Red nucleus interleukin-1β evokes tactile allodynia through activation of JAK/STAT3 and JNK signaling pathways

We previously reported that interleukin-1β (IL-1β) in the red nucleus (RN) is involved in pain modulation and exerts a facilitatory effect in the development of neuropathic pain. Here, we explored the actions of signaling pathways, including the Janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3), c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK), p38 mitogen-activated protein kinase (p38 MAPK) and nuclear factor-κB (NF-κB) pathways, on RN IL-1β-mediated pain modulation. After a single dose of recombinant rat IL-1β (rrIL-1β, 10 ng) injected into the RN in normal rats, a tactile allodynia was evoked in the contralateral but not ipsilateral hindpaw, commencing 75 min and peaking 120 min postinjection. Up-regulated protein levels of phospho-STAT3 (p-STAT3) and p-JNK were observed in the RN 120 min after rrIL-1β injection, the increases of p-STAT3 and p-JNK were blocked by anti-IL-1β antibody. However, the expression levels of p-ERK, p-p38 MAPK, and NF-κB in the RN were not affected by rrIL-1β injection. RN neurons and astrocytes contributed to IL-1β-evoked up-regulation of p-STAT3 and p-JNK. Further studies demonstrated that injection of the JAK2 antagonist AG490 or JNK antagonist SP600125 into the RN 30 min prior to the administration of rrIL-1β could completely prevent IL-1β-evoked tactile allodynia, while injection of the ERK antagonist PD98059, p38 MAPK antagonist SB203580, or NF-κB antagonist PDTC did not affect IL-1β-evoked tactile allodynia. In conclusion, our data provide additional evidence that RN IL-1β is involved in pain modulation, and that it exerts a facilitatory effect by activating the JAK/STAT3 and JNK signaling pathways.

Quantitative Susceptibility Mapping in Parkinson's Disease

BACKGROUND

Quantitative susceptibility mapping (QSM) and R2* relaxation rate mapping have demonstrated increased iron deposition in the substantia nigra of patients with idiopathic Parkinson's disease (PD). However, the findings in other subcortical deep gray matter nuclei are converse and the sensitivity of QSM and R2* for morphological changes and their relation to clinical measures of disease severity has so far been investigated only sparsely.

METHODS

The local ethics committee approved this study and all subjects gave written informed consent. 66 patients with idiopathic Parkinson's disease and 58 control subjects underwent quantitative MRI at 3T. Susceptibility and R2* maps were reconstructed from a spoiled multi-echo 3D gradient echo sequence. Mean susceptibilities and R2* rates were measured in subcortical deep gray matter nuclei and compared between patients with PD and controls as well as related to clinical variables.

RESULTS

Compared to control subjects, patients with PD had increased R2* values in the substantia nigra. QSM also showed higher susceptibilities in patients with PD in substantia nigra, in the nucleus ruber, thalamus, and globus pallidus. Magnetic susceptibility of several of these structures was correlated with the levodopa-equivalent daily dose (LEDD) and clinical markers of motor and non-motor disease severity (total MDS-UPDRS, MDS-UPDRS-I and II). Disease severity as assessed by the Hoehn & Yahr scale was correlated with magnetic susceptibility in the substantia nigra.

CONCLUSION

The established finding of higher R2* rates in the substantia nigra was extended by QSM showing superior sensitivity for PD-related tissue changes in nigrostriatal dopaminergic pathways. QSM additionally reflected the levodopa-dosage and disease severity. These results suggest a more widespread pathologic involvement and QSM as a novel means for its investigation, more sensitive than current MRI techniques.

Delayed treatment with chondroitinase ABC reverses chronic atrophy of rubrospinal neurons following spinal cord injury

Degradation of extracellular matrix chondroitin sulphate proteoglycans (CSPGs) using Chondroitinase ABC (ChABC) is a promising strategy for the treatment of spinal cord injury, with potent effects on promoting functional recovery and anatomical repair in spinal injured animals. We have previously demonstrated that ChABC treatment prevents atrophy of corticospinal projection neurons following spinal injury in adult YFP-H mice. Here, we investigate whether ChABC-mediated repair of the cell body extends to rubrospinal projection neurons (RSNs), whether neuroprotective effects can be sustained long-term and importantly, whether delayed treatment with ChABC can reverse chronic atrophy. Adult YFP-H mice underwent unilateral rubrospinal tract transection and were treated with ChABC or a control enzyme, delivered either acutely post-injury or after a one month delay. Eight weeks following injury and control treatment, RSNs in the injured red nucleus, identified by YFP label and NeuN immunoreactivity, showed severe atrophy, with ~40% loss of mean cell area compared to uninjured neurons in the contralateral red nucleus. Both acute and delayed treatment with ChABC promoted a significant rescue of injured RSNs, restoring cell area to ~80% and ~70%, respectively, of that in uninjured neurons. Thus, we demonstrate for the first time that CSPG degradation in the injured spinal cord not only promotes sustained rescue of cell atrophy when delivered acutely but can also reverse chronic atrophy in descending projection neurons. Thus, modulation of the extracellular matrix can mediate neuroprotective effects both early and late after spinal cord injury.

BYHWD rescues axotomized neurons and promotes functional recovery after spinal cord injury in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Buyang Huanwu Decoction (BYHWD), a Chinese prescription that has been used for hundreds of years to treat paralysis, has gained attention recently due to its significant neuroprotective properties.

AIM OF THE STUDY

This study was to investigate whether BYHWD treatment protected axotomized rubrospinal neurons (RN) following spinal cord injury (SCI) in rats.

MATERIALS AND METHODS

Adult rats received a right lateral funiculus transection at the level between C3 and C4, and were either treated with BYHWD or with distilled water (DW) via gastrogavage. Effects on RN viability and atrophy were determined by Nissl staining, axon regeneration was examined by biotinylated dextran amine (BDA) tracing techniques and functional recovery was studied by a test of forelimb usage during spontaneous vertical exploration.

RESULTS

RN cell number and mean somal size were 20% and 29% higher, respectively, in BYHWD-treated rats relative to DW-treated rats. There were a small number of BDA-labeled axons in the caudal of injury site in BYHWD-treated rats, whereas no caudal axonal regeneration was detected in DW-treated rats. BYHWD-treated rats used the injured forelimb more often than rats treated with DW.

CONCLUSIONS

These results indicate that administration of BYHWD following SCI protects injured neurons, promotes regeneration, and enhances functional recovery.

Neuroimmunophilin ligands improve functional recovery and increase axonal growth after spinal cord hemisection in rats

We have previously shown that FK506 accelerates the rate of nerve regeneration in the peripheral nervous system (PNS) and increases regeneration of central nervous system (CNS) axons into a peripheral nerve graft. In the present study, we examined whether FK506 and a nonimmunosuppressive derivative (FK1706) improve functional recovery and long distance regeneration following a hemisection lesion of spinal cord at T10/T11. Rats were given daily subcutaneous injections of either FK506 (2 mg/kg/day), FK1706 (2 mg/kg/day), an equivalent volume of saline or 30% DMSO as vehicle, respectively. Functional recovery was assessed using a modified Tarlov/Klinger scale, walking along progressively narrower wooden beams (7.7-1.7 cm widths), and analysis of footprints obtained during walking. Compared to both control groups, FK506 and FK1706-treated animals demonstrated significant functional recovery 4 days (beam walking), 2 weeks (footprints), and 4 weeks (Tarlov/Klinger scale). By 11 weeks, FK506-treated and FK1706-treated animals were able to walk, albeit poorly, along even the narrowest (1.7 cm) beam. At 11 weeks, the spinal cords were re-exposed and a small piece of gel foam-soaked Fluoro-Gold was placed on the injured side 2-cm caudal to the first injury. Five days later, the animals were perfused and tissues prepared for fluorescence microscopy. FK506-treated and FK1706-treated rats demonstrate a significantly greater number of retrogradely labeled neurons in the red nucleus. The results implicate a nonimmunosuppressant mechanism in FK506's action and suggest that FK506 or a nonimmunosuppressant derivative may be useful for treatment of spinal cord injuries.

