Properties of dorsal root unmedullated fibers on the two sides of the ganglion

As an aid in the interpretation of the physiological properties of unmedullated nerve fibers, particularly those having their cells of origin in the dorsal root ganglia, more precise information about their morphology has been acquired through employment of the electron microscope. The appearance of the fibers in the skin nerves is described, with special reference to the structure of their sheaths; and a notation is made about the bearing of the axon-sheath relationship on the biophysical mechanism of conduction (p. 714). There is no basic difference between the sheath systems of the d.r.C and the s.C fibers. Attention is called to a point of similarity between the sheaths of unmyelinated and myelinated axons (p. 715). An assessment was made of the likelihood of interaction between the fibers. In action potentials showing temporal dispersion at several distances, the elevations appeared in their calculated positions. A model of a group of Schwann sheaths was constructed from successive electron microscope sections, showing that the lengths of the sheath branches are short in comparison with the wave lengths of the action potentials. Supported by these and other considerations, the argument is strongly in favor of the conclusion that among d.r.C fibers, as in other fibers, there is no cross-excitation between the axons. A new analysis of the size distribution of the fibers in a sural nerve was made from electron microscope pictures; and from the measurements the action potential was constructed. The result confirmed the view, previously expressed, that the velocities of conduction in the fibers can be precisely accounted for by multiplying the diameters by a constant. In the dorsal roots, the striking change that takes place in the appearance of the fibers and their disposition in the Schwann sheaths can be seen in Fig. 11. The axons partake of the special properties of the peripheral branches, which necessitated the creation of the subdivision of d.r.C fibers. But, their diameters are much smaller. At a set of reduced conduction velocities the configuration of the compound action potential in the nerves is repeated in the roots, with the root velocities still conforming to the size-velocity rule derived from nerve axons.     

The postspike positivity of unmedullated fibers of dorsal root origin

The positivity following the spike in the action potential of unmedullated nerve fibers of dorsal root origin (d.r.C) has been shown to be homologous with the first positive potential (P₁) of other varieties of nerve fibers. Thus it is only through the large size of the positivity that this group of nerve fibers is set apart from other groups. New findings accentuate and make more explicit the difference of d.r.C fiber behavior from that of the sympathetic unmedullated fibers. Support of the conclusion is derived from re-examination of the A fibers as well as from observations on the d.r.C fibers. Increase in size of the P₁'s in a tetanus of the d.r.C fibers can occur if the frequency is high enough; and it does not occur in an A fiber tetanus if the frequency is low enough. Frequency is also critical in the obtainment of increasing P₁'s in a tetanus of sympathetic C fibers. Decrease in the size of the P₁'s in the course of a tetanus is attributable to development of the negative after-potential (N a-p). In rested d.r.C fibers the N a-p is latent. But it appears during a tetanus, develops in size, and after the tetanus leads to a long lasting and clearly defined second positive potential. Absence of a supernormal period during the N a-p of the d.r.C fibers is accounted for. An analysis is made of the apparent increase in size of the spike elevations during a tetanus, for the two subgroups of the C fibers. The difference between the after-potentials of A fibers and of sympathetic C fibers is correlated with the shapes of the curves of cathodal electrotonus of these fibers.     

Olfactory nerve fibers

Cross sections of olfactory nerves present a unique appearance. They indicate the presence of large numbers of very small nerve fibers, with a modal diameter of about 0.2 µ and a narrow range for their size variation. From one side of the nasal septum of a pig the yield of fibers was estimated at 6,000,000; the number arising from the turbinates would be considerably larger. The fibers are attached to the membranes of the Schwann sheaths in large bundles through mesaxons longer and more branched than those that have been seen in other nerves. Continuity of the axons between the nerves and the bipolar cells was traced in an examination of the olfactory mucous membrane; and the indication of a one-to-one relationship between cells and axons was reinforced by a comparative count. After the axons leave the bipolar cells they become incased in the central projections of the sustentacular cells. Where the latter come into contact with the basal cells the axons emerge to push back the plasma membranes of the basal cells in the first step in acquiring their nerve sheaths. Later steps are described. When the axons are delivered by the basal cells to the collecting Schwann tubes, they are already aggregated into small bundles with sheaths fundamentally the same as those they will possess until they are delivered to the glia in the olfactory bulb. Some of the aspects of the cytology of the bipolar cells and adjoining sustentacular cells are described. A survey of the physiological properties of olfactory nerve fibers was made in some experiments on the olfactory nerve of the pike. Almost all of the action potential is encompassed within a single elevation, manifesting at its front a conduction velocity of 0.2 m./sec. For a comparison, the last elevation in the C action potential in the sciatic nerve of the frog is cited as an example of conduction at the same velocity. Though expressed through long time constants, the properties of the pike olfactory fibers conform to the generalized schema for properties of vertebrate nerve fibers. This conformity signalizes that they differ from the exceptional properties of the unmedullated fibers of dorsal root origin. An afferent function for unmedullated nerve fibers does not imply that the fibers concerned are alike in their physiological properties.     

