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PubMed2000

Autoantibodies to ganglionic acetylcholine receptors in autoimmune autonomic neuropathies.

BACKGROUND: Idiopathic autonomic neuropathy is a severe, subacute disorder with a presumed autoimmune basis. It is indistinguishable from the subacute autonomic neuropathy that may accompany lung cancer or other tumors. Autoantibodies specific for nicotinic acetylcholine receptors in the autonomic ganglia are potentially pathogenic and may serve as serologic markers of various forms of autoimmune autonomic neuropathy. METHODS: We tested serum from 157 patients with a variety of types of dysautonomia. Immunoprecipitation assays with iodine-125-labeled epibatidine and solubilized human neuroblastoma acetylcholine receptors were used to detect autoantibodies that bound to or blocked ganglionic receptors. RESULTS: Ganglionic-receptor-binding antibodies were found in 19 of 46 patients with idiopathic or paraneoplastic autonomic neuropathy (41 percent), in 6 of 67 patients with postural tachycardia syndrome, idiopathic gastrointestinal dysmotility, or diabetic autonomic neuropathy (9 percent), and in none of 44 patients with other autonomic disorders. High levels of the binding antibodies correlated with more severe autonomic dysfunction (including the presence of tonic pupils). Levels of these antibodies decreased in patients who had clinical improvement. All seven patients with ganglionic-receptor-blocking antibodies had ganglionic-receptor-binding antibodies and had idiopathic or paraneoplastic autonomic neuropathy. CONCLUSIONS: Seropositivity for antibodies that bind to or block ganglionic acetylcholine receptors identifies patients with various forms of autoimmune autonomic neuropathy and distinguishes these disorders from other types of dysautonomia. The positive correlation between high levels of ganglionic-receptor antibodies and the severity of autonomic dysfunction suggests that the antibodies have a pathogenic role in these types of neuropathy.

Adult↗

PubMed1977

Specific projection of displaced retinal ganglion cells upon the accessory optic system in the pigeon (Columbia livia).

In the pigeon, the nucleus of the basal optic root, a component of the accessory optic system, projects directly upon the vestibulo-cerebellum. This nucleus receives a prominent projection composed of large-diameter retinal axons, known as the basal optic root. The cells of origin of this tract were identified using horseradish peroxidase (donor:hydrogen-peroxide oxidoreductase, EC 1.11.1.7) as a retrograde marker. Injections of horseradish peroxidase confined primarily to the basal optic root nucleus labeled displaced ganglion cells of the contralateral retina. Cell sizes were 18-30 micronm and the dendrites of these cells were confined to the first stratum of the inner plexiform layer. Approximately 3700 displaced ganglion cells were labeled after injections of horseradish peroxidase into basal optic root. In contrast, no displaced ganglion cells were labeled after injections of horseradish peroxidase into the optic tectum, which labeled only cells in the ganglion cell layer proper. These findings indicate that displaced ganglion cells constitute a unique population of retinal neurons that give rise to a bisynaptic pathway directed to the cerebellum via the nucleus of the basal optic root. These displaced ganglion cells may play a major role inoculomotor reflexes.

Animals↗

PubMed1972

Polypeptide secretion from the isolated parietovisceral ganglion of Aplysia californica.

In vitro studies of the secretory behavior of the parietovisceral ganglion in Aplysia californica were performed. The aim of these studies was to investigate the release of polypeptides in response to depolarizing stimuli, and, in particular, to determine if a specific polypeptide known to induce egg laying in the intact animal is secreted into the bathing medium. During continuous perfusion of a ganglion preincubated in leucine-(3)H the application of either high-potassium medium or a burst of electrical stimuli (via the pleurovisceral connective nerve) evoked a marked increase in the amount of trichloroacetic acid (TCA)-precipitable radioactivity recovered in the perfusate. Enhanced release could be detected within 80 sec of the initial exposure to high potassium; however, incubation of a ganglion in calcium-free media before the application of high-potassium medium abolished the increase of precipitable radioactivity. Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis of perfusate samples revealed a significant change in the polypeptide species washed from the ganglion during high-potassium depolarization. Bioassays confirmed that egg laying is induced when high-potassium medium used to bathe a ganglion is injected into a recipient animal. These and other results permit the conclusion that the bulk of the polypeptide material secreted from the ganglion in response to depolarization is a specific neurohormone produced by two identified cell clusters, the so-called bag cells.