Glutathione monoethyl ester improves functional recovery, enhances neuron survival, and stabilizes spinal cord blood flow after spinal cord injury in rats

Secondary damage after spinal cord (SC) injury remains without a clinically effective drug treatment. To explore the neuroprotective effects of cell-permeable reduced glutathione monoethyl ester (GSHE), rats subjected to SC contusion using the New York University impactor were randomly assigned to receive intraperitoneally GSHE (total dose of 12 mg/kg), methylprednisolone sodium succinate (total dose of 120 mg/kg), or saline solution as vehicle. Motor function, assessed using the Basso-Beattie-Bresnahan scale for 8 weeks, was significantly better in GSHE (11.2+/-0.6, mean+/-S.E.M., n=8, at 8 weeks) than methylprednisolone (9.3+/-0.6) and vehicle (9.4+/-0.7) groups. The number of neurons in the red nuclei labeled with FluoroRuby placed caudally to the injury site was significantly higher in GSHE (158+/-9.3 mean+/-S.E.M., n=4) compared with methylprednisolone (53+/-14.7) and vehicle (46+/-16.4) groups. Differences in the amount of spared SC tissue at the epicenter and neighboring areas were not significant among experimental groups. In a second series of experiments, using similar treatment groups (n=6), regional changes in microvascular SC blood flow were evaluated for 100 min by laser-Doppler flowmetry after clip compression injury. SC blood flow fell in vehicle-treated rats 20% below baseline and increased significantly with methylprednisolone approximately 12% above baseline; changes were not greater than 5% in rats given GSHE. In conclusion, GSHE given to rats early after moderate SC contusion/compression improves functional outcome and red nuclei neuron survival significantly better than methylprednisolone and vehicle, and stabilizes SC blood flow. These results support further investigation of reduced glutathione supplementation after acute SC injury for future clinical application.

Rubrospinal neurons fail to respond to brain-derived neurotrophic factor applied to the spinal cord injury site 2 months after cervical axotomy

Numerous experimental therapies to promote axonal regeneration have shown promise in animal models of acute spinal cord injury, but their effectiveness is often found to diminish with a delay in administration. We evaluated whether brain-derived neurotrophic factor (BDNF) application to the spinal cord injury site 2 months after cervical axotomy could promote a regenerative response in chronically axotomized rubrospinal neurons. BDNF was applied to the spinal cord in three different concentrations 2 months after cervical axotomy of the rubrospinal tract. The red nucleus was examined for reversal of neuronal atrophy, GAP43 and Talpha1 tubulin mRNA expression, and trkB receptor immunoreactivity. A peripheral nerve transplant paradigm was used to measure axonal regeneration into peripheral nerve transplants. Rubrospinal axons were anterogradely traced and trkB receptor immunohistochemistry performed on the injured spinal cord. We found that BDNF treatment did not reverse rubrospinal neuronal atrophy, nor promote GAP-43 and Talpha1 tubulin mRNA expression, nor promote axonal regeneration into peripheral nerve transplants. TrkB receptor immunohistochemistry demonstrated immunoreactivity on the neuronal cell bodies, but not on anterogradely labeled rubrospinal axons at the injury site. These findings suggest that the poor response of rubrospinal neurons to BDNF applied to the spinal cord injury site 2 months after cervical axotomy is not related to the dose of BDNF administered, but rather to the loss of trkB receptors on the injured axons over time. Such obstacles to axonal regeneration will be important to identify in the development of therapeutic strategies for chronically injured individuals.

Effects of rubral microinjections of muscimol and bicuculline in a genetic animal model of paroxysmal dystonia

Previous studies suggested that GABAergic dysfunctions within the red nucleus are involved in stress-inducible paroxysmal dystonia of the dt(sz) mutant hamster. In the present study, rubral microinjections of the GABAA receptor agonist muscimol exerted only moderate antidystonic effects and the antagonist bicuculline failed to show significant effects on the severity of dystonia. These data indicate that disturbed rubral GABAergic inhibition is not important for the manifestation of dystonia in the dt(sz) mutant.

[Features and mechanisms of realization the respiratory influences of the extrapyramydal system structures]

In the publication the modern condition of the problem of suprabulbar regulation of breathing is analysed. The review on structure, neurochemistry and anatomic connections of the red nucleus and substantia nigra with the medullary respiratory center is submitted. The data on the respiratory effects of GABA and apomorphine microinjected into the red nucleus and substantia nigra as well as effects of their electrostimulation after the blockade of GABA and dopamine receptors in the respiratory center are discussed. The conceptual scheme of the mechanisms of realization the respiratory influences of the extrapyramydal system is offered.

The proximity of the lesion to cell bodies determines the free radical risk induced in rat rubrospinal neurons subjected to axonal injury

To find out whether close axonal injury resulted in greater free radical risk to cord-projection central neurons than distant ones, we studied the expressions of nitric oxide synthase, calcineurin, and superoxide dismutase in rat rubrospinal neurons following brainstem, C2 and T10 axotomies using immunohistochemical methods. We found that nitric oxide synthase expression was upregulated more following brainstem than C2 lesion while T10 lesion triggered no detectable changes. This response peaked at 1 week and returned to control level by 8-week-post-injury. At the same time, calcineurin, which activated nitric oxide synthase, was increased 1 week following brainstem and C2 axotomies. These suggest that close, but not distant, axotomy enhanced NO production, which appeared to be cytotoxic since blocking NO synthesis with N-nitro- l-arginine methyl ester reduced brainstem axotomy-induced rubrospinal cell loss. On the other hand, the mitochondrial Mn-superoxide dismutase, which competes with NO to prevent the formation of the cytotoxic free radical peroxynitrite, was notably reduced after brainstem but almost unaltered following C2 axotomy. Meanwhile, the cytosolic Cu/Zn-superoxide dismutase was not altered following C2 but increased after brainstem axotomy. Ultrastructurally, in rubrospinal neurons more mitochondria became swollen following brainstem than C2 axotomy. Based on these, we proposed that besides the NO-overproduction-induced toxicity, superoxide-loading-induced mitochondrial damage also added to hampering the survival of the closely axotomized neurons.

Alpha2- and beta-adrenoceptors differentially modulate GABAA- and GABAB-mediated inhibition of red nucleus neuronal firing

In mesencephalic red nucleus (RN), GABA-induced inhibition of neuronal firing is modulated by noradrenaline acting on alpha2- and beta-adrenoceptors. Since both GABAA and GABAB receptors are present in the rat RN, we have recorded the firing activity of RN neurons in vivo from anaesthetized rats to study how GABAA- and GABAB-mediated effects are modulated by either alpha2- or beta-adrenoceptor activation. Both the GABAA agonist isoguvacine and the GABAB agonist baclofen depressed the firing of RN neurons. During simultaneous application of clonidine, an alpha2-adrenoceptor agonist, half of the isoguvacine- and baclofen-mediated responses were modified: isoguvacine-mediated inhibition was enhanced by 97% without any change in effect duration, whereas baclofen responses were either increased or slightly reduced in the same number of cases. Application of isoprenaline, a beta-adrenoceptor agonist, increased isoguvacine effect in 66% of neurons without modifying effect duration; the amount of increase (43%) was significantly lower than that induced by clonidine. On the other hand, in the presence of isoprenaline, baclofen response was reduced in 72% of neurons with respect to both the amount (52%) and the duration (34%) of effect. Taken together, these results indicate that alpha2-adrenoceptors mainly enhance GABAA-induced inhibition and induce mixed effects on GABAB response; on the other side, beta-adrenoceptors exert an opposite modulation on GABA effects, respectively, enhancing and depressing GABAA- and GABAB-mediated responses.

Glial fibrillary acidic protein expression in the hamster red nucleus: effects of axotomy and testosterone treatment

Testosterone propionate (TP) administration coincident with facial nerve axotomy in the hamster attenuates glial fibrillary acidic protein (GFAP) expression in the facial nucleus that is normally increased following axotomy alone. This ability of TP to modulate astrocyte activity has been linked to the ability of steroid hormones to enhance the regenerative response of injured motor neurons. In an ongoing study designed to examine the potential influences of steroid hormones on centrally projecting motoneurons, the astrocyte reaction in the red nucleus was examined. In the present study, in situ hybridization was used to assess changes in GFAP mRNA in the hamster red nucleus following spinal cord injury (SCI) and TP treatment. Castrated male hamsters were subjected to right rubrospinal tract (RST) transection at spinal cord level T1, with half the animals implanted subcutaneously with Silastic capsules containing 100% crystalline TP and the remainder sham implanted. The uninjured red nucleus served as an internal control. Postoperative survival times were 1, 2, 7, and 14 days. Qualitative-quantitative analyses of emulsion autoradiograms were accomplished. Axotomy alone resulted in a significant but transient increase in GFAP mRNA levels at 2 days postoperative in the injured red nucleus compared with the contralateral uninjured red nucleus. However, in TP-treated animals, GFAP mRNA levels were no different than control levels at 2 dpo but were significantly increased at 7 dpo relative to contralateral control. Additionally, the increase in GFAP mRNA levels following TP treatment was significantly smaller than following axotomy alone. These data suggest that testosterone both delays and reduces the astrocytic reaction in the red nucleus following rubrospinal tract axotomy, and confirms a difference between peripheral and central glial responses to axotomy and steroid administration.

