibers did not respond up to 100 mu g/kg of BK. Responses to BK tested in three fibers were dose dependent. BK produced responses in the presence of loperamide-induced smooth muscle paralysis, suggesting that responses to BK represent a direct action at the fibers' receptive endings. D-Arg-[Hyp(3),Thi(5),D-TiC7,Oic(8)]-BK, a B-2- receptor antagonist, blocked responses of the fibers to BK.7. A total of 18 pelvic nerve afferent fibers were identified in the perianal mucosa. These fibers responded with a burst to light stroking of mucosal receptive fields. Seventeen of these 18 fibers were unresponsive to CRD; 1 fiber exhibited a transient burst of discharge at the onset of phasic CRD. The majority (77%) of the mucosal afferent fibers, in contrast to colonic afferent fibers, were myelinated with a mean conduction velocity of 13.6 m/s (n = 14). Four fibers (23%) were unmyelinated C-fibers with a mean conduction velocity of 2.0 m/s.