Acrylamides↗

PubMed2001

Adult rat otic placode-derived neurons and sensory epithelium express all four erbB receptors: a role in regulating vestibular ganglion neuron viability.

The erbB receptor family consists of erbB1/epidermal growth factor receptor, erbB2/neu, erbB3, and erbB4, all of which have been implicated in cell proliferation, differentiation, and survival in several tissues. In the nervous system, these family members can function in a trophic capacity for certain subpopulations of neurons and some types of non-neuronal cells. Vestibular sensory epithelial cells and vestibular ganglion neurons are derived from ectodermal otic placode and are essential components of the peripheral vestibular system, the sensory system for balance. Recent studies in mammals suggest that certain ligands of the epidermal growth factor receptor can induce proliferation of vestibular sensory epithelial cells. We now show that vestibular ganglion neurons and vestibular sensory epithelial cells express all four erbB receptors in adult rats. Cultured vestibular ganglion neurons also expressed all four erbB family members and were therefore used to analyze the effects of modulating erbB signaling on differentiated vestibular ganglion neurons. Transforming growth factor-alpha (a ligand for epidermal growth factor receptor) and sensory and motor neuron-derived factor (a ligand for erbB3 and erbB4) promoted vestibular ganglion neuron viability, whereas epidermal growth factor (another ligand for epidermal growth factor receptor) did not. Glial growth factor 2 (another ligand for erbB3 and erbB4) and an antibody that blocks erbB2/neu-mediated signaling inhibited vestibular ganglion neuron viability. Collectively, these observations indicate that erbB signaling regulates the viability of differentiated otic placode-derived cells in mammals and suggest that exogenous modulation of erbB signaling in peripheral vestibular tissues may prove therapeutically useful in peripheral vestibular disorders.

Animals↗

PubMed1983

Effect of parasympathetic decentralization and paracervical ganglion excision on reproductive function in the rat.

The uterine paracervical ganglion (Frankenhauser's ganglion) contains the terminal ganglion cells of the sacral parasympathetic system and, in some species, the short adrenergic system. Histochemical studies also show numerous chromaffin cells with morphologic attributes of interneurons. The present study explores the function of cell types present in this ganglion, by seeking changes in reproductive function following either parasympathetic decentralization (transection of the cauda equina) or excision of the ganglion itself. Two well-known reproductive phenomena were observed after each surgical intervention, namely, induction of uterine hyperemia by estrogen administration, and maintenance of normal vaginal cycles. Estrogen-induced uterine hyperemia was not affected by parasympathetic decentralization or ganglion excision. Therefore, nerves originating in, or passing through this structure may be eliminated as components of the vascular control mechanism. In contrast, compared to sham-operated controls, ganglionectomy caused a significant reduction in the proportion of animals exhibiting normal vaginal cycles postoperatively (P less than 0.05). Cycle distribution was more evident in animals ganglionectomized on metestrus (P less than 0.01) and proestrus (P less than 0.05) than in animals ganglionectomized on diestrus or estrus. Since parasympathetic decentralization did not produce cycle disruption similar to ganglionectomy, one may conclude that the cycle-modulating effect does not involve preganglionic fibers of the sacral parasympathetic nerves.

Animals↗

PubMed1982

The effects of halothane on sympathetic ganglionic transmission.