Histamine elicits neuronal excitatory response of red nucleus in the rat via H2 receptors in vitro

Perfusing slices with histamine (1-100 microM) produced an excitatory response in rat rubral neurons (118/132, 89.4%). The histamine-induced excitation was not blocked by the low-Ca2+/high-Mg2+ medium (n=10), supporting a direct postsynaptic action of the amine. Histamine H2 receptor antagonist ranitidine effectively blocked the excitatory response of rubral neurons to histamine (n=26), but H1 receptor antagonist triprolidine did not (n=24). The excitatory effect of histamine could be mimicked by dimaprit, a highly selective H2 receptor agonist (n=24), and the dimaprit-elicited excitation of the rubral neurons could be blocked by ranitidine (n=16), but not by triprolidine (n=9). In addition, H1 receptor agonist 2-pyridylethylamine could not elicit any response in rubral neurons (n=12). These results indicate that histamine excites red nucleus neurons through H2 receptors and suggest that the histaminergic afferent fibers may play an important functional role in the sensorimotor integration through the red nucleus.

Facilitation of the jaw reflexes by stimulation of the red nucleus in the rat

The effects of the red nucleus (RN) stimulation on the jaw-opening reflex (JOR) and the masseteric monosynaptic reflex (MMR) were studied in anesthetized rats. The JOR was evoked by electrical stimulation of the inferior alveolar nerve. The MMR was evoked by electrical stimulation of the mesencephalic trigeminal nucleus. The JOR and the MMR were recorded as electromyographic responses of the anterior belly of the digastric and the masseter muscles, respectively. The conditioning electrical stimulation of the RN facilitated both the JOR and the MMR bilaterally. The facilitatory effect on the JOR was much larger than that on the MMR. Additionally, microinjection of monosodium glutamate into the RN also elicited facilitation of the JOR and the MMR. The results suggest the RN plays an important role in reflex control of jaw movements.

Role of GABA A and GABA B receptors in GABA-induced inhibition of rat red nucleus neurons

We investigated GABA receptor subtypes mediating GABA-induced inhibition of red nucleus (RN) neuronal firing recorded extracellularly from anaesthetized rats. GABA response was mimicked by the GABA(A) agonists muscimol and isoguvacine in all cases and was partially blocked by the GABA(A) antagonist bicuculline. The GABA(B) agonist baclofen induced a long-lasting inhibition in 84% of cells. Neurons responding to either GABA(A) or GABA(B) agonists were equally distributed within the RN. The GABA(C) receptor agonist cis-amino-crotonic acid (CACA) did not modify RN neuronal firing; at high doses CACA occasionally induced inhibition abolished by bicuculline and thus mediated by GABA(A) receptors. We conclude that the inhibitory effects of GABA in the RN are mediated by both GABA(A) and GABA(B) receptors, whereas GABA(C) receptors are not involved.

Cessation of activity in red nucleus neurons during stimulation of the medial medulla in decerebrate rats

The pontine oral reticular nucleus, gigantocellular reticular nucleus (Gi) and dorsal paragigantocellular nucleus (DPGi) of the medulla are key elements of a brainstem-reticulospinal inhibitory system that participates in rapid eye movement (REM) sleep atonia. Our recent study has shown that excitation of these brainstem nuclei in decerebrate rats inhibits locus coeruleus cells and the midbrain locomotor region neurons related to muscle tone facilitation. In the present study we have examined the influences of electrical and chemical stimulation of Gi and DPGi inhibitory sites on the activity of neurons located in the magnocellular part of the red nucleus (RMC), a cell group that participates in both the tonic and phasic regulation of motor output. A total of 192 RMC neurons were recorded in precollicular-premammillary decerebrate rats with muscle rigidity and induced locomotion. Thirty-three RMC neurons were identified antidromically as rubrospinal (RMC-spinal) cells by stimulation of the contralateral dorsolateral funiculus at the L2 level. A total of 141 RMC neurons (88.7 %) and all RMC-spinal neurons were inhibited during electrical stimulation of Gi and DPGi inhibitory sites. This cessation of activity was correlated with bilateral muscle atonia or blockage of locomotion. Six RMC cells (3.8 %) were excited (224 +/- 50 %, n = 6, minimum = 98, maximum = 410, P < 0.05) and 11 cells (7 %) gave no response to Gi and DPGi stimulation. Microinjections of kainic acid (100 microM, 0.2 microl) into Gi and DPGi inhibitory sites, previously identified by electrical stimulation, produced a short-latency (35 +/- 3.5 s, n = 11) decrease of rigid hindlimb muscle tone and inhibition of all tested RMC (n = 7) and RMC-spinal (n = 5) neurons. These results, combined with our recent published data, suggest that inhibition of motor function during activation of the brainstem inhibitory system is related to both the descending inhibition of spinal motoneurons and suppression of activity in supraspinal motor facilitatory systems. These two mechanisms acting synergistically may cause generalized motor inhibition during REM sleep and cataplexy.

Reorganization of descending motor tracts in the rat spinal cord

Following lesion of the central nervous system (CNS), reinnervation of denervated areas may occur via two distinct processes: regeneration of the lesioned fibres or/and sprouting from adjacent intact fibres into the deafferented zone. Both regeneration and axonal sprouting are very limited in the fully mature CNS of higher vertebrates, but can be enhanced by neutralizing the neurite outgrowth inhibitory protein Nogo-A. This study takes advantage of the distinct spinal projection pattern of two descending tracts, the corticospinal tract (CST) and the rubrospinal tract (RST), to investigate if re-innervation of denervated targets can occur by sprouting of anatomically separate, undamaged tracts in the adult rat spinal cord. The CST was transected bilaterally at its entry into the pyramidal decussation. Anatomical studies of the RST in IN-1 antibody-treated rats showed a reorganization of the RST projection pattern after neutralization of the myelin associated neurite growth inhibitor Nogo-A. The terminal arborizations of the rubrospinal fibres, which are normally restricted to the intermediate layers of the spinal cord, invaded the ventral horn but not the dorsal horn of the cervical spinal cord. Moreover, new close appositions were observed, in the ventral horn, onto motoneurons normally receiving CST projections. Red nucleus microstimulation experiments confirmed the reorganization of the RST system. These observations indicate that mature descending motor tracts are capable of significant intraspinal reorganization following lesion and suggests the expression of cues guiding and/or stabilizing newly formed sprouts in the adult, denervated spinal cord.

Combination of gonadal steroid treatment and peripheral nerve grafting results in a peripheral motoneuron-like pattern of beta II-tubulin mRNA expression in axotomized hamster rubrospinal motoneurons

Rubrospinal motoneurons (RSMN) represent a population of androgen receptor-containing central motoneurons in rodents. In this study, the ability of testosterone propionate (TP), alone or in conjunction with a peripheral nerve graft (PNG), to alter the molecular program of injured RSMN was accomplished using betaII-tubulin cDNA probes and quantitative in situ hybridization (ISH). Initial fluoro-gold labeling experiments following a T1 hemisection established that, as in the rat, the hamster rubrospinal system is essentially crossed and that injured RSMN concentrate in the ventrolateral region of the red nucleus. In the second experimental series, adult gonadectomized male hamsters were subjected to a right T1 hemisection, with half of the operated animals immediately subcutaneously implanted with 1 10 mm TP Silastic capsule and the other half sham implanted. In a third experimental series, animals were subjected to T1 hemisection, followed by transplantation of a predegenerated autologous segment of peripheral nerve. Half of the animals in each group received TP implants at the time of spinal cord injury and PNG. Postoperative times were 2, 7, and 14 days (dpo). Quantitative ISH was performed using a betaII-tubulin-specific (33)P-labeled cDNA probe, emulsion autoradiography, and computerized image analysis for grain counting. Injury alone resulted in a short-lived increase in betaII-tubulin mRNA expression in the RSMN at 2 dpo, with a significant decline to well below control values at 7 and 14 dpo. TP treatment or PNG alone attenuated, but did not prevent, the down-regulation of betaII-tubulin mRNA. In contrast, the combination of TP with a PNG sustained the injury-induced increase in betaII-tubulin mRNA levels throughout the postoperative period of 2, 7, and 14 dpo. The synergistic effects of the two treatment strategies confirm the importance of targeting multiple aspects of the injury response for therapeutic intervention.

Fluoxetine-induced tremor: clinical features in 21 patients

We report a cohort of 21 patients (12 females and nine males), with a mean age of 42.4 years, who developed tremor after receiving fluoxetine at a mean dose of 25.7 mg per day. The mean latency period for tremor appearance was 54.3 days. Severity was found to be mild. In all patients, tremor was postural, with P<0.0005, compared to patients with rest tremor and P<0.05 compared to action/intention-tremor patients. The frequency range was 6-12 Hz/s. After fluoxetine was discontinued, tremor disappeared in 10 patients after a mean latency period of 35.5 days. In the remaining 11 patients, tremor persisted up to the end of the observation period (a mean of 449 days). We believe that this tremor phenomenon is due to the involvement of the red nucleus and the inferior olivary nucleus through their projections to the thalamus and the spinal cord.

