Increased intraepithelial innervation in women with vulvar vestibulitis syndrome

Women with vulvar vestibulitis syndrome (VVS) suffer from severe pain and discomfort in the area around the introitus at almost any stimulus that causes pressure within the vestibule. In spite of the severe sensory symptoms present in these women, the influence of the peripheral nerves in the vulvar vestibulum has not been clarified before. In this study the nerve supply in the vestibular mucosa in women with VVS and in healthy women free from vulvar symptoms has been revealed by PGP 9.5 immunohistochemistry. The results show a significant increase in the number of intraepithelial nerve endings in women with VVS, indicating an alteration in the nerve supply in the afflicted area.

Pathology of nerve terminal degeneration in the skin

To characterize the pathology of epidermal nerve degeneration and regeneration, we investigated temporal and spatial changes in skin innervation of the mouse footpad. Within 24 hours after sciatic nerve axotomy, terminals of epidermal nerves appeared swollen and there was a mild reduction in epidermal nerve density (5.7 +/- 2.8 vs 12.7 +/- 2.2 fibers/mm, p < 0.04). Epidermal nerves completely disappeared by 48 hours (0.2 +/- 0.2 vs 14.2 +/- 0.9 fibers/mm, p < 0.001). Concomitant with the disappearance of epidermal nerves, the immunocytochemical pattern of the subepidermal nerve plexus became fragmented. At the electron microscopic level, the axoplasm of degenerating dermal nerves was distended with organelles and later became amorphous. Beginning from day 28 after axotomy, collateral sprouts from the adjacent saphenous nerve territory extended into the denervated area with a beaded appearance. They never penetrated the epidermal-dermal junction to innervate the epidermis. In contrast, 3 months after nerve crushing, the epidermis on the surgery side resumed a normal innervation pattern as the epidermis on the control side (10.3 +/- 3.9 vs 10.6 +/- 1.5 fibers/mm, p = 0.1). This study demonstrates the characteristics of degenerating and regenerating nerves, and suggests that successful reinnervation mainly originates from regenerating nerves of the original nerve trunks. All these findings provide qualitative and quantitative information for interpreting the pathology of cutaneous nerves.

Induction of nitric oxide synthase activity in nucleus ambiguus motoneurons after injury to the rat recurrent laryngeal nerve

Recent studies have implicated nitric oxide (NO) in neuronal degeneration and plasticity in the motor nervous system. In the present study, we investigated the induction of nitric oxide synthase (NOS) in the motoneurons in the nucleus ambiguus (NA) after injury to the rat recurrent laryngeal nerve (RLN) using nicotinamide-adenine-dinucleotide-phosphate-diaphorase (NADPH-d) histochemistry. NADPH-d reactivity was clearly induced in motoneurons in the ipsilateral NA after transection or avulsion of the RLN, compared with control animals. This finding suggests that NO may play an important role in the pathogenesis of RLN paralysis. Another interesting finding in the present study was the induction of NADPH-d reactivity in nerve terminals of the NA after RLN injury. This finding suggests that RLN injury has some effect on nitrergic input to the NA and a direct effect on the motoneurons.

The neurotoxicity of the venom phospholipases A(2), notexin and taipoxin

The presynaptically active, toxic phospholipases known as notexin and taipoxin are principal components of the venom of the Australian tiger snake and the Australian taipan respectively. The inoculation of the toxins into one hind limb of rats caused, within 1 h, the depletion of transmitter from the motor nerve terminals of the soleus muscle. This was followed by the degeneration of the motor nerve terminals and of the axonal cytoskeleton. By 24 h 70% of muscle fibers were completely denervated. Regeneration and functional reinnervation were almost fully restored by 5 days, but collateral innervation was common in the regenerated muscles, and this abnormality persisted for at least 9 months. The data provide an explanation for both the severity of neuromuscular paralysis that can accompany envenoming bites by tiger snakes and taipans and the difficulty experienced by physicians in managing the envenomed subjects.