The effects of halothane on ganglionic transmission were studied in the stellate ganglion of the guinea pig using intracellular recordings in vitro. Depression of synaptic transmission is one of the actions common to many general anesthetics. The aim of this study was to investigate which of the processes involved in synaptic transmission are affected by halothane in concentrations comparable to those used during surgical anesthesia. The neurons of the stellate ganglion were depolarized using preganglionic nerve stimulation, postganglionic nerve stimulation, and intracellular stimulation before ad after introduction of halothane (vaporizer settings of 0.75% and 1.5% produced bath concentrations of 8 and 18 mg/dl, respectively). Halothane at both concentrations depressed sympathetic ganglionic transmission which was induced by stimulation of preganglionic nerves. Axonal transmission and the excitability of the postganglionic neurons to direct intracellular stimulation was far less sensitive to halothane than synaptic transmission. The depression of ganglionic transmission seen in the present study was most likely due to a decrease in transmitter release although alterations in postsynaptic receptor properties could have been involved as well. The decrease in sympathetic activity resulting from depression of ganglionic transmission probably contributes to the arterial hypotension seen during halothane anesthesia, along with direct myocardial depression, inhibition of catecholamine release from the adrenal medulla, direct action on vascular smooth muscle, and central sympathetic depression.

Action Potentials↗

PubMed2000

Stereospecific interaction of ketamine with nicotinic acetylcholine receptors in human sympathetic ganglion-like SH-SY5Y cells.

BACKGROUND: Surprising clinical evidence suggests a block of sympathetic transmission by ketamine. The action of ketamine on nicotinic acetylcholine receptors (nAChRs) in human ganglions is unknown. Because ganglionic transmission depends on nAChRs, such information may help to clarify whether ketamine impairs ganglionic transmission in men. Because racemic ketamine as well as S(+)-ketamine are used clinically, the authors investigated stereospecific effects on human ganglionic nAChRs. Stereospecific psychomimetic effects have been attributed to voltage-dependent Kv channel inhibition; therefore the effects on nAChRs were compared with those on Kv channels present in the same cells. METHODS: Whole-cell currents through nAChRs and K channels were measured in SH-SY5Y cells with the patch-clamp technique by application of acetylcholine (1 mm, nAChRs) or by a step depolarization from a holding potential of -80 mV to +40 mV (K channels). Electrolyte conditions were identical for both currents. RESULTS: Racemic ketamine and the isomers inhibited nAChRs and K channels in a concentration-dependent and reversible manner. Racemic ketamine inhibited nAChRs and K channels, with the anesthetic concentration inducing the half-maximal effect being 1.4 and 300 micrometer, respectively. Only inhibition of the nAChRs was stereoselective. The half-maximal concentrations were 0.8 and 3.6 micrometer for S(+)- and R(-)-ketamine. The K channels were 350 and 70 times less sensitive to the effects of S(+)- and R(-)-ketamine. CONCLUSION: Ketamine at concentrations found during clinical anesthesia exerts stereospecific effects on human ganglionic nAChRs but not on voltage-dependent K channels. Our results support the view that ketamine impairs sympathetic ganglionic transmission. Nonspecific effects on voltage-dependent K channels may underlie psychomimetic side effects.

Anesthetics, Dissociative↗

PubMed2002

Exposure of the dorsal root ganglion in rats to pulsed radiofrequency currents activates dorsal horn lamina I and II neurons.

OBJECTIVE: Application of pulsed radiofrequency (RF) currents to the dorsal ganglion has been reported to produce long-term relief of spinal pain without causing thermal ablation. The present study was undertaken to identify spinal cord neurons activated by exposure of the dorsal ganglion to pulsed RF currents in rats. METHODS: Left-sided hemilaminectomy was performed in adult Sprague-Dawley rats to expose the C6 dorsal root ganglion. An RF electrode (0.5 mm diameter) with a thermocouple for temperature monitoring was positioned on the exposed ganglion, and rats were assigned to one of three treatment groups: pulsed RF treatment (20 ms of 500-kHz RF pulses delivered at a rate of 2 Hz for 120 s to produce tissue heated to 38 degrees C), continuous RF (continuous RF currents for 120 s to produce tissue heated to 38 degrees C), or sham treatment (no RF current; electrode maintained in contact with ganglion for 120 s). RESULTS: Treatment with pulsed RF but not continuous RF was associated with a significant increase in the number of cFOS-immunoreactive neurons in the superficial laminae of the dorsal horn as observed 3 hours after treatment. CONCLUSION: Exposure of the dorsal ganglion to pulsed RF currents activates pain-processing neurons in the dorsal horn. This effect is not mediated by tissue heating.