Cerebellar input to magnocellular neurons in the red nucleus of the mouse: synaptic analysis in horizontal brain slices incorporating cerebello-rubral pathways

We studied the synaptic input from the nucleus interpositus of the cerebellum to the magnocellular division of the red nucleus (RNm) in the mouse using combined electrophysiological and neuroanatomical methods. Whole-cell patch-clamp recordings were made from brain slices (125-150 microm) cut in a horizontal plane oriented to pass through both red nucleus and nucleus interpositus. Large cells that were visually selected and patched were injected with Lucifer Yellow and identified as RNm neurons. Using anterograde tracing from nucleus interpositus in vitro, we examined the course of interposito-rubral axons which are dispersed in the superior cerebellar peduncle. In vitro monosynaptic responses in RNm were elicited by an electrode array placed contralaterally in this pathway but near the midline. Mixed excitatory post-synaptic potentials (EPSPs)/inhibitory post-synaptic potentials (IPSPs) were observed in 48 RNm neurons. Excitatory components of the evoked potentials were studied after blocking inhibitory components with picrotoxin (100 microM) and strychnine (5 microM). All RNm neurons examined continued to show monosynaptic EPSPs after non-N-methyl-D-aspartate (NMDA) glutamate receptor components were blocked with 10 microM 6,7-dinitroquinoxaline-2,3-dione or 5 microM 2,3-dihydro-6-nitro-7-sulfamoyl-benzo(f)-quinoxaline (NBQX; n=12). The residual potentials were identified as NMDA receptor components since they (i) were blocked by the addition of the NMDA receptor antagonist, D,L-2-amino-5-phosphonovaleric acid (APV), (ii) were voltage-dependent, and (iii) were enhanced by Mg(2+) removal. Inhibitory components of the evoked potentials were studied after blocking excitatory components with NBQX and APV. Under these conditions, all RNm neurons studied continued to show IPSPs. Blockade of GABA(A) receptors reduced but did not eliminate the IPSPs. These were eliminated when GABA(A) receptor blockade was combined with strychnine to eliminate glycine components of the IPSPs. Thus, IPSPs evoked by midline stimulation of the superior cerebellar peduncle, while blocking alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) and NMDA receptors, raise the possibility of direct inhibitory inputs to RNm from the cerebellum. In summary we propose that the special properties of the NMDA receptor components are considered important for the generation of RNm motor commands: their slow time course will contribute a steady driving force for sustained discharge and their voltage dependency will facilitate abrupt transitions from a resting state of quiescence to an active state of intense motor command generation.

Function of the hypothalamo-pituitary-adrenocortical system during ontogenesis in rats with inherited stress-induced arterial hypertension

The functional activity of the hypothalamo-pituitary-adrenocortical system (HPAS) during the development of rats with inherited stress-induced arterial hypertension (HSIAH rats) was compared with that in normotensive Wistar rats. In rats aged 2, 3, 4, 6, 8, 10, 12, and 18 weeks, competitive protein binding assays were used to estimate peripheral blood plasma corticosterone levels at rest and after 1 h of restricted mobility in mesh cylinders. Basal corticosterone levels and HPAS responses to stress were lower during ontogenesis in hypertensive rats than in Wistar rats of the same age. The exception was rats aged four weeks, when HSIAH rats started to develop hypertension and their HPAS was more sensitive to emotional stress than was the case in Wistar rats, this being associated with the greater reaction of the adrenals to ACTH. Decreased reactions of the HPAS to emotional stress in adult HSIAH rats is not associated with loss of adrenal ACTH sensitivity.

The role of the ventrolateral nucleus of the thalamus in the switching of descending influences to motor activity in the rat

Studies on rats showed that the facilitating influence of preliminary transection of the rubrospinal tract on recovery of motor activity and operant reflexes disrupted by lesioning of the red nucleus was more apparent when lesioning was chemical than when lesioning was electrolytic. This is due to the survival of cerebellothalamic fibers to the ventrolateral nucleus of the thalamus after chemical lesioning of the red nucleus with quinolinic acid. It was also shown that preliminary lesioning of the ventrolateral thalamic nucleus strongly hindered the switching of motor activity under the control of the corticospinal tract in rats subjected to section of the rubrospinal tract and lesioning of the red nucleus.

Serotonin modifies the neuronal inhibitory responses to gamma-aminobutyric acid in the red nucleus: a microiontophoretic study in the rat

The effects of 5-hydroxytryptamine (5-HT) on the inhibitory responses evoked by gamma-aminobutyric acid (GABA) in neurons of the red nucleus (RN) were studied using a microiontophoretic technique. Extracellular unitary recordings performed in anesthetized rats demonstrated that 5-HT ejection influenced GABA-evoked inhibition in 94% of RN neurons, enhancing them in 52% and depressing them in 46% of cases. Both effects were specific and dose-dependent,although enhancements or depressions of the GABA responses were respectively inversely and directly related to the doses of 5-HT applied. The type of modulation exerted by 5-HT on the GABA responses was independent of the action of the amine on background firing. In fact, 5-HT induced an enhancement of the GABA responses in neurons mostly located in the rostral RN and a depression in those in the caudal RN. The application of 8-hydroxy-2(di-n-propylamino)tetralin, a specific 5-HT(1A) receptor agonist, enhanced GABA responses, whereas alpha-methyl-5-hydroxytryptamine, a 5-HT(2A) receptor agonist, depressed them. Both the 5-HT(2) antagonist methysergide and the 5-HT(2A) selective antagonist ketanserin were able to block partially or totally the depressive action of 5-HT on GABA responses. In contrast, the same 5-HT antagonists mimicked the enhancing action of 5-HT on the GABA responses or were ineffective. Application of bicuculline, a GABA(A) receptor antagonist, enhanced the excitatory action of 5-HT on the background firing and slightly reduced the inhibitory action. It is concluded that 5-HT is able to modulate GABA-evoked responses in RN neurons by acting on both 5-HT(1A) and 5-HT(2A) receptors. The functional significance of a serotonergic control on GABAergic inhibitory effects in RN is discussed.

Pharmacological identification of SM-21, the novel sigma(2) antagonist

SM-21 is a tropane analogue with high affinity and selectivity for sigma(2) receptor subtype. In the absence of highly selective sigma(2) antagonists, the aim of the present study was to determine whether SM-21 is endowed with antagonistic activity. The experiments were conducted in rats by inducing neck dystonia, which is reported to be subsequent to activation of sigma(2) receptors. SM-21 (10 nmol/0.5 microl) was able to prevent torsion of the neck obtained by administration of the sigma(1)-sigma(2) agonist 1,3-di-(2-tolyl)guanidine (DTG, 5 nmol/0.5 microl) in the red nucleus. These data indicate that SM-21 is a potent and selective sigma(2) antagonist.

Biperiden hydrochlorate ameliorates dystonia of rats produced by microinjection of sigma ligands into the red nucleus

It has been reported that the imbalance of anticholinergic and antidopaminergic activity of each neuroleptic drug correlates with the capacity to produce neuroleptic-induced acute dystonia (NAD) and the major focus of NAD is thought to be the striatum. Anticholinergic drugs are highly effective on NAD, but they are partially effective on neuroleptic-induced tardive dystonia and their effect on idiopathic dystonia is disappointing. Recently, it has been reported that the unilateral microinjection of sigma (sigma) ligands into the red nucleus induces torticollis of rats. This animal model appears to be a model of dystonia, but it is not clear whether it is suitable for NAD in man. To clarify this issue, we investigated the effect of an anticholinergic drug, biperiden hydrochlorate (BH), on this animal model. This study revealed that BH dose-dependently ameliorated dystonia of rats induced by two sigma ligands, whether each sigma ligand had dopaminergic affinity or not. This animal model of dystonia appears to be a model of NAD in man from the viewpoint of treatment-response. The results also suggest that not only dopaminergic and cholinergic systems but also sigma system, and not only the striatum but also the red nucleus, may play an important role in the pathophysiology of NAD.

FK506 increases the regeneration of spinal cord axons in a predegenerated peripheral nerve autograft

The authors examined the ability of FK506 to accelerate axonal regeneration of rat spinal cord axons in a peripheral nerve (PN) graft. Predegenerated autografts were produced by transecting the left tibial nerve 1 week prior to spinal cord implantation into the lumbar (L-3-L-4) spinal cord. Rats were given daily injections of either FK506 (5 mg/kg, subcutaneous) or vehicle for 21 days. The PN grafts from FK506-treated rats contained larger sized regenerating axons compared with vehicle-treated controls, and mean axonal areas increased by 25% at 7.5 mm along the PN graft. Fluoro-Gold retrograde labeling confirmed that the regenerating axons originated from the central nervous system. Unexpectedly, the majority (>50%) of neurons in the red nucleus were retrogradely labeled in the FK506-treated animals only. The results indicate that FK506 not only accelerates the elongation of spinal cord axons but also promotes regeneration of rubrospinal neurons.