Time course of ultrastructural changes and immunoelectron microscopic localization of neurocalcin in motor endplates of the lumbrical muscles of rats given a single administration of 2,5-di(tert-butyl)-1,4-hydroquinone

A time-course study of ultrastructural changes and immunoelectron microscopic localization of neurocalcin was performed on motor endplates of the lumbrical muscles of female Wistar rats given a single oral administration of 2,5-di(tert-butyl)-1,4-hydroquinone (DTBHQ) at a dose of 120 mg/kg. Toxic signs such as salivation and muscle weakness of the hind legs appeared from 3 h after DTBHQ administration. No remarkable macroscopic or light microscopic changes were noted in the lumbrical muscles of the treated rats. At the ultrastructural level, neurotoxicity characterized by a decreases or loss of synaptic vesicles and mitochondria was observed after 24 h and at the 1-week time point, nerve endings had disappeared in some of the motor endplates, while many neurite nerve endings suggestive of early stage regeneration were apparent. After 6 weeks, newly formed reinnervated endplates were observed. Immunoelectron microscopically, the synaptic vesicle membranes were heavily labeled for neurocalcin in the control rats, but not at 24 h after DTBHQ treatment. Synaptic vesicle membranes in the DTBHQ group were weakly labeled at 1 week, but strongly at 6 weeks. The results strongly suggest that DTBHQ targets the motor endplates in the rat lumbrical muscles, causing depletion of neurocalcin in the synaptic vesicles followed by their loss.

Multiple types of calcium channels mediate transmitter release during functional recovery of botulinum toxin type A-poisoned mouse motor nerve terminals

The involvement of different types of voltage-dependent calcium channels in nerve-evoked release of neurotransmitter was studied during recovery from neuromuscular paralysis produced by botulinum toxin type A intoxication. For this purpose, a single subcutaneous injection of botulinum toxin (1 IU; DL50) on to the surface of the mouse levator auris longus muscle was performed. The muscles were removed at several time-points after injection (i.e. at one, two, three, four, five, six and 12 weeks). Using electrophysiological techniques, we studied the effect of different types of calcium channel blockers (nitrendipine, omega-conotoxin-GVIA and omega-agatoxin-IVA) on the quantal content of synaptic transmission elicited by nerve stimulation. Morphological analysis using the conventional silver impregnation technique was also made. During the first four weeks after intoxication, sprouts were found at 80% of motor nerve terminals, while at 12 weeks their number was decreased and the nerve terminals were enlarged. The L-type channel blocker nitrendipine (1 microM) inhibited neurotransmitter release by 80% and 30% at two and five weeks, respectively, while no effects were found at later times. The N-type channel blocker omega-conotoxin-GVIA (1 microM) inhibited neurotransmitter release by 50-70% in muscles studied at two to six weeks, respectively, and had no effect 12 weeks after intoxication. The P-type channel blocker omega-agatoxin-IVA (100 nM) strongly reduced nerve-evoked transmitter release (>90%) at all the time-points studied. Identified motor nerve terminals were also sensitive to both nitrendipine and omega-conotoxin-GVIA. This study shows that multiple voltage-dependent calcium channels were coupled to transmitter release during the period of sprouting and consolidation, suggesting that they may be involved in the nerve ending functional recovery process.

Cerebral amyloid induces aberrant axonal sprouting and ectopic terminal formation in amyloid precursor protein transgenic mice

A characteristic feature of Alzheimer's disease (AD) is the formation of amyloid plaques in the brain. Although this hallmark pathology has been well described, the biological effects of plaques are poorly understood. To study the effect of amyloid plaques on axons and neuronal connectivity, we have examined the axonal projections from the entorhinal cortex in aged amyloid precursor protein (APP) transgenic mice that exhibit cerebral amyloid deposition in plaques and vessels (APP23 mice). Here we report that entorhinal axons form dystrophic boutons around amyloid plaques in the entorhinal termination zone of the hippocampus. More importantly, entorhinal boutons were found associated with amyloid in ectopic locations within the hippocampus, the thalamus, white matter tracts, as well as surrounding vascular amyloid. Many of these ectopic entorhinal boutons were immunopositive for the growth-associated protein GAP-43 and showed light and electron microscopic characteristics of axonal terminals. Our findings suggest that (1) cerebral amyloid deposition has neurotropic effects and is the main cause of aberrant sprouting in AD brain; (2) the magnitude and significance of sprouting in AD have been underestimated; and (3) cerebral amyloid leads to the disruption of neuronal connectivity which, in turn, may significantly contribute to AD dementia.

