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PubMed1996

Presynaptic 5-HT auto- and heteroreceptors in the human central and peripheral nervous system.

In view of the potential pathophysiological and therapeutic implications, presynaptic 5-HT auto- and heteroreceptors have been identified and characterized in isolated human tissues and their functional role has been determined. Such investigations have been carried out in different laboratories including that of the authors. Basic evidence for the involvement of inhibitory 5-HT receptors in modulation of 5-HT release in the cerebral cortex was obtained in slices: exogenous 5-HT inhibited 5-HT release in a manner susceptible to blockade by methiothepin, which given alone facilitated 5-HT release, probably by preventing endogenous 5-HT from activating the inhibitory receptors. The latter receptors are located on the 5-HT nerve terminals themselves, since 5-HT (and sumatriptan) also inhibited 5-HT release from cortical synaptosomes. Their pharmacological properties conform to those of the 5-HT1D class. Subclassification (5-HT1D alpha or 5-HT1D beta) has been tried with ketanserin which has an at least 60 times higher affinity for 5-HT1D alpha (pki = 7.1) than 5-HT1D beta receptors. Since ketanserin (0.32 microM) did not affect the concentration-response curve for 5-carboxamidotryptamine (5-CT), the presynaptic 5-HT autoreceptor may belong to the 5-HT1D beta rather than the 5-HT1D alpha subtype. The sympathetic nerve terminals of the human saphenous vein are endowed with inhibitory 5-HT1D beta heteroreceptors, as indicated by the potency ratio of several 5-HT receptor agonists in inhibiting noradrenaline release in strips of this blood vessels and by the ability of methiothepin, but not of ketanserin 0.3 microM, to act as an antagonist. Noradrenergic nerves in the dura mater, which probably innervate its microvasculature, may also be endowed with inhibitory 5-HT receptors, since 5-HT inhibited noradrenaline release from this tissue. In strips of atrial appendages, 5-HT receptor agonists (e.g. 5-HT, 5-CT and sumatriptan) inhibited noradrenaline release at potencies which are correlated with their ki values at 5-HT1D alpha and 5-HT1D beta receptors. Since this inhibitory effect was antagonized by ketanserin (0.3 but not 0.03 microM) and methiothepin, the presynaptic 5-HT receptor in this tissue may belong to the 5-HT1D alpha subtype. However, this conclusion needs further confirmation by experiments with more potent and subtype-selective antagonists of 5-HT1D alpha and 5-HT1D beta receptors.

Central Nervous System↗
PubMed2005

Role of kynurenines in the central and peripheral nervous systems.

Kynurenine (KYN) is an intermediate in the pathway of the metabolism of tryptophan to nicotinic acid. KYN is formed in the mammalian brain (40%) and is taken up from the periphery (60%), indicating that it can be transported across the blood-brain barrier (BBB). In the brain, KYN can be converted to two other components of the pathway: the neurotoxic quinolinic acid (QUIN) and the neuroprotective kynurenic acid (KYNA). QUIN is probably the most widely studied metabolite of KYN, because it may cause excitotoxic neuronal cell loss and convulsions by interacting with the N-methyl-D-aspartate (NMDA) receptor complex, a type of glutamate receptor. KYNA is another metabolite of KYN; its synthesis is catalysed by KYN aminotransferases. This is the only known endogenous NMDA receptor inhibitor, which can act at the glycine site on the receptor complex. Furthermore, KYNA non-competitively inhibits alpha7 nicotinic acetylcholine presynaptic receptors (nAChRs), inhibiting glutamate release, and regulates the expression of alpha4beta2 nAChR. It is well-known that the activation of excitatory amino acid (EAA) receptors can play a role in a number of neurodegenerative disorders, such as Parkinson's disease, Alzheimer's disease, stroke and epilepsy. Various studies have been made of whether the EAA receptor antagonist KYNA can exert a therapeutic effect in these neurological disorders. It has been established that KYNA has only a very limited ability to cross the BBB. Other KYNA derivatives have been synthesised (e.g. glucosamine-KYNA, 4-chloro-KYNA and 7-chloro-KYNA), which are well transported across the BBB and act on the glutamate receptors. Moreover, it has been demonstrated that probenecid, a known inhibitor of the transport of organic acids (e.g. KYNA), increases the cerebral concentration of KYNA. There is another new perspective to the maintenance of a high level of KYNA in the brain: the use of enzyme inhibitors, which can block the synthesis of the neurotoxic QUIN. These are some of the most promising possibilities as novel therapeutic strategies for the treatment of neurodegenerative diseases, in which the hyperactivation of amino acid receptors could be involved. The presence and importance of KYN derivatives in the periphery are also discussed in the light of recent publications.