Neurotransmitter-mediated control of neuronal firing in the red nucleus of the rat: reciprocal modulation between noradrenaline and GABA

The electrical activity of neurons from the red nucleus, a mesencephalic structure involved in motor control, is under the influence of several neurotransmitters released from afferent fibers and/or from local interneurons. We have investigated the combined effects of gamma-aminobutyric acid (GABA) and noradrenaline (NA), both present at high levels in the red nucleus, on the firing activity of single rubral neurons recorded extracellularly in vivo on anesthetized adult rats. NA inhibited the firing activity of a large part of rubral neurons and induced excitatory or biphasic inhibitory/excitatory effects in a smaller group of cells. Neuronal firing was also inhibited by GABA in all the cells studied. When the effect of GABA was tested during continuous applications of NA, the magnitude of GABA response was modified in 58% of the cells: the effect of GABA was potentiated by NA in half of the responding neurons and was decreased in the remaining half. NA-induced potentiation of GABA response was mimicked by the alpha(2)-adrenoceptor agonist clonidine and was abolished by the alpha(2)-adrenoceptor antagonist yohimbine. On the other side, the decrease of GABA response was reproduced by the beta-adrenoceptor agonist isoprenaline and was blocked by timolol, an antagonist of beta-adrenoceptors. Neuronal firing activity was reduced by nipecotic acid, an inhibitor of GABA reuptake mechanism, and was instead increased during application of the GABA(A) receptor antagonist bicuculline, suggesting that rubral neurons in vivo were under tonic control by endogenous GABA. Both the inhibitory and the excitatory effects of NA were reduced in the presence of nipecotic acid and were instead potentiated during application of bicuculline, suggesting that NA responses were modified by endogenous GABA. Taken together, our results indicate a reciprocal modulation between the effects of GABA and NA on neuronal firing activity in the red nucleus of the rat: GABA depresses the responsiveness of rubral neurons to NA, whereas NA is able either to potentiate or to decrease the effects of GABA by activation of alpha(2)- and beta-adrenoceptors, respectively. The functional significance of such interaction, as well as the possible implication in diseases affecting motor control, will be discussed.

Neuroprotective and neurodestructive functions of nitric oxide after spinal cord hemisection

Nitric oxide (NO) may subserve different functions in different central neurons subjected to axotomy. The difference may depend on whether the neurons basally express neuronal nitric oxide synthase (nNOS), a biosynthetic enzyme of NO. This is supported by our previous finding that suggests the differential role of NO in neurons of nucleus dorsalis (ND) and red nucleus (RN) which have different basal expression of nNOS. This study aimed to establish firmly the functions of NO, as revealed by nNOS immunoreactivity and nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) histochemistry, by the administration of endogenous NO donor, l-arginine (l-arg), and NOS inhibitor, l-N(G)-nitroarginine methyl ester (l-NAME). To relate the role of NO to glutamate receptors (GluR), the distributions of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) and N-methyl-d-aspartate receptor (NMDAR) in the two nuclei were revealed by immunohistochemical techniques. nNOS immunoreactivity was void in ND neurons, but expressed weakly in the RN normally. It was induced in ipsilateral ND neurons and upregulated on both sides of RN after spinal cord hemisection. Neuronal loss in the ipsilateral ND was augmented by l-arg, but reduced by l-NAME. In the contralateral RN, l-arg attenuated neuronal loss. NMDAR1 was present in most neurons in ND. After axotomy, some NMDAR1 immunoreactive neurons of the ipsilateral ND were induced to express NOS, whereas RN neurons showed strong staining for NMDAR1 and all the AMPA subunits. Most of the NOS-positive neurons in the RN were coexistent with GluR2 in normal rats and those subjected to axotomy. The present data demonstrated that NO exerted neurodestructive function in the non-NOS-containing ND neurons characterized by NMDAR as the predominant glutamate receptor. NO might be beneficial to the NOS-containing RN neurons. This could be attributed to the presence of GluR2. Possible diverse synthesizing pathways of NO in two different central nuclei were suggested from the observation that NOS was colocalized with NADPH-d in ND neurons, but not in RN neurons.

Survival effects of BDNF and NT-3 on axotomized rubrospinal neurons depend on the temporal pattern of neurotrophin administration

This study shows that both BDNF and NT-3 can prevent cell death in axotomized adult rat rubrospinal neurons (RSNs), but that the efficacy of neuroprotection depends on the temporal pattern of treatment. At 8 weeks after cervical spinal cord injury, 51% of the RSNs had died. Subarachnoidal BDNF infusion into the cisterna magna for 4 weeks resulted in neuronal hypertrophy and 71% survival. Continuous infusion for 8 weeks into the lumbar subarachnoidal space with either BDNF or NT-3 gave similar survival rates, while a combination of BDNF and NT-3 resulted in 96% survival, although the cells were atrophic. When administration of either BDNF or NT-3 was delayed and performed during postoperative weeks 5-8, the number of surviving neurons was increased compared to early treatment. Delayed treatment with a combination of BDNF and NT-3 resulted in complete survival and a reduction in neuronal atrophy. A decreased expression of TrkB receptors and microtubule-associated protein-2 in the RSNs after axotomy was counteracted by BDNF and NT-3. Microglial activity remained increased even when complete cell survival was achieved. Thus, the combination of neurotrophins as well as the temporal pattern of treatment need to be adequately defined to optimize survival of injured spinal tract neurons.

Rescue of axotomized rubrospinal neurons by brain-derived neurotrophic factor (BDNF) in the developing opossum, Didelphis virginiana

Many rubrospinal neurons die in developing opossums when their axon is cut at thoracic levels of the spinal cord and in the present study we asked whether they can be rescued by brain-derived neurotrophic factor (BDNF). Bilateral injections of Fast Blue (FB) were made into the rostral lumbar cord to prelabel rubrospinal neurons and 5 days later the rubrospinal tract was cut unilaterally by hemisecting the thoracic cord. Immediately after hemisection, BDNF-soaked gelfoam was placed into the lesion cavity. Since pilot data indicated that one application of BDNF was not sufficient to produce a rescue effect, a second application was made 7 days later. Seven days after the second application the pups were killed by an overdose of anesthetic so that the red nucleus contralateral and ipsilateral to the lesion site could be examined for labeled neurons. The rubrospinal tract is almost entirely crossed, so the red nucleus contralateral to the lesion contained many axotomized neurons, whereas the red nucleus ipsilateral to it did not. Age-matched controls were subjected to the same procedures, but the gelfoam applied to the lesion site in the experimental animals was soaked only in the vehicle used to deliver BDNF. In all cases, labeled neurons were fewer in number in the red nucleus contralateral to the lesion than ipsilateral to it. It was of particular interest, however, that labeled neurons contralateral to the lesion were more numerous in the animals treated with BDNF than in the controls. We conclude that BDNF rescues at least some rubrospinal neurons from axotomy-induced cell death in developing opossums suggesting that loss of access to BDNF, and perhaps other neurotrophins, contributes to failure of rubrospinal neurons to survive axotomy.

Survival of chronically-injured neurons can be prolonged by treatment with neurotrophic factors

Axonal regeneration by chronically-injured supraspinal neurons can be enhanced by neurotrophic factor treatment at the site of injury, although the number of regenerating neurons decreases as the interval between spinal cord injury and treatment increases. This study investigated whether this decline in regenerative response could be due to continued loss of neurons during the post-injury period. Adult rats received a cervical hemisection lesion and axotomized neurons were labeled by retrograde transport of True Blue from the lesion site. Animals were killed one, four or eight weeks after injury and surviving neurons (True Blue-labeled) were counted in the red nucleus and lateral vestibular nucleus. The neuron number in the lateral vestibular nucleus was stable for eight weeks after spinal cord injury, while survival in the red nucleus decreased by 25% between four and eight weeks. To test how neurons respond to a second injury with or without trophic factor treatment, at four, eight, 14 or 22 weeks after injury the lesion cavity was enlarged by 0.5 mm in a rostral direction. Gel foam saturated with ciliary neurotrophic factor, brain-derived neurotrophic factor or basic fibroblast growth factor was placed into the cavity. Animals were killed four weeks later. Re-injury of the spinal cord caused a significant decrease in neuron survival in both the red nucleus and lateral vestibular nucleus, the effects of which were lessened by treatment with ciliary neurotrophic factor or brain-derived neurotrophic factor for the red nucleus and with ciliary neurotrophic factor for the lateral vestibular nucleus, when re-injured at four or eight weeks. Basic fibroblast growth factor did not affect neuron survival at any time post-injury. Ciliary neurotrophic factor was not effective with longer delays (14 or 22 weeks) between the initial injury and re-injury. These results indicate a delayed pattern of secondary neuronal cell loss after spinal cord injury that is exaggerated by re-injury, but which can be ameliorated by treatment with neurotrophic factors.