Sprouting of dopaminergic axons after striatal injury: confirmation by markers not dependent on dopamine metabolism

Striatal injury increases dopamine metabolism in the nigrostriatal system but it is unclear whether this response is due to increased synthesis and activation of tyrosine hydroxylase within existing dopamine terminals and/or branching and sprouting of new terminals. While monitoring the density of tyrosine hydroxylase immunoreactive fibers suggests that sprouting occurs, this technique alone cannot adequately answer this question since the intensity of staining and thus the visibility of individual fibers are intimately linked to dopaminergic activity. However, by examining axons and their branches using markers that are independent of dopamine metabolism it is possible to determine whether dopaminergic sprouting does in fact take place. One month after using a Scouten wire knife to create a small lesion in the left striatum of normal C57/bl-6 mice, silver staining revealed an increase in the total number of neuronal fibers throughout the injured striatum. This was accompanied by intense staining of tyrosine hydroxylase-positive fibers around the wound and an increased density of striatal fibers labeled with dextran-biotin after injection of this neuronal tracer into the substantia nigra 1 month after striatal surgery and 5 days prior to sacrifice. The increase in tyrosine hydroxylase immunoreactivity confirms previous observations of increased dopaminergic activity after striatal injury. The increases in silver staining and dextran-biotin transport provide independent evidence that this increase in dopaminergic activity occurs because of sprouting of new fibers originating in the substantia nigra.

Paraquat elicited neurobehavioral syndrome caused by dopaminergic neuron loss

The herbicide paraquat, bearing structural similarity to the known dopaminergic neurotoxicant MPTP, has been suggested as a potential etiologic factor in Parkinson's disease. Consideration of paraquat as a candidate neurotoxicant requires demonstration that systemic delivery produces substantia nigra dopaminergic neuron loss and the attendant neurobehavioral syndrome reflecting depletion of dopamine terminals within the striatum. To address these issues paraquat was administered systemically into adult C57 bl/6 mice, ambulatory behavior monitored, substantia nigra dopamine neuron number and striatal dopamine terminal density quantified. The data indicate that paraquat like MPTP elicits a dose-dependent decrease in substantia nigra dopaminergic neurons assessed by a Fluoro-gold prelabeling method, a decline in striatal dopamine nerve terminal density assessed by measurement of tyrosine hydroxylase immunoreactivity; and neurobehavioral syndrome characterized by reduced ambulatory activity. Taken together, these data suggest that systemically absorbed paraquat crosses the blood-brain barrier to cause destruction of dopamine neurons in the substantia nigra, consequent reduction of dopaminergic innervation of the striatum and a neurobehavioral syndrome similar to the well characterized and bona fide dopaminergic toxin MPTP.

Regional and temporal expression of the peripheral benzodiazepine receptor in MPTP neurotoxicity

We used the dopaminergic neurotoxicant 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to evaluate the sensitivity and specificity of the peripheral benzodiazepine receptor (PBR) as a biomarker of chemical-induced neurotoxicity. Receptor autoradiography of [3H]-PK11195, a PBR selective ligand, indicated dose-dependent increases throughout the nigrostriatal dopaminergic system as early as 24 h after MPTP administration (10-80 mg/kg), which persisted for at least 21 days. The binding of [3H]-PK11195 was increased as much as 98% in the corpus striatum and 114% in the substantia nigra, following MPTP exposure. The integrity of nigrostriatal dopaminergic terminals in the corpus striatum was assessed by measuring high affinity dopamine transporter (DAT) levels and dopamine content. DAT levels were measured by [3H]-WIN 35,428 autoradiography, and dopamine content decreased with increasing MPTP dose. Reductions of both indices of dopaminergic terminal integrity correlated with increased levels of [3H]-PK11195-binding in the striatum (r2 = 0.84 for DAT and 0.93 for dopamine content). Tyrosine hydroxylase (TH) immunohistochemistry demonstrated dose-dependent reductions of dopaminergic neurons in the substantia nigra pars compacta, with a 67% loss measured 7 days after treatment with 80 mg/kg MPTP. The loss of TH-positive neurons was correlated (r2 = 0.95) with increased levels of [3H]-PK11195 binding in the substantia nigra. These findings demonstrate that the PBR is both sensitive and specific for identifying brain regions involved in MPTP neurotoxicity.