Animals↗

PubMed1996

Changes in responses of wide dynamic range neurons in the spinal dorsal horn after dorsal root or dorsal root ganglion compression.

STUDY DESIGN: The electrophysiologic responses of wide dynamic range neurons in the spinal dorsal horn by compression of the dorsal root or of the dorsal root ganglion were investigated. OBJECTIVES: This study identified differences between the compression of the dorsal root against the compression of the dorsal root ganglion by examining the responses of wide dynamic range neurons. SUMMARY OF BACKGROUND DATA: The wide dynamic range neurons studied were known to be excited by primary afferent fibers, not only combined A delta and C-nociceptive fibers but also low threshold mechanoreceptive A beta fibers and A delta fibers of down hairs. Thus, the wide dynamic range neurons are classified as nociceptive neurons. METHODS: Extracellular activities of 32 wide dynamic range neurons were recorded from the laminae 4-6 of the seventh lumbar cord in anesthetized cats. A microvessel clip (40 g) was applied to compress the dorsal root or the dorsal root ganglion. RESULTS: Dorsal root compression produced only an initial burst (about 10-40 seconds). Prolonged repetitive firings were rarely maintained. In contrast, dorsal root ganglion compression resulted in a maintained repetitive firing throughout the period of compression. After release of compression of the dorsal root and the dorsal root ganglion, responses to brushing were facilitated, and the low threshold center of the receptive field expanded. CONCLUSIONS: These findings are consistent with the previous report that the radicular pain associated with a herniated intervertebral disc initially results from compression of the dorsal root ganglion.

Animals↗

PubMed2000

Herniated lumbar disc material as a source of free glutamate available to affect pain signals through the dorsal root ganglion.

STUDY DESIGN: Combined prospective human cohort and prospective controlled animal model. OBJECTIVES: To determine whether free glutamate is available in herniated disc material in concentrations sufficient to diffuse to glutamate receptors and affect the activity of neurons in the dorsal root ganglion that may transmit pain information. SUMMARY OF BACKGROUND DATA: The severity of lumbar radicular pain cannot be fully explained by physical pressure on nerve roots or ganglions. In experimental models, inflammatory processes are relatively modest under conditions of disc herniation. The hypothesis for the current study was that the proteoglycan link and core proteins, which contain high fractions of acidic amino acids, may be a source of glutamate when enzymatically degraded in an environment without glutamate reuptake systems. Glutamate would be free to diffuse to the dorsal root ganglion to affect glutamate receptors. METHODS: Disc material was harvested during surgery from herniated and nonherniated portions in patients undergoing elective lumbar disc surgery and subjected to immunohistochemistry and high-performance liquid chromatography for assessment of the presence of extracellular disc matrix glutamate. Miniosmotic pumps with differing concentrations of radiolabeled glutamate based on human data were implanted in the rat epidural space for 72 hours and dorsal root ganglion (DRG) in the region were harvested. RESULTS: Densitometry of disc matrix demonstrated immunohistochemical evidence for significant extracellular glutamate (P < 0.002). High performance liquid chromatography showed significant concentrations of glutamate in disc material and significantly more in herniated than in nonherniated disc material (P < 0.05). Significant radiolabeling of the dorsal root ganglion after epidural glutamate infusion was found at concentrations two orders of magnitude below measured disc glutamate levels. Autoradiography demonstrated radiolabeling of adjacent DRG. CONCLUSIONS: Glutamate originating from degenerated disc proteoglycan may diffuse to the dorsal root ganglion and effect glutamate receptors. Consideration may be given to treating disc radiculopathy with epidural glutamate receptor antagonists.