Relationship between modulation of the cerebellorubrospinal system in the in vitro turtle brain and changes in motor behavior in rats: effects of novel sigma ligands

Saturation and competition binding studies showed that the turtle brain contains sigma sites labeled by both [3H]di-o-tolylguanidine (DTG) and [3H](+)-pentazocine. There was a significant correlation between the IC50 values of sigma ligands for [3H]DTG sites in the turtle vs. rat brain, suggesting that the sites are comparable in the two species. In contrast, [3H](+)-pentazocine, which primarily labels sigma1 sites in the rodent brain, labels a heterogeneity of sites in the turtle brain. In extracellular recordings from the in vitro turtle brainstem, some sigma ligands enhanced the burst responses of red nucleus (RN) neurons (DTG, haloperidol, BD1031, BD1052, BD1069) while other sigma ligands decreased the burst responses (BD1047, BD1063). Control compounds (turtle Ringer vehicle control, opiate antagonist naloxone, atypical neuroleptic sulpiride) had no significant effects on the RN burst responses recorded from the in vitro turtle brain. The ED50s of the ligands for altering the burst responses in RN neurons from the turtle brain were correlated with their IC50s for turtle brain sites labeled with [3H]DTG, but not [3H](+)-pentazocine; this pattern is identical to that previously reported in rats, where there is a correlation between the potencies of sigma ligands for producing dystonic postures after microinjection into the rat RN and their binding to rat brain sites labeled with [3H]DTG, but not [3H](+)-pentazocine. When the novel sigma ligands were microinjected into the rat RN, dystonic postures were produced by ligands that increased the burst duration of RN neurons in the turtle brain. Novel sigma ligands that reduced the burst responses in the in vitro turtle brain have previously been reported to have no effects on their own when microinjected into the rat RN, but to block the dystonic postures produced by other sigma ligands. Taken together, the data suggest that the opposite effects of the novel ligands in the turtle electrophysiological studies represent the actions of agonists vs. antagonists, and that the directionality of the effects has predictive value for the expected motor effects of the drugs.

Pharmacological inactivation in the analysis of the central control of movement

In this review, we describe how pharmacological inactivation can be used to elucidate the central control of skilled limb movement. Local anesthetics and tetrodotoxin block neuronal cell bodies and passing fibers while gamma-aminobutyric acid (GABA) and muscimol only block cell bodies. Blockade induction time is short (several minutes) for all the agents. Blockade duration produced by local anesthetics and GABA is 15-60 min, while that of tetrodotoxin and muscimol is up to several days. We describe our drug injection system, with an integrated microelectrode and a viewing port for visually monitoring drug flow into the injection cannula. We used glucose metabolism to assess the extent of inactivation. Intracortical lidocaine or muscimol injection produces a central core of maximal hypometabolism (1 mm radius), which could be due to drug spread, surrounded by an extensive region (several millimeters) of reduced hypometabolism, possibly due to reduced synaptic activity of neurons receiving projections from the core region. Drug injection only depresses neuronal activity, which contrasts with cooling, where there can be neuronal hyperexcitability at the periphery of the inactivation site. Our experiments in behaving animals show how pharmacological inactivation is an effective analytical tool for dissecting the differential functional contributions of subcortical and cortical forelimb representations to limb movement control.

Heterogeneity of ventral tegmental area neurons: single-unit recording and iontophoresis in awake, unrestrained rats

Single-unit recording combined with iontophoresis of dopamine, GABA, and glutamate was used in awake, unrestrained rats to characterize the electrophysiological and receptor properties of neurons in the ventral tegmental area under naturally occurring behavioural conditions. All isolated ventral tegmental area units (n=90) were analysed and compared with cells (n=58) recorded from dorsally adjacent areas of the pre-rubral area and red nucleus. Two distinct neuronal groups were identified in the ventral tegmental area: units with triphasic, long-duration spikes (78/90) and units with biphasic, short-duration spikes (12/90). Although all long-spike units discharged in an irregular, bursting pattern with varying degrees of within-burst decrements in spike amplitude, they could be further subdivided into at least three distinct subgroups. Type I long-spike units (36/78) discharged at a relatively slow and stable rate (mean: 6.03 imp/s; range: 0.42-15.78) with no evident fluctuations during movement. These cells were inhibited by dopamine and GABA and responded to glutamate with a low-magnitude excitation accompanied by a pronounced decrement in spike amplitude and a powerful rebound inhibition. Type II long-spike units (23/78) had relatively high and unstable discharge rates (mean: 22.82 imp/s; range: 4.42-59.67) and showed movement-related phasic activations frequently followed by partial or complete cessation of firing. Some Type II cells (4/9) were inhibited by dopamine, but all were excited by glutamate at very low currents (0-10 nA). With an increase in current, the glutamate-induced excitation often (18/22) progressed into a cessation of firing. All these cells were inhibited by GABA followed by a strong rebound excitation (8/9), which also frequently (6/8) resulted in cessation of firing. Type III long-spike units (19/78) had properties that differed from either Type I or Type II cells, including a lack of spontaneous firing (5/19). Short-spike ventral tegmental area units were either silent (4/12) and unresponsive to dopamine and GABA or spontaneously active (range: 0.89-34.13 imp/s) and inhibited by GABA and, in some cases (2/8). by dopamine; all were phasically activated during movement and glutamate iontophoresis. It appears that ventral tegmental area neurons, including those with long-duration spikes, do not comprise a uniform population in awake, unrestrained rats. Type I, long-spike units match the characteristics of histochemically-identified dopamine neurons, and they appear to express dopamine autoreceptors, which may explain the relatively slow, stable rate of activity and the limited responsiveness to excitatory inputs. Although the nature of the other long-spike units in our sample is unclear, they may include dopamine neurons without autoreceptors as well as non-dopamine cells. The heterogeneity of ventral tegmental area neurons is an important consideration for further attempts to assess the role of the mesocorticolimbic dopamine system in motivated behaviour.

Activation of N-methyl-D-aspartate receptors in the feline retrorubral nucleus elicits orofacial dyskinesia

Stimulation of dopamine receptors within a circumscribed subregion of the feline caudate nucleus, that is the anterodorsal part of this nucleus, with dopamine or the dopamine receptor agonist (3,4-dihydroxyphenylimino)-2-imidazoline (DPI) elicits orofacial dyskinesia. Orofacial dyskinesia is a syndrome of tic-like contractions of the facial muscles which ends with a tongue protrusion. Afferent fibres of the anterodorsal part of the caudate nucleus are known to emanate from the retrorubral nucleus, including the dopaminergic A8 cell group. The present study was undertaken to investigate whether excitation of A8 cells can mediate and/or modulate orofacial dyskinesia. For this purpose, the activity of the retrorubral nucleus was manipulated with local injections of N-methyl-D-aspartate (NMDA). These local injections into the retrorubral nucleus were subsequently combined with manipulations of the dopamine transmission in the anterodorsal part of the caudate nucleus with local injections of DPI. The present study shows that injections of NMDA into the retrorubral nucleus elicits orofacial dyskinesia. This effect is dose-dependent, NMDA-specific, and inhibited by intra-caudate injections of DPI.

5-Hydroxytryptamine modifies neuronal responses to glutamate in the red nucleus of the rat

The effects of 5-hydroxytryptamine (5-HT) on the responses of red nucleus (RN) neurones to glutamate (glu) and its agonists were studied using a microiontophoretic technique in anaesthetised rats. Extracellular unitary recordings of RN neuronal activity showed that 5-HT application induced a significant and reversible depression of glu-evoked excitations in 85% of the RN units tested. This effect was independent of the action of the amine on background firing, which appeared enhanced in the majority of cases but was either depressed or uninfluenced in other cases. Microiontophoretic 5-HT also depressed the excitatory responses evoked in RN neurones by electrical stimulation of sensorimotor cortex. Methysergide application, which prevented the enhancing effects of 5-HT on the background firing, was scarcely effective in antagonising the depression of glu responses. In contrast, the serotonergic effects on the glu responses were reduced by the iontophoretically applied antagonist of 5-HT1A receptors, NAN-190. Microiontophoretic 5-HT was also able to influence the neuronal responses evoked by glu agonists quisqualate (quis) and N-methyl-D-aspartate (NMDA), acting on non-NMDA and NMDA receptors respectively. In fact 5-HT depressed quis-evoked excitations and induced mixed effects on NMDA responses, which were reduced in 45%, enhanced in 34% and unmodified in 21% of the units tested. These results suggest that 5-HT is able to modulate the motor glutamatergic input to RN by acting mostly on non-NMDA receptors. The modulation of non-NMDA and NMDA receptors by 5-HT in the RN appears significant and its functional meaning is discussed.

