Central distribution of nociceptive intradental afferent nerve fibers in the rat

The central distribution of intradental afferent nerve fibers was investigated by combining electron microscopic observations with a selective method for inducing degeneration of the A delta- and C-type afferent fibers. Degenerating terminals were found on the proprioceptive mesencephalic trigeminal neurons and on dendrites in the neuropil of the trigeminal motor nucleus after application of capsaicin to the rat's lower incisor tooth pulp. The results give anatomical evidence of new sites of central projection of intradental A delta- and C-type fibers whereby the nociceptive information from the tooth pulp can affect jaw muscle activity.     

Termination areas of primary afferent fibers of the trigeminal nerve in the rat

The cobalt-labelling technique was used to investigate the termination areas of trigeminal primary afferent fibers. The familiar somatotopic arrangement of fibers and terminals of the three divisions of the trigeminal nerve was recognized both in the spinal tract and in the nuclear complex of the trigeminus. The spinal tract could be traced as far as the 3rd cervical segment of the spinal cord where fibers crossed to the contralateral side. The different divisions of the nuclear complex could be unambiguously defined on the basis of the pattern of fiber terminations. The nucleus principalis was characterized by the even distribution of terminals in the nucleus. The nucleus spinalis was characterized by small bundles of fibers of intranuclear origin, which broke up the even distribution pattern of terminals. The presence of mesencephalic trigeminal fibers in the nucleus oralis distinguished this nucleus from the nucleus interpolaris. The nucleus caudalis was recognized on the ground of its striated structure. Primary trigeminal afferent fibers were located in the following sites: in the solitary nucleus, in the lateral part of the reticular formation, in the dorsal-column nuclei and in the superior vestibular nuclei. Primary fiber terminations could not be observed in the cerebellum.     

Spatial properties of receptive fields of mechanosensitive primary afferent nerve fibers

Tactile sensation is rich and varied, requiring input from a variety of mechanoreceptors whose spatiotemporal aspects deserve careful study. Recent data for virtually every class of sensitive mechanoreceptor have revealed spatial inhomogeneities in sensitivity reflecting the distribution of sense organ terminals and the complexity of gradients in the complex spatial organization of receptive fields. Controlled surface parallel stimulation provides a means for examining sensitivity in a manner that may shed light on active tactile exploration and allow quantitative analysis of orientation, direction, and velocity properties underlying some aspects of feature extraction by the central nervous system.     

Morphological changes in the electrically inactive afferent myelinated nerve fibers of the live clustered neuroreceptor

At attempt has been made to determine morphological criterium of active and inactive alive afferent myelin fibers. Applying electrophysiological control, external diameters in the area of maximal dilatation of the myelin fiber are compared with the neighbouring maximal narrowing of the unmyelinated preterminal. The dilatation coefficient, suggested by the authors of mathematical models of the nervous fiber is taken as the base of estimation. When the dilatation coefficient is more than five, the fiber is considered to be inactive. The active and inactive nervous fibers are stated to possess certain morphological differences. They are observed not only in the first myelin segment area, but in the second one, and sometimes--in the third and fourth segments. Morphological characteristics of these segments make it possible to suggest that electrical impulse can be blocked. From our data it is possible to think that not only the first myelin segment and the first node of Ranvier, but also the successive segment and nodes of Ranvier influence the impulse passing.     

肾动脉内注射辣椒素兴奋肾神经传入纤维的自发活动

应用记录肾传入神经多单位和单位放电的方法,观察肾动脉内注射辣椒素对麻醉家兔肾神经传入纤维自发放电活动的影响。结果表明：(1)肾动脉内注射辣椒素20、40和60nmol／kg可呈剂量依赖性地兴奋肾传入纤维的活动,而动脉血压不变;(2)静脉内预先应用辣椒素受体阻断剂钌红(40mmol／kg),可完全阻断辣椒素对肾传人纤维的兴奋作用。(3)静脉内预先注射一氧化氮合酶抑制剂L-NAME(0．1mmol／kg),能延长并增强肾传入神经对辣椒素的反应。以上结果提示：肾动脉内应用辣椒素可兴奋肾传人纤维的自发放电活动。一氧化氮作为抑制因素参与辣椒素诱导的肾传入神经兴奋。     

