STIMULUS-RESPONSE FUNCTION STUDIES OF ESOPHAGEAL MECHANOSENSITIVE NOCICEPTORS IN SYMPATHETIC AFFERENTS OF OPOSSUM

被引:131
作者
SENGUPTA, JN
SAHA, JK
GOYAL, RK
机构
[1] HARVARD UNIV,BETH ISRAEL HOSP,SCH MED,DEPT MED,DIV GASTROENTEROL,THORNDIKE LAB,330 BROOKLINE AVE,BOSTON,MA 02215
[2] HARVARD UNIV,SCH MED,CHARLES A DANA RES INST,CTR DIGEST DIS,BOSTON,MA 02115
关键词
D O I
10.1152/jn.1990.64.3.796
中图分类号
Q189 [神经科学];
学科分类号
071006 ;
摘要
Single-unit activity was recorded from afferent fibers in either the paravertebral sympathetic chain or the splanchnic nerves. Forty-three fibers that responded to distension of the smooth-muscle portion of esophagus were selected for further study. Out of the 43 fibers, 27 (62%) had ongoing resting activity, and 16 (38%) were silent. The mean resting activity of these fibers was 0.28 ± 0.06 imp/s (range, 0-2.6 imp/s). Repeated distensions of the esophagus to a fixed pressure (80 mmHg) evoked spike discharge at a reproducible rate. There was no evidence of facilitation or inhibition of subsequent responses. The mean coefficient of variation (CV) was 0.17 ± 0.05 imp/s (n = 5). The stimulus-response function (SRF) to intraluminal graded distension was studied in 35 fibers. Thirty-three fibers showed linear increase in firing that did not saturate up to 120 mmHg. Two fibers reached maximal discharge rate at 60 mmHg. The mean discharge rate at 120 mmHg pressure was 14.87 ± 1.52 imp/s. Threshold pressure for activation of each fiber was calculated by a least-squares linear-regression plot of the SRF. The threshold pressure varied from 0 to 50 mmHg (mean, 16.21 ± 2.86 mmHg). The distribution profile of the threshold values showed that there were two separate populations of mechanosensitive receptors: 1) wide-dynamic-range mechanonociceptors (WDR-MN) with mean threshold pressure of 2.89 ± 0.75 mmHg (range, 0-7 mmHg; n = 22); and 2) high-threshold mechanonociceptors (HT-MN) with mean threshold of 33.26 ± 2.52 mmHg (range, 19-50 mmHg; n = 13). Discharge evoked by esophageal peristalsis was studied in five WDR-MN and five HT-MN units. Whereas all five WDR-MN units (threshold value, 2.6 ± 0.96 mmHg) responded to peristalsis, none of the HT-MN units (threshold value, 31.2 ± 4.01 mmHg) did so. The mean response to peristaltic contraction in WDR-MN units was 5.32 ± 1.36 imp/s, which was 24.7% of the maximal response (21.53 ± 1.92 imp/s; n = 5) at 120 mmHg. The duration of evoked response to peristaltic contraction was 10-12 s. The activity profile of the units to 60-s balloon distension at near threshold and higher pressures showed three patterns: 1) rapid adaptation, 2) slow adaptation, and 3) slow adaptation with after discharge. The rapidly adapting fibers became slowly adapting with greater degrees of esophageal distension. The units that showed rapid or slow adaptation at low-distension pressure became indistinguishable from one another at high-distension pressure. All fibers showed an initial burst of phasic discharge followed by a tonic discharge that lasted through the period of distension. The after discharging units (n = 6) showed evoked activity that outlasted the distension period. Such poststimulus activity was observed at every pressure level. The mean duration of discharge beyond the stimulus was 276.6 ± 32.4 s with distension pressure of 120 mmHg. The conduction velocities were measured in 38 fibers. They varied from 0.32 to 7.8 m/s (mean, 2.66 ± 0.28 m/s). Twenty-three (63%) fibers had conduction velocity <2.5 m/s (C-fibers); and 15 (40%) fibers were between 2.5 to 7.8 m/s (A-δ fibers). There was no correlation between conduction velocity, resting activity, and maximum response of the fibers. The WDR-MN and HT-MN could not be distinguished on the basis of their conduction velocity, resting activity, maximum discharge rate, or adaptation profile. The rapidly adapting, slowly adapting, and after discharging fibers could not be differentiated on the basis of conduction velocity, resting discharge, maximum discharge rate, or threshold pressure. It is concluded that 1) sympathetic esophageal mechanosensitive receptors are mostly nociceptors, 2) these nociceptors are of two types - WDR-MN and HT-MN, 3) the WDR-MN may subserve both physiological reflex function as well as nociception, 4) the HT-MN may encode noxious stimuli and serve primarily as specific nociceptors, 5) these mechanonociceptors (MN) appear to be present 'in series' with the esophageal longitudinal muscle, and 6) the behavior of sympathetic-esophageal-mechanosensitive receptors is quite different from the previously described vagal low-threshold mechanoreceptors (LTM), which serve as 'pure' mechanoreceptors.