Adult↗

PubMed2001

Effect of nucleus pulposus on the neural activity of dorsal root ganglion.

STUDY DESIGN: This study was designed to investigate, using neurophysiologic techniques in an in vivo rat model, the effect of application of nucleus pulposus to the nerve root on the neural activity of the dorsal root ganglion and the corresponding receptive fields. OBJECTIVES: To assess a further role of the dorsal root ganglion in mechanisms of radicular pain in lumbar disc herniation. SUMMARY OF BACKGROUND DATA: It has been suggested that the epidural application of autologous nucleus pulposus without mechanical compression causes nerve root inflammation and related radicular pain in lumbar disc herniation. Concerning the dorsal root ganglion, its mechanical hypersensitivity and potential for generating ectopic discharges have been reported. However, the effect of autologous nucleus pulposus on the dorsal root ganglion is uncertain. METHODS: In adult Sprague-Dawley rats spontaneous neural activity was recorded from the surgically exposed L5 dorsal root using electrophysiologic techniques, and the mechanosensitivity of L5 dorsal root ganglia and corresponding receptive fields on the hind paw were measured using calibrated nylon filaments. Autologous nucleus pulposus from the tail or fat was implanted at the L5 nerve root. Neural activity was monitored for 6 hours. RESULTS: Spontaneous neural activity in the nucleus pulposus group gradually increased and showed significant differences compared with the fat group from 2.5 to 6 hours after exposure. The mechanosensitivity of the dorsal root ganglia showed significant increases compared with the fat group. CONCLUSIONS: After application of nucleus pulposus to the nerve root, the dorsal root ganglion demonstrated increased excitability and mechanical hypersensitivity. These results suggest that nucleus pulposus causes excitatory changes in the dorsal root ganglion.

Animals↗

PubMed2006

Substance P-saporin down-regulates substance P receptor immunoreactive sensory dorsal root ganglion neurons innervating the lumbar intervertebral discs in rats.

STUDY DESIGN: To examine changes in substance P receptors on dorsal root ganglion cells innervating the rat lumbar intervertebral discs using immunohistochemistry and a retrograde neurotracing method. OBJECTIVE: We evaluated the effects of intradiscal administration of substance P-saporin, a toxin selective for cells expressing substance P receptors. SUMMARY OF BACKGROUND DATA: The rat L5/6 intervertebral disc is multi-segmentally innervated from the L1-L6 dorsal root ganglions. Substance P and the neurokinin-1 receptor contribute to inflammatory pain transmission. Substance P immunoreactive-sensory nerve fibers in human intervertebral discs and immunoreactive-dorsal root ganglion neurons innervating rat intervertebral discs have been reported to be important in the transmission of discogenic low back pain. In the current study, we evaluated the effects of intradiscal administration of substance P-saporin, a toxin selective for cells expressing substance P receptor. METHODS: Sixteen rats were used (control group, n = 8; substance P-saporin group, n = 8). To detect dorsal root ganglion neurons innervating the L5/6 intervertebral disc, neurotracer (fluoro-gold crystals) was placed into the intervertebral disc. Seven days after fluoro-gold application, the L5/6 intervertebral disc was exposed and injected with 175 ng of sterile substance P-saporin (substance P-saporin group, n = 8). Fourteen days after the first operation, each dorsal root ganglion was harvested, sectioned, and processed for neurokinin-1 immunohistochemistry using rabbit antibody to neurokinin-1. The numbers of fluoro-gold labeled neurons, and fluoro-gold labeled and neurokinin-1 immunoreactive neurons were counted in both groups. RESULTS: Neurons innervating the L5/6 intervertebral discs, retrogradely labeled with fluoro-gold, were distributed throughout dorsal root ganglions from L1 to L6 in both groups. Of fluoro-gold labeled neurons, the proportion of neurokinin-1 immunoreactive neurons was 35% in the control group. However, the proportion of neurokinin-1 immunoreactive neurons was 8% after administration of substance P-saporin into the intervertebral discs (substance P-saporin group). Substance P-saporin significantly decreased the ratio of neurokinin-1 immunoreactive neurons. CONCLUSION: Substance P-saporin decreased the ratio of neurokinin-1 immunoreactive neurons innervating the disc related to discogenic low back pain. Substance P-saporin may be a useful tool to investigate the mechanism of discogenic low back pain.