Conducting pathways of the dog solar plexus

Conducting pathways of the dog solar plexus were studied by recording action potentials from its nerves. The splanchnic nerves are composed of two groups of fast-conducting afferent A fibers (with conduction velocities of 12–15 and 25–56 m/sec), slowly conducting afferent C fibers (0.4–2.0 m/sec), and preganglionic B and C fibers (1.0–12.0 m/sec). Afferent A and C fibers from peripheral nerves run without interruption through the ganglia of the solar plexus, splanchnic nerves, and sympathetic chain and they enter the spinal cord in the composition of the dorsal roots. Cell bodies of A fibers are located in the spinal ganglia, those of the C fibers below the ganglia of the solar plexus, evidently in the walls of the internal organs. Peripheral nerves contain A fibers only with very low conduction velocities (13–20 m/sec) and no fast-conducting A fibers (25–56 m/sec) were found. Preganglionic fibers terminate synaptically on neurons of the ganglia of the solar plexus whose axons run in the peripheral nerves to the internal organs. Synaptic pathways run from some peripheral nerves of the solar plexus into others through its ganglia; in all probability these pathways participate in peripheral reflex arcs.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 8, No. 1, pp. 76–83, January–February, 1976.     

Calretinin-immunoreactive nerves in the uterus, pelvic autonomic ganglia, lumbosacral dorsal root ganglia and lumbosacral spinal cord

Nerves containing the calcium-binding protein calretinin have been reported in several organs but not in female reproductive organs and associated ganglia. This study was undertaken to determine if nerves associated with the uterus contain calretinin and the source(s) of calretinin-synthesizing nerves in the rat (are they sensory, efferent, or both?). Calretinin-immunoreactive nerves were present in the uterine horns and cervix where they were associated with arteries, uterine smooth muscle, glands, and the epithelium. Calretinin-immunoreactive terminals were apposed to neurons in the paracervical ganglia; in addition, some postganglionic neurons in this ganglion were calretinin positive. Calretinin perikarya were present in the lumbosacral dorsal root ganglia, no-dose ganglia, and lumbosacral spinal cord. Retrograde axonal tracing, utilizing Fluorogold injected into the uterus or paracervical parasympathetic ganglia, revealed calretinin-positive/Fluorogold-labeled neurons in the dorsal root and nodose ganglia. Also, capsaicin treatment substantially reduced the calretinin-positive fibers in the uterus and pelvic ganglia, thus indicating the sensory nature of these fibers. The presence of calretinin immunoreactivity identifies a subset of nerves that are involved in innervation of the pelvic viscera and have origins from lumbosacral dorsal root ganglia and vagal nodose ganglia. Though the exact function of calretinin in these nerves is not currently known, calretinin is likely to play a role in calcium regulation and their function.     

Some physiological characteristics of myelinated and unmyelinated fibers with very low conduction velocity

The compound action potential arising in response to supramaximal stimulation of Aδ- or C-fibers of a cat cutaneous nerve (the saphenous nerve) was investigated by methods improving the signal/noise ratio in the record of the unit evoked response. By the use of optical and computer (BÉSM-3M) methods of coherent signal accumulation followed by averaging, potentials of nerve fibers ranging in amplitude from 20 to 0.05 µV and in duration from 10 to 0.4 msec were distinguished from the apparatus noise. A continuous distribution of nerve fibers by conduction velocity was found over the range from 80 to 0.15 m/sec. The conditions of appearance of low-amplitude action potentials of nerve fibers with a low conduction velocity are discussed.     