引用
收藏
页码:796 / 812
页数:17
相关论文
共 80 条
  • [1] VAGAL AFFERENT INHIBITION OF PRIMATE THORACIC SPINOTHALAMIC NEURONS
    AMMONS, WS
    BLAIR, RW
    FOREMAN, RD
    [J]. JOURNAL OF NEUROPHYSIOLOGY, 1983, 50 (04) : 926 - 940
  • [2] CARDIOVASCULAR AND T2-T4 DORSAL HORN CELL RESPONSES TO GALLBLADDER DISTENSION IN THE CAT
    AMMONS, WS
    FOREMAN, RD
    [J]. BRAIN RESEARCH, 1984, 321 (02) : 267 - 277
  • [3] THE NERVOUS CONTROL OF THE CERVICAL OESOPHAGUS OF THE RAT DURING SWALLOWING
    ANDREW, BL
    [J]. JOURNAL OF PHYSIOLOGY-LONDON, 1956, 134 (03): : 729 - 740
  • [4] ANDREWS PLR, 1986, PROG BRAIN RES, V67, P65
  • [5] RESPONSES OF SACRAL VISCERAL AFFERENTS FROM THE LOWER URINARY-TRACT, COLON AND ANUS TO MECHANICAL STIMULATION
    BAHNS, E
    HALSBAND, U
    JANIG, W
    [J]. PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY, 1987, 410 (03): : 296 - 303
  • [6] DISCHARGE PROPERTIES OF MECHANOSENSITIVE AFFERENTS SUPPLYING THE RETROPERITONEAL SPACE
    BAHNS, E
    ERNSBERGER, U
    JANIG, W
    NELKE, A
    [J]. PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY, 1986, 407 (05): : 519 - 525
  • [7] SEARCH FOR A CARDIAC NOCICEPTOR - STIMULATION BY BRADYKININ OF SYMPATHETIC AFFERENT NERVE-ENDINGS IN THE HEART OF THE CAT
    BAKER, DG
    COLERIDGE, HM
    COLERIDGE, JCG
    NERDRUM, T
    [J]. JOURNAL OF PHYSIOLOGY-LONDON, 1980, 306 (SEP): : 519 - 536
  • [8] AFFERENT-FIBERS SUPPLYING THE UTERUS IN THE RAT
    BERKLEY, KJ
    ROBBINS, A
    SATO, Y
    [J]. JOURNAL OF NEUROPHYSIOLOGY, 1988, 59 (01) : 142 - 163
  • [9] FUNCTIONAL-PROPERTIES OF AFFERENT-FIBERS SUPPLYING REPRODUCTIVE AND OTHER PELVIC ORGANS IN PELVIC NERVE OF FEMALE RAT
    BERKLEY, KJ
    HOTTA, H
    ROBBINS, A
    SATO, Y
    [J]. JOURNAL OF NEUROPHYSIOLOGY, 1990, 63 (02) : 256 - 272
  • [10] RESPONSE OF CUTANEOUS SENSORY UNITS WITH UNMYELINATED FIBERS TO NOXIOUS STIMULI
    BESSOU, P
    PERL, ER
    SCHMITTR.LA
    [J]. JOURNAL OF NEUROPHYSIOLOGY, 1969, 32 (06) : 1025 - &