Animals↗

PubMed1976

Transmission of signals from photoreceptors to ganglion cells in the eye of the turtle.

Synaptic transfer between receptors and ganglion cells was studied in the retina of the turtle. In the normal operation of this pathway, signals are relayed across two or more chemical synapses. Previous work indicates that the receptors give graded hyperpolarization to light, and that the bipolar cells also respond with graded potential changes; the ganglion cells give impulses. Injection of weak electrical currents into a single receptor provides an alternative means of activating the pathway. We have used this technique to examine (1) the role of the receptors' hyperpolarization in signal transmission and (2) the sensitivity and temporal properties of the pathway. The response of a ganglion cell evoked by light on the retina can be duplicated by electrically hyperpolarizing a receptor and antagonized by electrical depolarization. This indicates that the hyperpolarization is responsible for regulating the flow of information from the receptors to the second-order retinal cells. The sensitivity of the synaptic path from cones to ganglion cells, determined from electrical stimulation of single receptors, was found to be sufficient to permit detection of about 100 photoisomerizations. Using the same technique, the kinetics of transfer were studied and found to exhibit a delay or integrating process and also a slow differentiation that blocks steady-state transmission. For the path from red-sensitive cones to ganglion cells, the apparent time constant of the delay process was of the order of 75 ms and that of the differentiation, about 100 ms. In the path from rods to ganglion cells, the differentiation was several times slower.

Animals↗

PubMed1990

Ganglion cells in colonic mucosa.

Intramucosal ganglion cells are commonly believed not to occur in normal colon and to be found only in the chronic bowel motility disorder, neuronal intestinal dysplasia. After chance observations of two intramucosal ganglion cells in endoscopic biopsies in two patients without neuronal intestinal dysplasia, a retrospective study was undertaken to determine how frequently ganglion cells are present in colonic mucosa. Excluding the index cases, three intramucosal ganglion cells were found in 169 consecutive colonic biopsies. The nature of the ganglion cells was confirmed by positive neurone specific enolase staining by the peroxidase-antiperoxidase technique in all cases. None of the patients had neuronal intestinal dysplasia. The diagnosis of neuronal intestinal dysplasia should rely on a constellation of clinicopathological features. Rare intramucosal ganglion cells are a normal histological finding.

Adolescent↗

PubMed2004

Morphological features of chick retinal ganglion cells.

On average, in chicks, the total number of retinal ganglion cells is 4.9 x 10(6) and the cell density is 10400 cells/mm2. Two high-density areas, namely the central area (CA) and the dorsal area (DA), are located in the central and dorsal retinas, respectively, in post-hatching day 8 (P8) chicks (19000 cells/mm2 in the CA; 12800 cells/mm2 in the DA). Thirty percent of total cells in the ganglion cell layer are resistant to axotomy of the optic nerve. The distribution of the axotomy resistant cells shows two high-density areas in the central and dorsal retinas, corresponding to the CA (5800 cells/mm2) and DA (3200 cells/mm2). The number of presumptive ganglion cells in P8 chicks is estimated to be 4 x 10(6) (8600 cells/mm2 on average) and the density is 13500 and 10200 cells/mm2 in the CA and DA, respectively, and 4300 cell/mm2 in the temporal periphery (TP). The somal area of presumptive ganglion cells is small in the CA and DA (mean (+/- SD) 35.7 +/- 9.1 and 40.0 +/- 11.3 microm2, respectively) and their size increases towards the periphery (63.4 +/- 29.7 microm2 in the TP), accompanied by a decrease in cell density. Chick ganglion cells are classified according to dendritic field, somal size and branching density of the dendrites as follows: group Ic, Is, IIc, IIs, Ills, IVc. The density of branching points of dendrites is approximately 10-fold higher in the complex type (c) than in the simple type (s) in each group. The chick inner plexiform layer is divided into eight sublayers according to the dendritic strata of retinal ganglion cells and 26 stratification patterns are discriminated.