Expression of beta-calcitonin gene-related peptide in axotomized rubrospinal neurons and the effect of brain derived neurotrophic factor

The mRNA levels for alpha- and beta-calcitonin gene-related peptide (CGRP) in rat rubrospinal neurons were studied by in situ hybridization 3, 7, 14, 28 and 56 days following cervical spinal hemisection. CGRP-like immunoreactivity (LI) in the rubrospinal neurons and the rubrospinal tract in cervical spinal cords were examined using immunohistochemistry. There was almost no signal for alpha- and beta-CGRP mRNAs and undetectable level of CGRP-LI in the rubrospinal neurons ipsilateral to cervical spinal hemisection (control side). Fourteen days after spinal hemisection, the rubrospinal neurons contralateral to cervical hemisection (axotomized side) showed CGRP-LI in their cell bodies, and CGRP containing fibers were observed in the lateral funiculi just proximal, but not distal, to the injury sites. In situ hybridization showed upregulation of beta-CGRP mRNA in a subpopulation of the rubrospinal neurons on the axotomized side. The proportion of beta-CGRP mRNA-expressing neurons reached its maximum (approximately 19%) 4 days following axotomy and slowly decreased to about 5% 56 days after axotomy. The percentage of alpha-CGRP mRNA-expressing neurons was much lower than that of beta-CGRP mRNA (maximum about 2.6% 4 days after axotomy) and not significantly different from the control side throughout the time period studied. These data indicate that axotomy induces de novo synthesis of the CGRP beta-subtype in rubrospinal neurons and that the beta-CGRP is transported to the injury site through the rubrospinal tract. In addition, we studied the effect of the intracerebral injections of brain derived neurotrophic factor (BDNF). BDNF treatment fully reversed the severe cell atrophy that followed axotomy and increased the number of neurons labeled for beta-CGRP mRNA, but did not increase the percentage of rubrospinal neurons expressing beta-CGRP mRNA. Thus, topical application of BDNF does not have direct modulatory effect on CGRP induction in axotomized neurons in the red nucleus.

Behavioural effects of selective serotonin reuptake inhibitors following direct micro injection into the left red nucleus of the rat

The behavioural effects of selective serotonin reuptake inhibitors (paroxetine, sertraline, citalopram, fluvoxamine, fluoxetine) and reference compounds (N,N'-di(o-tolyl)guanidine, haloperidol, 3-(3-hydroxyphenyl)-N-(l-propyl)piperidine and chlorpromazine) were studied for their ability to produce dystonia and torticollis following direct micro injection into the left red nucleus of the rat, an area of the brain containing a high density of sigma2 receptors but relatively devoid of biogenic amine receptors. Each animal was monitored for abnormalities in posture and movement for a period of 30 min and then sacrificed 40 min following drug administation. Only fluvoxamine (100 nmol) and fluoxetine (100 nmol) elicited acute dystonic behaviour (1-5 min). The onset of dystonia was accompanied by facial spasticity, vacuous chewing movements and grooming behaviour which reflected the extent of dystonia. The dystonic behaviour following the direct intrarubal injection of fluvoxamine and fluoxetine suggest the possible activation of sigma2 receptors while citalopram, sertraline and paroxetine were without effect. The results of this study support the role of sigma2 receptors in the regulation and control of movement and coordination and provides preliminary evidence to suggest the in vivo activity of sigma receptors by fluoxetine and fluvoxamine.

Noradrenaline modifies the spontaneous spiking activity of red nucleus neurons in the rat by activation of alpha 2- and beta-adrenoceptors

We have investigated the effects of noradrenaline (NA) on the spontaneous firing activity of red nucleus (RN) neurons recorded extracellularly in anesthetized rats by using an in vivo electrophysiological technique. Microiontophoretic applications of NA (5-100 nA for 30 s) modified the background firing rate in 99 out of 124 neurons and three different patterns of response were observed in distinct cells. In 61% of the responding neurons NA decreased the mean firing rate, whereas 22% of the neurons responded to NA application with an increase of their spiking activity; in a smaller group of cells (17%) NA exerted a biphasic inhibitory/excitatory effect on the spontaneous firing rate. The effects of NA were reversible and dose-dependent. From histological examination, the neurons responding to NA with a purely inhibitory effect were scattered throughout the RN. On the other hand, the neurons responding to NA with an excitation were found to be more numerous in the dorso-medial part of the RN, whereas the neurons in which NA induced biphasic effects appeared to be segregated in the outer lateral portion of the RN. The alpha 2-adrenoceptor antagonist yohimbine completely blocked the inhibitory effect of NA but was unable to antagonize the excitatory response. In addition, the inhibitory effect of NA was mimicked by clonidine, a selective agonist of alpha 2-adrenoceptors; clonidine had no effect on those cells which responded to NA with an increase of the mean firing rate. The excitatory effect of NA was mimicked by the beta-receptor agonist isoprenaline and was antagonized by timolol, a selective antagonist of beta-adrenoceptors. Isoprenaline was ineffective in those cells in which NA exerted inhibitory responses. Taken together, our results indicate that the inhibitory effect of NA on the firing activity of rat RN neurons were mediated by alpha 2-adrenoceptors, whereas beta-adrenoceptors were responsible for the excitatory effects.

Dissociation of the motor effects of (+)-pentazocine from binding to sigma 1 sites

Radioligand binding and behavioral studies were conducted to determine whether a relationship existed between the motor effects produced by (+)-pentazocine and its binding to sigma sites. Scatchard analyses revealed decreased [3H](+)-pentazocine binding in middle aged rats (5-6 months old) compared to young adult rats (2-3 months old). However, there was no difference between the extent of circling behavior or dystonia produced by microinjection of (+)-pentazocine into the substantia nigra or red nucleus in the older animals compared to the young adult rats. There was also a significant decrease in [3H](+)-pentazocine binding in rats chronically treated with haloperidol. Again, however, despite the reduction in [3H](+)-pentazocine binding, there was no difference between the extent of dystonia produced by unilateral intrarubral microinjection of (+)-pentazocine into animals chronically treated with haloperidol vs. saline. The postural changes produced by (+)-pentazocine could not be attenuated with coadministration of the putative sigma receptor antagonist BD1047 (N-[2-(3,4-dichlorophenyl)ethyl]-N-methyl-2-(dimethylamino) ethylamine), or the opiate receptor antagonist naloxone. However, the (+)-opiate, (+)-nordihydrocodeinone, partially attenuated the postural effects of (+)-pentazocine, despite its very low affinity for sigma 1, sigma 2, or opiate receptors. Taken together with previous studies, the results suggest that [3H](+)-pentazocine is a potent and selective probe for sigma 1 binding sites, but the in vivo effects of (+)-pentazocine cannot be fully attributed to actions through these sites. Some of the in vivo effects of (+)-pentazocine appear to involve other binding sites that are not detected under the conditions normally used in in vitro assays.

BMY-14802 reversed the sigma receptor agonist-induced neck dystonia in rats

To clarify clinical roles of sigma receptor binding affinity of neuroleptics, neck dystonia induced by microinjection of sigma receptor ligands and neuroleptics into rat red nucleus was investigated. DTG and (+)-3-PPP, putative sigma receptor agonists, induced neck dystonia in dose-dependent and reversible manner. Haloperidol and perphenazine induced dystonia in the same way as sigma receptor agonists, whereas zotepine and (-)-sulpiride did not. The rank order of potency in induction of dystonia and sigma receptor affinity of these compounds showed positive correlation. Although BMY-14802 has a high affinity for sigma receptors, it never produced dystonia by itself. On the other hand, combined injection of BMY-14802 with DTG attenuated DTG-induced dystonia. Therefore, it is suggested that typical neuroleptics such as haloperidol act agonistic and atypical neuroleptics such as BMY-14802 act antagonistic at rubral sigma receptors in the induction of neck dystonia.

Neuronal responses to 5-hydroxytryptamine in the red nucleus of rats

The effects of microiontophoretic 5-hydroxytryptamine (5-HT) on the firing rate of red nucleus (RN) neurons were studied in urethane-anesthetized rats. The background discharge rate of almost all the neurons tested (97%) was modified by 5-HT, and generally increased (89%). Responses were dose dependent. Twenty-three percent of the excitatory responses were preceded by a short inhibitory phase. No significant difference in the effect of 5-HT was found between those RN neurons that project to the spinal cord and those that do not The excitatory responses to 5-HT were blocked or greatly reduced by the 5-HT antagonists methysergide and ketanserin, and were even reversed in some cases. The 5-HT2/5-HT1A antagonist spiperone, in small doses, also blocked the transient inhibitory phases in addition to the excitatory effects. In RN neurons exhibiting a short-lasting inhibition in the response to 5-HT, the 5-HT1A agonist 8-hydroxy-2(di-n-propyl-amino)tetralin (8-OH-DPAT) induced inhibitory effects. These results support the hypothesis that 5-HT exerts control throughout the RN, mostly by acting on 5-HT2 receptors. Furthermore, an influence of this amine on the electrical activity of small groups of RN neurons by 5-HT1A receptors, and eventually by different mechanisms, appears probable. The functional significance of serotoninergic control of RN neuronal activity is discussed.