Animals↗
PubMed2005

A 71-year-old male with 4 decades of symptoms referable to both central and peripheral nervous system.

May 2005. Combined demyelination of the central and peripheral nervous system is an uncommon disorder and has been referred to by many appellations. We present the case of a 71-year-old man with a progressive nervous system disorder beginning in his 30s. The diagnosis in life was unclear, but had over the years been variously considered to be Guillain-Barrè Syndrome (GBS), Friedreich ataxia, or multiple sclerosis (MS). At autopsy old CNS demyelination consistent with MS was found as well as chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) with onion bulb formation in hypertrophic nerves. Microscopic examination showed some onion bulb formation in the CNS as well as in peripheral nerves. The nosology of these disorders is discussed and relevant animal models briefly reviewed.

Aged↗
PubMed2005

Peripheral nervous system injuries in sport and recreation: a systematic review.

Many sports are associated with a variety of peripheral nervous system (PNS) injuries specific to that sport. A systematic review of sport-specific PNS injuries has not been attempted previously, and will assist in the understanding of morbidities and mortality associated with particular sporting activities, either professional or amateur. A systematic review of the literature using PubMed (1965-2003) was performed examining all known sports and a range of possible PNS injuries attributable to that sport. Numerous sporting activities (53) were found to have associated PNS injuries. The sports most commonly reported with injuries were football, hockey, soccer, baseball and winter activities. There are a number of sporting activities with injuries unique to the individual sport. This review should be of assistance for the neurologist, neurosurgeon, orthopaedic surgeon, physiatrist, sports medicine doctor, athletic trainer and general physician in contact with athletes possessing neurological injuries.

Arm Injuries↗
PubMed1995

Familial amyloid polyneuropathy associated with transthyretin Gly42 mutation: a quantitative light and electron microscopic study of the peripheral nervous system.

We performed extensive quantitative analyses of the peripheral nervous system (PNS) of two siblings with familial amyloid polyneuropathy (FAP) caused by a transthyretin (TTR) Gly42 mutation. Pronounced amyloid deposition was found in the sympathetic ganglia (SyG), dorsal root ganglia (DRG) and throughout the length of the peripheral nerve fibers with some accumulation in the more proximal portion. There was severe neuronal loss in the SyG and DRG together with nerve fiber depletion in the nerve trunk, while only a small amount of amyloid deposition with mild fiber loss was seen in the spinal roots. Sprouts of regenerating axons were very scanty even in the spinal nerves or roots. A teased fiber study mainly showed demyelinating fibers, but axonal degeneration was also present throughout peripheral nerves. An electron microscopic study showed fine amyloid fibrils in direct contact with the axoplasmic membrane of demyelinated axons and destruction of axons in some areas. Amyloid deposition within the PINS in this type of FAP resembled that in type I FAP (TTR Met30). However, direct axonal damage by amyloid fibrils appeared to be more prominent in our cases than in type I FAP. Lectin histochemistry using Ulex europaeus agglutinin I demonstrated preferential depletion of small neurons in the DRG and their primary afferent fibers in the spinal dorsal horn. Primary axonal degeneration and ganglionopathy due to amyloid deposition appear to be the pathogenetic mechanisms for peripheral neuropathy in this type of FAP.