Inactivity-induced remodeling of neuromuscular junctions in rat diaphragmatic muscle

We hypothesized that inactivity-induced remodeling of neuromuscular junctions (NMJs) depends on fiber type and the match between muscle fiber and motoneuron (MN) activities. Two inactivity models were studied in rat diaphragmatic muscle: spinal hemisection at C2 (SH), where both diaphragmatic muscle fibers and phrenic MNs were inactive, and tetrodotoxin (TTX) nerve blockade, where only muscle fibers were inactive. After 2 weeks of inactivity, there was increased number of pre- and postsynaptic branches (fragmentation) of NMJs at type IIx/b fibers in both models. In addition, planar NMJ areas at type IIx/b fibers in the SH model were enlarged. In contrast, NMJs at type I and IIa fibers were unaffected in both SH and TTX models. Functionally, neuromuscular transmission in diaphragmatic muscle fibers improved in the SH model, but worsened in the TTX model, compared to controls. These results suggest that NMJ remodeling depends on the level of MN activity. The relative preservation of NMJs at type I and IIa fibers suggests a potential for recovery from diaphragmatic paralysis in the clinical setting, at least for respiratory behaviors.

Morphological changes in periodontal mechanoreceptors of mouse maxillary incisors after the experimental induction of anterior crossbite: a light and electron microscopic observation using immunohistochemistry for PGP 9.5

Ruffini nerve endings (mechanoreceptors) in the periodontal ligament (PDL) of mouse incisors were examined to elucidate whether experimentally-induced crossbites cause any changes or abnormalities in their morphology and distribution. Anterior guiding planes were attached to the mandibular incisors of 3-week-old C3H/HeSlc mice. At 3 days and 1, 2, 4, 6, and 8 weeks post-attachment of the appliance, the mice were sacrificed by perfusion fixation. Frozen sagittal cryostat sections of the decalcified maxillary incisors were processed for immunohistochemistry of protein gene product 9.5, followed by histochemical determination of tartrate-resistant acid phosphatase activity to reveal sites of alveolar bone resorption. Despite the absence of bone resorption within the lingual PDL of control mice, distinct resorption sites were seen in the respective regions of the experimental animals. Unlike the controls, many Ruffini endings showing vague and swollen contours, with unusually long and pedunculated micro-projections were observed in the affected lingual PDL of the incisors in the experimental animals with short-term anterior crossbite induction. Club-shaped nerve terminations with few, if any, micro-projections were observed in the lingual PDL of experimental animals with long-term induction, as well as in aged control mouse incisors. Differences in the distribution of Ruffini endings were also observed. These results indicate that changing the direction of the force applied to the PDL results in rapid and prolonged changes in the morphology of Ruffini-like mechanoreceptors.

Abortive synaptogenesis as a factor in the inner hair cell degeneration in the Bronx Waltzer (bv) mutant mouse

The Bronx Waltzer (vb) mutation in the mouse results in the degeneration of most but not all of the primary auditory receptors, the inner hair cells, and their afferent neurons. We analyzed the ultrastructure of 94 inner hair cells in the intact postnatal mutant mouse and in neonatal cochleas in culture to understand the pathogenesis of hair cell death and to detect factors that may prevent it. The vb spiral neurons of the Bronx Waltzer display two distinctive features: some of them continue to divide mitotically for at least seven postnatal days, and the type I radial fibers that innervate inner hair cells display a deficiency in immunoexpression of GAD. The growing endings of spiral neurons converge around the inner hair cells or, in their absence, invade the outer hair cell region. Their profuse sprouting among inner spiral sulcus cells contributes to the characteristic ultrastructural picture of the bv cochlea. During the first three days after birth, 40% of the inner hair cells appear normal and innervated, 40% are mostly denervated and degenerating, and 20% are immature, with minimal or no neuronal appositions. However, in mutants 6 days and older only a few inner hair cells survive, and these show either normal or superfluous afferent innervation and axosomatic GABAergic efferent innervation. Degeneration of inner hair cells begins with a distention of the nuclear envelope and the ribosomal endoplasmic reticulum. The outer nuclear membrane eventually breaks, and exudate fills the cell interior. The cellular edema leads to cell death. We propose that success or failure in synaptic acquisition is a decisive factor in the survival or decline of the mutant inner hair cells. We also suggest that the developmental delay in maturation of the spiral ganglion neurons (type I) and the failure in their synaptogenesis may be caused by an impairment in neurotrophin (NT3/BDNF) synthesis by their mutant receptor cells.