Peripheral nicotine administration increases rubral firing rates in the urethane-anesthetized rat

The presence of cholinergic input to the red nucleus (RN) in the cat is demonstrated by choline acetyltransferase (ChAT) staining; however, it is unclear what effect this cholinergic input has on neurons of the RN. Further, the presence of cholinergic neurons in the rat RN has been the subject of controversy. The present study examined the effects of intravenous injections of S(-)-nicotine tartrate (62.5-250 micrograms/kg) on the firing rate of rubral neurons. Dose-dependent increases in firing rates were observed which were blocked by pre-treatment with the nicotinic antagonist, mecamylamine hydrochloride. Smaller consistent increases were found after pretreatment with 62.5 micrograms/kg or 125 micrograms/kg doses of nicotine than were observed following the initial administration, suggesting a desensitizing response typical of nicotinic receptors.

Possible involvement of nitric oxide in red nucleus stimulation-induced analgesia in the rat

There is considerable evidence that nitric oxide (NO) plays a role in synaptic transmission in both central and peripheral nervous systems. Recent studies have suggested the involvement of the L-arginine-NO pathway in nociceptive transmission/modulation. Electrical stimulation of the red nucleus in the rat evokes potent analgesia. Microinjection of different concentrations of L-arginine (1 nmol-1 mumol), but not of D-arginine, produced quick and long-lasting analgesia. Pretreatment with N-nitro-L-arginine methyl ester (1 mumol), a nitric oxide synthase inhibitor, significantly prevented L-arginine-induced analgesia. Further, pretreatment of animals with methylene blue, a known guanylate cyclase inhibitor, also attenuated the development of analgesia. Our results suggest that L-arginine caused production of NO, which in turn activated the red nucleus analgesic system.

Effect of zolpidem on gamma-aminobutyric acid (GABA)-induced inhibition predicts the interaction of ethanol with GABA on individual neurons in several rat brain regions

Previous investigations have suggested a relationship between zolpidem binding within specific brain regions and the ability of ethanol or zolpidem to enhance gamma-aminobutyric acid (GABA)-induced inhibition. The purpose of the present study was to extend our electrophysiological analysis to additional brain sites with high levels of zolpidem binding. In the brain regions chosen, red nucleus and globus pallidus, GABA-induced inhibition was shown to be enhanced by either ethanol or zolpidem on some, but not all, neurons. These findings led to the hypothesis that the effect of zolpidem on GABA-induced inhibition would predict the action of ethanol on responses to GABA for that neuron. When zolpidem and ethanol were applied individually to the same neurons in the red nucleus and globus pallidus, those neurons sensitive to zolpidem enhancement of GABA also were sensitive to ethanol. Conversely, if zolpidem did not enhance responses to GABA, ethanol did not enhance responses to GABA at these brain sites. A similar relationship between the abilities of zolpidem and ethanol to enhance GABA-induced inhibition was obtained in 90% of the neurons studied in the medial septum/diagonal band and ventral pallidum. These studies provide further support for the contention that the zolpidem-sensitive GABAA-benzodiazepine isoreceptor also responds to ethanol. Finally, the expression of GABAA subunit mRNAs was analyzed by polymerase chain reaction from micropunches of several brain regions that contain zolpidem binding sites and exhibit sensitivity to ethanol. Polymerase chain reaction analysis proved more sensitive than in situ hybridization in the detection of receptor subunit mRNAs. Several subunits (alpha 1, alpha 2, alpha 3, beta 2, beta 3 and gamma 2) were common to all brain regions in which ethanol and zolpidem enhanced GABA responses. GABAA receptor alpha 4/5, alpha 6, beta 1, gamma 1, gamma 3 and delta subunits were not consistently expressed in association with the presence of zolpidem binding. These data are consistent with the view that one native GABAA receptor to which zolpidem binds, and on which ethanol acts, contains the GABAA receptor subunits alpha 1, beta 2 and gamma 2; however, the present investigation did not preclude the possibility that other subunit combinations can contribute to ethanol and zolpidem enhancement of responses to GABA.

NMDA receptor blockade rescues Clarke's and red nucleus neurons after spinal hemisection

Hemisection of the adult rat spinal cord at T9 transects the ascending ipsilateral axons of Clarke's nucleus (CN) neurons and the descending contralateral axons of red nucleus (RN) neurons. Eight weeks following axotomy, 30% of CN neurons and 22% of RN neurons die. Since both nuclei receive glutamatergic input, we wished to examine the possibility that glutamatergic excitotoxicity contributes to axotomy-induced neuronal death in these nuclei. To test this we studied the effects of administration of the NMDA receptor antagonist MK-801 on cell survival after axotomy. When 1 mg/kg body weight MK-801 is administered subcutaneously every day for 1-8 weeks to hemisected rats, cell death is prevented. Treatment with 0.5 mg/kg body weight MK-801 over the same time periods results in only partial rescue of axotomized neurons. Paradoxically, when 1 mg/kg MK-801 administration is restricted to the first week of an 8 week survival period, cell death in both the RN and CN is greatly exaggerated over the cell loss found in saline-treated animals. Withdrawal of 1 mg/kg MK-801 after 1 week of administration induces the loss of 92% of CN neurons, which is 63% greater than that occurring after axotomy alone. If, however, 1 mg/kg MK-801 is withdrawn after 2 weeks post-axotomy in the RN and 3 weeks postaxotomy in CN, all axotomized neurons survive. This rescue is found at 6 months postsurgery, the longest survival period studied, and therefore appears to be permanent. These results suggest that glutamatergic afferent input contributes significantly to the death of axotomized red nucleus and Clarke's nucleus neurons via NMDA receptors located on these neurons.

Neurotrophic factors prevent the death of CNS neurons after spinal cord lesions in newborn rats

The aim of this study was to determine if the exogenous administration of neurotrophic factors can rescue immature axotomized CNS neurons in vivo. After spinal cord hemisection in newborn rats, the exogenous administration of neurotrophic factors brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3) and nerve growth factor (NGF), prevents the retrograde cell death of axotomized red nucleus neurons (and other brain stem spinal neurons) in vivo. Rescue of red nucleus neurons was maintained in the presence of BDNF, but only transiently maintained by NT-3 and NGF. Neurons within the nucleus dorsalis (Clarke's nucleus) of the spinal cord are also axotomized by this lesion. The application of exogenous NT-3, but not NGF or BDNF, rescued Clarke's nucleus neurons. These observations indicate that neurotrophic factors play a crucial role in the survival of CNS neurons in vivo during development and after injury. Furthermore, these results indicate that particular populations of neurons are dependent upon specific neurotrophic support after injury.

Pharmacological characterisation of excitatory synaptic transmission in the cat red nucleus in vivo

Extracellular recordings were made from the magnocellular neurones of the red nucleus (mRN) in anaesthetised cats. A study was made of the effects of selective excitatory amino acid receptor antagonists on excitatory monosynaptic responses evoked from the sensorimotor cortex (SMC) and cerebellar interpositus nucleus (IPN). Iontophoretically applied CNQX and NBQX antagonised both SMC and IPN responses whereas, D-AP5 inhibited the SMC response but was ineffective to the IPN. At currents that selectively antagonised NMDA responses, CPPene had no effect on either SMC or IPN responses. 7-chlorokynurenate inhibited both SMC and IPN responses but required currents that antagonised both AMPA and NMDA responses and was therefore acting in a non-selective manner. Iontophoretically applied glycine was inhibitory to both agonist and synaptic responses, whilst D-serine potentiated NMDA responses but did not enhance monosynaptic responses of the SMC. However in the presence of either 7-chlorokynurenate or high currents of CNQX that reduced the SMC synaptic activation of the mRN neurones, D-serine attenuated the inhibitory action of these antagonists. It is concluded that monosynaptic responses from the SMC are mediated by both NMDA and non-NMDA receptors whereas the monosynaptic responses evoked from the IPN are mediated only by non-NMDA receptors. The lack of effect of CPPene is consistent with the postulate that two NMDA receptor subtypes are present on mRN neurones.

Effect of nimodipine or methylprednisolone on recovery from acute experimental spinal cord injury in rats

The purpose of the present study was to examine the behavioral, electrophysiologic, and anatomic responses to nimodipine or methylprednisolone treatment of acute experimental spinal cord injury. Four groups of rats were injured at T1 by compressing the cord with a 52-g clip for 1 minute. The treatments were begun 15 minutes after injury, and the animals were observed thereafter for 8 weeks. Nimodipine 0.02 mg/kg/h intravenously (iv) for 8 hours with adjuvant albumen volume expansion, followed by 20 mg/kg nimodipine enterally three times per day for 7 days, produced a moderately better composite score comprising four endpoint parameters than the other treatments which consisted of nimodipine iv for 8 hours only, methylprednisolone 30 mg/kg iv bolus followed by 5.4 mg/kg/h iv for 8 hours, or control.