Adult↗
PubMed1982

Cellular and subcellular localization of protein I in the peripheral nervous system.

The cellular and subcellular distribution of protein I, a major brain phosphoprotein, has been studied in the peripheral nervous system. The levels of protein I in various peripheral nerves and innervated peripheral tissues were determined by radioimmunoassay and radioimmunolabeling of polyacrylamide gels. The results indicated tha protein I is present throughout the peripheral nervous system. Denervation studies of adrenal medulla and iris suggested that the protein I contained in peripheral tissues is localized to the neuronal elements innervating those tissues. Protein I was found to be enriched in neurotransmitter vesicle fractions of peripheral nervous tissue. Moreover, protein I appeared to be transported from cell bodies to axons terminals at least partly in association with neurotransmitter vesicles.

Adrenal Glands↗
PubMed1999

Factors contributing to preferential motor reinnervation in the primate peripheral nervous system.

Functional recovery after nerve lesions in the peripheral nervous system requires the accurate regeneration of axons to their original target end organs. This paper examines axonal regeneration of the primate median nerve lesioned at the wrist over nerve gap distances of up to 50 mm. Nerve gaps were bridged by either a sural nerve graft or a biodegradable collagen nerve guide tube, and recovery was followed for up to 1100 d. Nondestructive physiological methods were used to serially examine the number of regenerated motor units, and binomial statistics were used to compare the observed number of regenerated motor units with that expected if axonal regeneration of motor neurons were random. We found up to twice the number of motor units expected by random regeneration in direct suture and sural cable graft groups but not in nerve guide repairs of 20 or 50 mm. In all repaired nerves, aberrant motor axon collaterals were detected in digital sensory nerve territory. The results support the contention that the aberrant fibers represent collaterals of an alpha-motor axon, which also innervates muscle. Although the aberrant motor axon collaterals remained in digital sensory nerve territory for long periods, they remained relatively immature compared with their sibling collateral projecting to muscle, or sensory axons within the digital nerve. The number of such aberrant motor axon collaterals decreased over time in some repair groups, suggesting a selective pruning of the inappropriate collateral under certain conditions.

Action Potentials↗
PubMed2001

Induction of type 3 iodothyronine deiodinase by nerve injury in the rat peripheral nervous system.

Thyroid hormones are essential for the development and repair of the peripheral nervous system. The type 2 deiodinase, which is responsible for the activation of T(4) into T(3), is induced in injured sciatic nerve. To obtain information on the type 3 deiodinase (D3) responsible for the degradation of thyroid hormones, we looked for its expression (mRNA and activity) in the sciatic nerve after injury. D3 was undetectable in the intact sciatic nerve of adult rats, but was rapidly and highly increased in the distal and proximal segments after nerve lesion. After cryolesion, D3 up-regulation disappeared after 3 d in the proximal segment, whereas it was sustained for 10 d in the distal segment, then declined to reach basal levels after 28 d, when functional recovery was completed. After a transsection preventing the nerve regeneration, up-regulation of D3 persisted up to 28 d at high levels in the distal segment. D3 was expressed in peripheral connective sheaths and in the internal endoneural compartment. D3 mRNA was inducible by 12-O-tetradecanoylphorbol-13-acetate in cultured fibroblasts or Schwann cells. In conclusion, induction of D3 in the peripheral nervous system after injury may play an important role during the regeneration process by adjusting intracellular T(3) levels.

Animals↗
PubMed2006

[Effect of complex rehabilitation by physical factors (therapeutic mud, waves of millimeter range) on the indices of inflammation process and immune status in patients with traumas of peripheral nervous system].