Attenuation of phrenic motor discharge by phrenic nerve afferents

Short latency phrenic motor responses to phrenic nerve stimulation were studied in anesthetized, paralyzed cats. Electrical stimulation (0.2 ms, 0.01-10 mA, 2 Hz) of the right C5 phrenic rootlet during inspiration consistently elicited a transient reduction in the phrenic motor discharge. This attenuation occurred bilaterally with an onset latency of 8-12 ms and a duration of 8-30 ms. Section of the ipsilateral C4-C6 dorsal roots abolished the response to stimulation, thereby confirming the involvement of phrenic nerve afferent activity. Stimulation of the left C5 phrenic rootlet or the right thoracic phrenic nerve usually elicited similar inhibitory responses. The difference in onset latency of responses to cervical vs. thoracic phrenic nerve stimulation indicates activation of group III afferents with a peripheral conduction velocity of approximately 10 m/s. A much shorter latency response (5 ms) was evoked ipsilaterally by thoracic phrenic nerve stimulation. Section of either the C5 or C6 dorsal root altered the ipsilateral response so that it resembled the longer latency contralateral response. The low-stimulus threshold and short latency for the ipsilateral response to thoracic phrenic nerve stimulation suggest that it involves larger diameter fibers. Decerebration, decerebellation, and transection of the dorsal columns at C2 do not abolish the inhibitory phrenic-to-phrenic reflex.     

两种软体动物神经系统一氧化氮合酶的组织化学定位

运用一氧化氮合酶(NOS)组织化学方法研究了软体动物门双壳纲种类中国蛤蜊和腹足纲种类嫁Qi神经系统中NOS阳性细胞以及阳性纤维的分布。结果表明：在蛤蜊脑神经节腹内侧,每侧约有10-15个细胞呈强NOS阳性反应,其突起也呈强阳性反应,并经脑足神经节进入足神经节的中央纤维网中;足神经节内只有2个细胞呈弱阳性反应,其突起较短,进入足神经节中央纤维网中,但足神经节中,来自脑神经节阳性细胞和外周神经系统的纤维大多呈NOS阳性反应;脏神经节的前内侧部和后外侧部各有一个阳性细胞团,其突起分别进入后闭壳肌水管后外套膜神经和脑脏神经索。脏神经节背侧小细胞层以及联系两侧小细胞层的纤维也呈NOS阳性反应。嫁Qi中枢神经系统各神经节中没有发现NOS阳性胞体存在;脑神经节、足神经节、侧神经节以及脑—侧、脑—足、侧—脏连索中均有反应程度不同的NOS阳性纤维,这些纤维均源于外周神经。与已研究的软体动物比较,嫁Qi和前鳃亚纲其它种类一样,神经系统中NO作为信息分子可能主要存在于感觉神经。而中国蛤蜊的神经系统中一氧化氮作为信息分子则可能参与更广泛的神经调节过程。     

Galanin-immunoreactive nerves in the female rat paracervical ganglion and uterine cervix: distribution and reaction to capsaicin

Summary The presence and distribution of galanin-immunoreactivity was examined in the uterine cervix and paracervical autonomic ganglia of the female rat. Some animals were treated with capsaicin to determine if galanin-immunoreactivity was present in small-diameter primary afferent nerves. Other animals were treated with the noradrenergic neurotoxin 6-hydroxydopamine to ascertain if galanin-immunoreactivity was present in sympathetic noradrenergic nerves. Galanin-immunoreactive nerve fibers were sparse in the cervical myometrium and vasculature, but numerous in the paracervical ganglion where they appeared to innervate principal neurons. Immunoreactivity was also present in dorsal root ganglia, dorsal horn of spinal cord, and inferior mesenteric ganglia. Capsaicin treatment resulted in a marked reduction of galanin-immunoreactivity in the spinal cord dorsal horn, but not in the dorsal root ganglia, paracervical ganglia, or cervix (although there was a substantial reduction of substance P-, neurokinin A-, and calcitonin gene-related peptide-immunoreactivity in the dorsal horn, dorsal root ganglia, and uterine cervix). 6-Hydroxydopamine treatment did not cause any appreciable change in the galanin-immunoreactivity in any tissues. We conclude that galanin-like immunoreactivity is expressed in nerve fibers innervating the paracervical ganglia and uterine cervix of the female rat. This immunoreactivity is probably present in afferent nerves and could play a role in neuroendocrine reflexes and in reproductive function.     