Effects of columella removal on inner ear morphology in the chick

We are currently removing the single middle ear bone (columella) in the domestic chick to introduce chemical agents directly into the inner ear. Since we are interested in the effect of these agents on neural structures within the avian basilar papilla (BP), we are concerned about any subtle changes that might result from the surgical procedure of columella removal alone. The purpose of this study was to use light and transmission electron microscopy to analyze morphological changes in the inner ear after columella removal. Fifteen-day-old chicks underwent a unilateral, bilateral or a sham removal of the columella. After columella removal, the oval window was either plugged with Gelfoam or Kimwipe (standard accepted procedure to prevent possible perilymph leak) or left uncovered. After a 5-day survival period, morphological changes were observed in the tegmentum vasculosum (TV) of all ears receiving a columella removal as compared to unoperated ears. Further, ears with Gelfoam plugging the oval window also had damage to the hair cells and support cells of the basilar papilla. In contrast, there were no observable differences in either auditory afferent or efferent nerve terminals on hair cells in the BP from any ears that had the columella removed compared to those from unoperated ears. These results suggest that columella removal alone may produce morphological changes to the TV within 5 days of surgery but not to structures within the BP. On the other hand, columella removal with a Gelfoam plug results in damage not only to the TV but also to cells within the basilar papilla during this same survival time. Despite damage to other structures within the inner ear, cochlear efferent and afferent terminals on surviving hair cells were unaffected by columella removal with or without plugging.

A comparison of the innervation characteristics of the lateral spinal ligaments between normal subjects and patients with adolescent idiopathic scoliosis

Evidence is rapidly accumulating to suggest that general proprioceptive dysfunction might be a major contributing factor in the development of adolescent idiopathic scoliosis (AIS). The innervation of appropriate ligaments which has been shown to be involved in proprioceptive feedback mechanisms, has also been suggested to play a part in this sensory dysfunction. Accordingly, this study compared the innervation characteristics of lateral spinal ligaments from patients with AIS to similar measurements from control subjects. Using an antibody to neurofilament protein, Ruffini corpuscles, small and large nerve bundles, and free nerve endings were identified and their numbers and distribution patterns compared. In the control group, the innervation was found to be symmetrical between left and right sides but was more concentrated in the ventral portion of each ligament. No apparent morphological defect of the innervation was found in the lateral spinal ligaments of the scoliosis patients but the innervation densities of Ruffini corpuscles, single nerve fibres and total neural elements were significantly lower (p<0.01) than those found in normal subjects. These results suggest a possible mechanism for the production of AIS and warrant further study.

Morphological study of mechanoreceptors on the coracoacromial ligament

We performed gold chloride staining of coracoacromial ligaments removed at operation, observed the peripheral nerve endings in the ligament, and studied their distribution and changes with aging in order to clarify the proprioception of the shoulder joint. The coracoacromial ligament was found to contain four types of typical nerve endings: Pacinian corpuscles, Ruffini receptors, Golgi tendon organ-like receptors, and free nerve endings. In addition, non-typical Pacinian corpuscles and Ruffini receptors with non-typical morphology were present. There were also unclassifiable nerve endings with a morphology which did not fit any of the above categories. These typical, non-typical, and unclassifiable nerve endings were all widely distributed on the surface of the subacromial side at the insertion into the acromion and around the coracoid process in the ligament. Free nerve endings were found sporadically on the surface of the subacromial bursal side in the ligament. The resected coracoacromial ligaments (23 specimens) were divided into two groups based on the disorder that required surgery: a fracture group without subacromial impingement (5 specimens) and a group with subacromial impingement (18 specimens). Age-related changes in the number of nerve endings were compared in each group. The total number of nerve endings decreased with age in both groups. The number of Pacinian corpuscles, Ruffini receptors, Golgi tendon organ-like receptors, and free nerve endings of typical morphology tended to decrease with age. The data from the fracture and subacromial impingement groups were not analyzed statistically because of the difference in the number of specimens in each group. However, the total number of nerve endings was lower in the subacromial impingement group than in the fracture group at all ages. The typical nerve endings of the coracoacromial ligament in both groups tended to decrease in the elderly, suggesting that the proprioception of the shoulder joint may become impaired with aging.