Animals↗

PubMed1989

Is the capacity for optic nerve regeneration related to continued retinal ganglion cell production in the frog?

In the central nervous system of fish and frogs, some, but not all, axons can regenerate. Retinal ganglion cells are among those that can. The retinae of fish and frogs produce new retinal neurons, including ganglion cells, for months or years after hatching. We have evaluated the hypothesis that retinal axonal regeneration is obligatorily linked to continued production of new ganglion cells. We used bromodeoxyuridine immunocytochemistry to assess retinal neurogenesis in juvenile, yearling, and 10 year old Xenopus laevis. Retinal ganglion cell genesis was vigorous in the marginal retina of the juveniles, but in the yearlings and the 10 year olds, no new ganglion cells were produced there. Cellular proliferation in the central retina was evident at all three ages, but none of the cells produced centrally were in the ganglion cell layer. Regeneration was examined in vivo by cutting one optic nerve and then, weeks later, injecting the eye with tritiated proline. Autoradiographs of brain sections showed that the optic nerves of all three ages regenerated. Regeneration in vitro was assessed using retinal explants from frogs of all three ages. In all cases, the cultures produced neurites, with some age-specific differences in the patterns of outgrowth. We conclude that retinal axonal regeneration is not linked obligatorily to maintained neurogenesis.

Journal Article↗

PubMed1987

Retrograde transport of endogenous nerve growth factor in superior cervical ganglion of adult rats.

The concentration of naturally synthesized nerve growth factor (NGF) was measured in various tissues of adult rats, using a highly sensitive two-site enzyme immunoassay. The highest concentration was found in the superior cervical sympathetic ganglion (SCG). Transection of the postganglionic external carotid nerve (ECN) reduced the ganglionic level of NGF more than did section of the internal carotid nerve (ICN). When both the preganglionic nerve and the ECN were cut, the ganglionic NGF level decreased even more. On the other hand, when the preganglionic nerve and the ICN were both sectioned, leaving the ECN intact, endogenous NGF content in the SCG was significantly enhanced 3-9 h after operation. Bilateral extirpation of submaxillary gland produced a rapid decrease in ganglionic NGF 3-6 h after operation, and even unilateral removal of one salivary gland caused a decrease in both ganglia, which was however much greater in the ipsi- than in the contralateral ganglion. Removal of the eyeballs caused a much smaller reduction in ganglionic NGF than did removal of the glands. These results suggest that the endogenous NGF that accumulates in the SCG is mostly synthesized in the submaxillary gland rather than in the iris, and that it is transported to the SCG, mostly via the ipsilateral ECN.

Animals↗

PubMed1998

Quantitative relationships between taste bud development and gustatory ganglion cells.

To determine whether patterns of taste bud innervation change during postnatal rat development, the number of geniculate ganglion cells that innervate single taste buds were quantified in adult and developing rats. While there was a large variation in numbers of ganglion cells that innervate individual taste buds, there was a high degree of organization in the system. Namely, the number of labeled geniculate ganglion cells innervating a taste bud was highly correlated with the size of the taste bud. This relationship between taste bud size and number of innervating ganglion cells develops over a prolonged postnatal period and is not established until postnatal day 40 (P40), when taste buds reach their adult size. In a second series of experiments, we sought to determine whether neural rearrangement of chorda tympani neurons is responsible for the development of this relationship by double-labeling single taste buds at different ages. We found that the number of ganglion cells innervating individual taste buds on P10 predicts the size that taste buds become by P40. This finding suggests that neural rearrangement is not responsible for establishing the relationship between taste bud size and the number of innervating ganglion cells during development. More importantly, it strongly suggests that the 'neural template' for the mature innervation pattern is determined during early postnatal development.

Animals↗