Distribution, origin and sensitivity to capsaicin of primary afferent substance P-immunoreactive nerves in the heart

This report is intended as an overview of the distribution, origin and sensitivity to capsaicin of substance P-immunoreactive (SP-I) primary afferent cardiac nerves. Immunohistochemical and physiological methods were employed to compare the presence and density of these nerve fibers in the guinea pig and rat hearts. SP-I fibers are numerous in the guinea pig heart including the parietal pericardium, atria, ventricles, valves, coronary arteries and around intrinsic cardiac ganglion cells. The rat heart contains few SP-I fibers. Vagotomy does not influence the number of intensity of immunoreactive fibers in the guinea pig heart. By stimulating the atrium or ventricle and recording from the second or third thoracic dorsal roots Ad1, Ad2 and C fibers were demonstrated in the atria, but only Ad fibers in the guinea pig ventricle; in addition, only Ad fibers were recorded from the vagus nerves. Only Ad1 fibers were demonstrated in the rat heart. Treatment with capsaicin depletes the SP-I and decreases the conduction velocity of C-fibers and some Ad2 fibers in the guinea pig heart. We suggest that SP-I primary afferent nerve fibers are unmyelinated (C-type) or small myelinated (Ad2-type) nerves in the guinea pig heart and that their cell bodies of origin are predominantly in dorsal root ganglia.     

Response characteristics of Herbst corpuscles in the interosseous region of the pigeon's hind limb

The Herbst corpuscle, found only in birds, is one of the morphologically distinct types of lamellated sensory nerve endings. Its response properties were studied electrophysiologically in anesthetized pigeons by recording from: (A) afferents emerging from single Herbst corpuscles located in the interosseous region of the shank, (B) from vibration-sensitive cells found in the dorsal root ganglia near the lumbosacral enlargement of the spinal cord, and (C) from nerve fibers dissected out of the sciatic nerve. Vibration-sensitive cells in the dorsal root ganglia and in sciatic nerve fibers exhibited properties that were very similar to those found at the Herbst corpuscle itself. All three recording approaches indicated that Herbst corpuscles are vibration-sensitive mechano-receptors with broad bandpass tuning curves. With all approaches, the lowest threshold always fell in the frequency range between 400 and 800 Hz. The value of the threshold, however, varied with the method, being as low as 0.08 m with method C and as high as 1 m with method A. Regardless of method, these neurons exhibited no spontaneous activity, and their firing displayed a special sensory coding pattern at high stimulus amplitude: the nerve impulses were phase locked to the stimulus cycle, exhibiting a 1:1 relationship with it up to a frequency of 500 Hz. Comparison of these data with prior behavioral data suggests that the Herbst corpuscle peripheral mechanoreceptors are part of a vibratory sensory system which acts as a warning device, given attentive behavior.Abbreviations AP action potential - INTH interspike interval histogram     

Synaptic transmission in thoracic autonomic ganglia of the dog

Afferent stimulation of one canine thoracic cardiopulmonary nerve can generate compound action potentials in another ipsilateral cardiopulmonary nerve. These compound action potentials persist after acute decentralization of the middle cervical ganglion, indicating that they result from neural activity in the middle cervical ganglion and thoracic nerves. Changing the frequency of stimulation can alter the compound action potentials, suggesting that temporal facilitation or inhibition occurs in this middle cervical ganglion preparation. The compound action potentials can be modified by stimulation of sympathetic preganglionic fibers and by hexamethonium, atropine, phentolamine, propranolol, and (or) manganese. It thus appears that afferent cardiopulmonary nerves can activate efferent cardiopulmonary nerves via synaptic mechanisms in the stellate and middle cervical ganglia. It also appears that these mechanisms involve adrenergic and cholinergic receptors and are influenced by preganglionic sympathetic fibers arising from the cord.     