肾动脉内注射L-精氨酸抑制肾神经传入纤维的自发活动

研究旨在应用记录肾传人神经多单位和单位放电的方法,观察肾动脉内注射L—精氨酸对麻醉家兔肾神经传人纤维自发放电活动的影响。结果表明：(1）肾动脉内注射L—精氨酸(0．05、0．24和0．48mmol/kg)可呈剂量依赖性地抑制肾传人纤维的活动,而动脉血压不变;(2)静脉内预先注射一氧化氮合酶抑制剂L—NAME(0．11mmol/kg),可完全阻断L—精氨酸对肾传人纤维的抑制;(3)肾动脉注射一氧化氮(N0)供体SIN—1(3．75μmol/kg)也可抑制肾传入神经的活动。以上结果提示：肾动脉内应用N0前体L—精氨酸和N0供体SIN—1均可抑制肾传入纤维的自发活动。     

肾动脉内注射腺苷兴奋肾神经传入纤维的自发活动

应用记录肾神经传入纤维多单位和单位放电的方法,观察肾动脉内注射腺苷对麻醉家兔肾神经传入纤维自发放电活动的影响。结果表明：(1)肾动脉内注射50,100和200nmol／kg腺苷可呈剂量依赖性地兴奋肾神经传入纤维的活动,而动脉血压不变。(2)肾动脉内预先应用选择性腺苷A1受体阻断剂DPCPX(160nmol/kg),可部分阻断腺苷对肾神经传入纤维的兴奋作用。(3)静脉应用一氧化氮合酶抑制剂L-NAME(0．1mmol／kg)预处理,延长并增强了肾神经传入纤维对腺苷的反应。以上结果提示,肾动脉内应用腺苷可兴奋肾传入纤维的自发放电活动,一氧化氮作为抑制性因素参与腺苷诱导的肾神经传入纤维兴奋。     

Reaction of the hypothalamo-hypophyseal system of cats to stimulation of the cervical sympathetic nerve and the afferent fibers of the vagus nerve]

Data are presented on the functional morphology of the hypothalamo-hypophysial neurosecretory system of cats in stimulation of the cervical sympathetic nerve and of the afferent fibers of the vagus. Stimulation of the sympathetic nerve selectively activated the supraoptic nucleus and caused the discharge of the neurohormones from the posterior lobe of the hypophysis, whereas its infundibular portion contained much neurosecretory material. In response to the stimulation of the vagus all the portions of the neurohypophysis were released of the Gomori-positive substance; both the supraoptic and the paraventricular nucleus were activated.     

Parameters of conduction via afferent nerve fibers in mice with streptozotocin-induced and genetically determined diabetes

The parameters of conduction via afferent nerve fibers were studied in mice with streptozotocin-induced and genetically determineddiabetes mellitus (9- to 12-week-old animals; streptozotocin was injected into 5-week-old mice). Recording of spinal cord dorsal surface potentials evoked by stimulation of the sciatic nerve showed that within the studied time interval the mice of the two diabetic groups were characterized by a moderate decrease (by 7.9% and 5.8%, on average) in the conduction velocity for afferent volleys (measured according to the delay of the peak of positivity of a volley) and by a considerable increase in the duration of the positive phase of these volleys (by 36% and 33%, respectively, as compared with the values in intact animals). Therefore, the population of relatively slow group A afferent fibers becomes noticeably larger in the sciatic nerve of diabetic mice even at early stages of the pathology, but at the same time a considerable amount of the fastest-conducting (about 45–60 m/sec) fibers is still preserved. The changes in mice with diabetes of different etiology were very similar, in spite of different hyperglycemia levels in these groups. Possible factors determining diabetes-induced modifications of the conduction velocity via the nerve fibers are discussed.Neirofiziologiya/Neurophysiology, Vol. 28, No. 4/5, pp. 173–178, July–October, 1996.     

The structure and nature of the macrophages participating in Wallerian degeneration of nerve fibers]

The nervus ischiadicus in white noninbred rats has been damaged by various means and then light- and electron-microscopically the sources of origin of macrophages, participating in removal of decay products in the distal part of the nerve have been studied. There is a close correlation between the process of Wallerian degeneration and aseptic inflammation. In the area of decay of the myelinated nervous fibers 4 types of cells have been identified and characterized. Three of them are precursors of macrophages, participating in removal of the myelin decay products: mononuclear cells of hematogenic origin, perineural cells, endoneural fibroblasts. The dynamics of these cells transformation into macrophages and into "foam cells" has been followed. The fourth type--Schwann cells; they do not directly participate in removal of the myelin decay products. They do not die, but, separating from the segments of the disintegrated myelin, dedifferentiate, proliferate and form cords, into which regenerating axons then grow in. To understand the role of various macrophages in the destructive and reparative processes, which develop in the nerves, is very important not only for searching definitive approaches in treatment of posttraumatic demyelinated processes, but for comprehending the mechanisms of certain autoimmune demyelinating diseases.