The relationship between the degree of neurodegeneration of rat brain 5-HT nerve terminals and the dose and frequency of administration of MDMA ('ecstasy')

The effect of varying the dose and frequency of administration of 3,4-methylenedioxymethamphetamine (MDMA or 'ecstasy') on both the acute hyperthermic response and the long term neurodegeneration of 5-hydroxytryptamine (5-HT) nerve terminals in the brain has been studied in Dark Agouti rats. A single injection (4-15 mg/kg i.p.) of MDMA produced immediate dose-related hyperthermia and a dose-related decrease in 5-HT, 5-hydroxyindoleacetic acid (5-HIAA) and [3H]paroxetine binding in regions of the brain 7 days later, with a dose of 4 mg/kg having no degenerative effect. This dose was also without effect when given once daily for 4 days, but produced a marked loss of [3H]paroxetine binding and indole concentration ( approximately 55%) when given twice daily for 4 days. When a dose of 4 mg/kg was given twice weekly for 8 weeks it had no effect on these serotoninergic markers, despite a clear anorectic effect of the drug being seen. These data demonstrate that MDMA-induced neurodegeneration is related to both the dose and frequency of administration and indicate that damage to 5-HT neurones can occur in the absence of a hyperthermic response to the drug. We suggest that damage occurs when endogenous free radical scavenging mechanisms become overwhelmed or exhausted.

NGF delays rather than prevents the cholinergic terminal damage and delayed neuronal death in the hippocampus after ischemia

Cerebral ischemia induces damage of cholinergic terminals in the hippocampus, which preceded the delayed neuronal death (DND) of the CA1 pyramidal cells. We investigated the effects of nerve growth factor (NGF) on the cholinergic terminal damage after ischemia. Continuous NGF infusion (0.5 microg/7 days) into the lateral ventricle before and after 5 min ischemia prevented a decrease in choline acetyltransferase (ChAT)-immunoreactivity and disturbance of acetylcholine (ACh) release on the 4th day after ischemia, but not on day 7, i.e., NGF infusion caused delay in the progress of the cholinergic terminal damage. These findings show that the cholinergic terminal damage may result from deficiency of endogenous NGF in an ischemic brain. In addition, we investigated whether NGF would prevent the DND after ischemia. NGF infusion also caused delay in the progress of the DND until day 14. Our results suggested that the neuroprotective effect of NGF on the DND may be secondarily yielded by maintenance of communication between cholinergic terminal and the target CA1 cell, and that prevention of cholinergic terminal damage may be useful for the treatment of cerebrovascular disease.

Specific neurochemical derangements of brain projecting neurons in apolipoprotein E-deficient mice

Apolipoprotein E (apoE)-deficient mice provide a useful system for studying the role of apoE in neuronal maintenance and repair. Previous studies revealed specific memory impairments in these mice that are associated with presynaptic derangements in projecting forebrain cholinergic neurons. In the present study we examined whether dopaminergic, noradrenergic, and serotonergic projecting pathways of apoE-deficient mice are also affected and investigated the mechanisms that render them susceptible. The densities of nerve terminals of forebrain cholinergic projections were monitored histochemically by measurements of acetylcholinesterase activity, whereas those of the dopaminergic nigrostriatal pathway, the noradrenergic locus coeruleus cortical projection, and the raphe-cortical serotonergic tract were measured autoradiographically using radioligands that bind specifically to the respective presynaptic transporters of these neuronal tracts. The results obtained revealed that synaptic densities of cholinergic, noradrenergic, and serotonergic projections in specific brain regions of apoE-deficient mice are markedly lower than those of controls. Furthermore, the extent of presynaptic derangement within each of these tracts was found to be more pronounced the further away the nerve terminal is from its cell body. In contrast, the nerve terminal density of the dopaminergic neurons that project from the substantia nigra to the striatum was unaffected and was similar to that of the controls. The rank order of these presynaptic derangements at comparable distances from the respective cell bodies was found to be septohippocampal cholinergic > nucleus basalis cholinergic > locus coeruleus adrenergic > raphe serotonergic > nigrostriatal dopaminergic, which interestingly is similar to that observed in Alzheimer's disease. These results suggest that two complementary factors determine the susceptibility of brain projecting neurons to apoE deficiency: pathway-specific differences and the distance of the nerve terminals from their cell body.

Loss of nerve endings in the spinal dorsal horn after a peripheral nerve injury. An anatomical study in Macaca fascicularis monkeys

In patients, the long-term outcome of injuries to sensory nerves is poor. This is only partly due to mismatching of regenerating axons at the transection site. We found in the macaque monkey that 70% of the transganglionic labelling in the spinal dorsal horn was still significantly reduced 21 months after transection and suturing of the sensory radial nerve. The reduction was evenly distributed throughout the terminal field of nerve endings, which were labelled with a mixture of the intra-axonal nerve tracer wheat germ agglutinin-horseradish peroxidase conjugate and pure horseradish peroxidase.