Complete sciatic nerve transection induces increase of neuropeptide Y-like immunoreactivity in primary sensory neurons and spinal cord of frogs

Neuropeptide Y (NPY) was immunohistochemically investigated in the frog spinal cord and dorsal root ganglia after axotomy. In normal ganglia, moderate NPY-like immunoreactivity (NPY-IR) prevailed in large and medium cells. In the spinal cord, the NPY-IR was densest in the dorsal part of the lateral funiculus. Other fibers and neurons NPY-IR were observed in the dorsal and ventral terminal fields and mediolateral band. NPY-IR fibers were also found in the ventral horn and in the ventral and lateral funiculi. The sciatic nerve transection increased the NPY-IR in large and medium neurons of the ipsilateral and contralateral dorsal root ganglia at 3 and 7 days, but no clear change was found at 15 days. In the spinal cord, there was a bilateral increase in the NPY-IR of the dorsal part of the lateral funiculus. In the ipsilateral side, the NPY-IR was increased at 3 and 7 days but was decreased at 15 days. In the contralateral side, a significant reduction at 15 days occurred. These findings seem to favor the role of NPY in the modulation of pain-related information in frogs, suggesting that this role of NPY may have appeared early in vertebrate evolution.     

外周诱发电位的模型研究

本文根据容积导体中有关动作电位的电生理理论,用三点源模型模拟单根纤维动作电位(SFAP),并假设神经束的复合动作电位(CAP)是由SFAP线性叠加而成,给出了神经束CAP的模型.通过运用上述模型,计算了正常人正中神经纤维传导速度分布,分析了刺激腕部正中神经引导的传感诱发电位(SEP)的N~-_9成分;另外,还得出一些描述此外周传导通路性质的其它参数,如平均传导速度、神经纤维活动最可几传速度分布范围等.此方法可用来研究其它各种外围诱发电位.     

Distribution of five peptides, three general neuroendocrine markers, and two synaptic-vesicle-associated proteins in the spinal cord and dorsal root ganglia of the adult and newborn dog: an immunocytochemical study

This study describes the immunocytochemical distribution of five neuropeptides (calcitonin gene-related peptide [CGRP], enkephalin, galanin, somatostatin, and substance P), three neuronal markers (neurofilament triplet proteins, neuron-specific enolase [NSE], and protein gene product 9.5), and two synaptic-vesicle-associated proteins (synapsin I and synaptophysin) in the spinal cord and dorsal root ganglia of adult and newborn dogs. CGRP and substance P were the only peptides detectable at birth in the spinal cord; they were present within a small number of immunoreactive fibers concentrated in laminae I-II. CGRP immunoreactivity was also observed in motoneurons and in dorsal root ganglion cells. In adult animals, all peptides under study were localized to varicose fibers forming rich plexuses within laminae I-III and, to a lesser extent, lamina X and the intermediolateral cell columns. Some dorsal root ganglion neurons were CGRP- and/or substance P-immunoreactive. The other antigens were present in the spinal cord and dorsal root ganglia of both adult and newborn animals, with the exception of NSE, which, at birth, was not detectable in spinal cord neurons. Moreover, synapsin I/synaptophysin immunoreactivity, at birth, was restricted to laminae I-II, while in adult dogs, immunostaining was observed in terminal-like elements throughout the spinal neuropil. These results suggest that in the dog spinal cord and dorsal root ganglia, peptide-containing pathways complete their development during postnatal life, together with the full expression of NSE and synapsin I/synaptophysin immunoreactivities. In adulthood, peptide distribution is similar to that described in other mammals, although a relative absence of immunoreactive cell bodies was observed in the spinal cord.     

The Topography of the Superficial Roots and Ganglia of the Anterior Lateral Line Nerve of the Smooth Dogfish,Mustelus canis

The topographic relationships of the superficial roots and ganglia of the anterior lateral line nerve (NLLa) to each other and to cranial nerves V, VII and VIII were studied, in the smooth dogfish Mustelus canis, by dissection of Sudan Black Bstained specimens. NLLa consists of four branches: namely, superficial ophthalmic, buccal, otic and external mandibular. Each branch carries lateral line neurons exclusively and forms a dorsal root and a ventral root which enter the anterior lateral line lobe and posterior lateral line lobe of the medulla respectively. It is estimated that slightly more than 50% of the fibers of the superficial opthalmic, approximately 60% of the fibers of the buccal, at least 35% of the fibers of the otic and about 20% of the fibers of the external mandibular constitute the dorsal root. The ventral root is comprised of less than 50% of the fibers of the superficial ophthalmic, 40% of the fibers of the buccal, at least 50% of the fibers of the otic, and 80% of the fibers of the external mandibular. These results are correlated with the peripheral distribution and central termination of NLLa and it is concluded that the dorsal root carries axons from ampullary receptors and the ventral root carries fibers that innervate ordinary lateral line sense organs.     