82 patients with traumas of peripheral nervous trunks (middle, ulnar, radial, tibular and tibial nerves) were investigated, including 44 persons with neuroapraxia of those trunks and 38 with axonotmesis. It was established that the patients with traumas of peripheral nervous trunks showed the presence of inflammatory process and sensitization of the body which was exposed in the reaction of precipitation at C-reactive protein with the increase of the content of serum glycoides and total nonspecific immunuglobulin E in blood serum. The investigated patients showed also decrease in nonspecific resistance of organism and change in immune status. All the above-referred shifts were more expressed at axonotmesis of peripheral nervous trunks. Rehabilitation with the use of Kumisi therapeutic mud and electro magneto field of millimeter range resulted decrease of inflammation process and body sensitization in patients with traumas of peripheral nervous trunks almost to disappearance of inflammation process and body sensitization. Such rehabilitation increased nonspecific resistance, normalized the indices of immune reactivity. The above-referred positive shifts were comparatively well expressed at neuroapraxia of peripheral nervous trunks.

Adult↗
PubMed1983

[Pharmacological studies on oxatomide. (5). Effect on the central and peripheral nervous systems].

The effect of oxatomide, an antiallergic drug, on the central and peripheral nervous systems were investigated, and the following results were obtained: Oxatomide at oral doses of 30-100 mg/kg produced little or no effect on the spontaneous and cooperative movements in mice, hexobarbital-induced hypnosis in mice, body temperature in rats, and did not induce muscle relaxation, the analgesic effect, anticonvulsive effects and anti-physostigmine effect. Oxatomide at doses of 300 mg/kg or more produced sedation followed by an increase in the responses to stimuli in mice and rats. These behavioral changes diminished within 7-8 hours. Oxatomide (2 mg/kg, i.v.) changed the EEG to a slightly drowsy pattern in unanesthetized, unrestrained rabbits. Neither the EEG arousal responses evoked by auditory stimulation or electrical stimulation to the mesencephalic reticular formation, nor the limic afterdischarges induced by electrical stimulation to the hippocampus or amygdala were affected by oxatomide at any of the doses employed. Oxatomide had no effect on the spinal reflex in cats, conditioned behavior in rats or local anesthesia in guinea pigs. These results suggest that oxatomide shows little effect on the central and peripheral nervous systems at a dose sufficient to elicit the antiallergic actions.

Analgesics↗
PubMedDate not supplied

Mechanisms of toxic injury in the peripheral nervous system: neuropathologic considerations.

The anatomical distribution and organization of the peripheral nervous system as well as its frequent ability to reflect neurotoxic injury make it useful for the study of nerve fiber and ganglionic lesions. Contemporary neuropathologic techniques provide sections with excellent light-microscopic resolution for use in making such assessments. The histopathologist examining such peripheral nerve samples may see several patterns of neurotoxic injury. Most common are axonopathies, conditions in which axonal alterations are noted; these axonopathies often progress toward the Wallerian-like degeneration of affected fibers. These are usually more severe in distal regions of the neurite, and they affect both peripheral and central fibers. Examples of such distal axonopathies are organophosphorous ester-induced delayed neuropathy, hexacarbon neuropathy, and p-bromophenylacetylurea intoxication. These axonopathies may have varying pathologic features and sometimes have incompletely understood toxic mechanisms. In such neuropathies with fiber degeneration, peripheral nerve axons may regenerate, which can complicate pathologic interpretation of neurotoxicity. On occasion neurotoxins elicit more severe injury in proximal regions of the fiber (not included in this review). Axonal pathology is also a feature of the neuronopathies, toxic states in which the primary injuries are found in neuronal cell bodies. This is exemplified by pyridoxine neurotoxicity, where there is sublethal or lethal damage to larger cytons in the sensory ganglia, with failure of such neurons to maintain their axons. Lastly, one may encounter myelinopathies, conditions in which the toxic effect is on the myelin-forming cell or sheath. An example of this is tellurium intoxication, where demyelination noted in young animals is coincident with toxin-induced interference of cholesterol synthesis by Schwann cells. In this paper, the above-noted examples of toxic neuropathy are discussed, with emphasis on mechanistic and morphologic considerations.

Animals↗