Efferent targets of osseous CGRP-immunoreactive nerve fiber before and after bone destruction in adjuvant arthritic rat: an ultramorphological study on their terminal-target relations

We report the ultramorphological characterization of the terminal-target relation of sensory peptidergic nerve fibers in healthy and diseased osseous tissues. Bone tissue sections were immunoelectronmicroscopically investigated for calcitonin gene-related peptide (CGRP), a neuropeptide widely distributed in sensory peptidergic fibers. Ultramorphological relation of the osseous CGRP-immunoreactive (ir) nerve terminals and their target cells was comparatively analyzed using healthy, arthritic, and postarthritic bone specimens from control and adjuvant-induced arthritic rats. Terminal-like profiles of the osseous CGRP-ir axons were evidenced in direct contact with the metaphyseal osteoblasts and osteoclasts of the control animals. Terminal-like profiles were also noted in the vicinity of the periosteal lining cells. Nonterminal-like profiles did not make intimate spatial relation to the cells/structures surrounding the nerve. Osseous CGRP-ir terminals and axons, which are either uncovered or thinly ensheathed by the supportive tissues, were extensively degenerated in adjuvant-induced infiltration, whereas larger fibers were relatively resistant. Numerous CGRP-ir axons with distinctive features reinnervated the postarthritic, ossifying periosteum. CGRP-ir axons appeared to reinnervate the eroded surface of metaphyseal bone and cartilage as early as the recruited osteoblasts resume osteogenesis in the postarthritic metaphysis. The observed terminal-target relations in the healthy and diseased bone tissues give an ultramorphological basis for the putative trophic, modulatory actions of CGRP innervation of the bone cells.

Dopamine release and uptake rates both decrease in the partially denervated striatum in proportion to the loss of dopamine terminals

The present study tested the hypothesis that normal concentrations of extracellular dopamine are preserved in the partially denervated striatum without active compensatory changes in dopamine uptake or release. One to four weeks after adult rats were unilaterally lesioned with 6-hydroxydopamine, fast-scan cyclic voltammetry at Nafion-coated, carbon-fiber microelectrodes was used to monitor extracellular dopamine levels in vivo, under urethane anesthesia. Simultaneous voltammetric recordings were collected in the lesioned and contralateral control striata. Extracellular dopamine was elicited by bilateral electrical stimulation of the medial forebrain bundle. A 20 Hz stimulation evoked similar concentrations of extracellular dopamine in both lesioned and control striata, although tissue dopamine was decreased 30-70% in lesioned striata, as determined subsequently by HPLC-EC. However, kinetic analysis of the voltammetric recordings revealed that the concentration of dopamine released per stimulus pulse and Vmax for dopamine uptake decreased in proportion to the magnitude of the lesion. These data support the hypothesis that normal extracellular dopamine levels can be generated in the partially lesioned striatum in the absence of active neuronal compensation. These results also suggest that passive mechanisms involved in the regulation of extracellular dopamine play an important role in maintaining function during the preclinical or presymptomatic phase of Parkinson's disease.

Degeneration of intrapancreatic nerve fibers after chronic alcohol administration in mice

CONCLUSION

These results provide morphological evidence for an alcohol-induced selective intrapancreatic nerve degeneration. This affected mainly the nerve fibers that are inhibitory of the exocrine pancreas, and might represent the morphological background of hypersecretory state of the pancreas in chronic alcoholism.

METHODS

Intrapancreatic intrinsic nerves were studied by immunohistochemistry and electron microscopy after 4 mo of alcohol consumption and compared with control mice.

RESULTS

A dense network of nerve fibers was observed in the normal mouse pancreas around the blood vessels and ending on the exocrine cells. The presence of VIP, NPY, PP, SP, and serotonin in these nerves was demonstrated by immunohistochemistry. Four months of alcohol consumption did not result in apparent morphological changes of the pancreas. However, the majority of periacinar nerve terminals showed degenerative changes. Synaptic vesicles were diminished in number in some other nerve processes, whereas the perivascular nerve fibers were relatively well preserved. A slight decrease was found in the intensity of VIP and SP immunoreactivity, and the PP fibers almost disappeared.