大鼠脊神经节内交感神经支配的荧光组织化学与HRP示踪观察

本研究应用乙醛酸诱发儿茶酚胺（ＣＡ）荧光技术观察大鼠肾上腺素（ＮＡ）能神经在脊神经节内的分布;并应用ＨＲＰ顺、逆行追踪技术对脊神经节内ＮＡ能神经纤维的起源及其与脊神经节神经元的关系进行了探讨。荧光组织化学观察发现、有些神经节神经元胞体周围分布有带膨体的ＮＡ能神经末梢;有的紧密围绕脊神经节细胞——卫星细胞复合体。颈上交感神经节内注射霍乱毒素Ｂ亚单位结合ＨＲＰ（ＣＢ┐ＨＲＰ）,在同侧Ｃ３～６节段脊神经节内可见标记的点状纤维末梢紧邻于节细胞旁。Ｔ１１～Ｌ２节段脊神经节内注射ＨＲＰ后,在同侧椎旁交感链（Ｔ９～Ｌ１）内可见标记的交感节后神经元胞体。上述实验结果表明,交感节后神经元发出节后纤维可直接到达脊神经节内,与节细胞发生接触。本研究提示、交感神经在脊神经节水平可能参与躯体初级传入信息的调制     

Evidence for neuropeptide FF (FLFQRFamide) in rat dorsal root ganglia.

By using specific antibodies and radioimmunological and immunohistochemical methods, we here show that neuropeptide FF (NPFF) occurs in cervical and lumbar dorsal root ganglia cells. Levels in the ganglia were low because they were detectable only after colchicine treatment or after unilateral dorsal rhizotomy. Similar high-performance liquid chromatography profiles were obtained from dorsal root ganglia and spinal cord extracts, indicating that the NPFF-immunoreactivity in the dorsal root ganglia represented similar molecular forms to that in the spinal cord. Immunocytochemistry localized NPFF-immunoreactivity in small- and medium-sized cells. These data suggest that low levels of NPFF present in fine diameter primary afferent fibers could be involved in the treatment of nociceptive information from fore- or hindlimb.     

Uptake of Endoneurial Lipoprotein into Schwann Cells and Sensory Neurons Is Mediated by Low Density Lipoprotein Receptors and Stimulated After Axonal Injury

During Wallerian degeneration of rat sciatic nerve, the expression of apolipoprotein E increases and apolipoprotein E-containing endoneurial lipoproteins accumulate in the distal nerve segment. In established primary cultures dissociated from dorsal root ganglia, Schwann cells and sensory neurons internalized rhodamine-labeled lipoproteins isolated from crushed rat sciatic nerve as well as low density lipoprotein (LDL) from human serum. The uptake of endoneurial lipoproteins could be inhibited by an excess of LDL or at low temperature (4 degrees C). After transection of nerve fibers in dorsal root ganglia explant cultures, the uptake of lipoproteins was markedly stimulated in Schwann cells that were in close proximity to degenerating neurites. A specific monoclonal antibody directed to the bovine LDL receptor (clone C7) was shown to cross-react with LDL receptor preparations of rat endoneurial cells. LDL receptor immunoreactivity was expressed by cell bodies and processes of cultured Schwann cells, sensory neurons, and fibroblasts from dorsal root ganglia. Incubation of Schwann cells and neurons with the LDL receptor antibody strongly inhibited the uptake of endoneurial lipoproteins. Our results provide direct evidence for the important role of the LDL receptor-mediated pathway to internalize endoneurial lipoproteins into Schwann cells and peripheral neurons required for reuse of cholesterol and other lipids in myelin and plasma membrane biogenesis during nerve repair.