Increasing CNS norepinephrine levels by the precursor L-DOPS facilitates beam-walking recovery after sensorimotor cortex ablation in rats

Effects of Manipulation of Noradrenergic Activities on the Expression of Dopaminergic Phenotypes in Aged Rat Brains

This study investigated the effects of the pharmacological manipulation of noradrenergic activities on dopaminergic phenotypes in aged rats. Results showed that the administration of L-threo-3,4-dihydroxyphenylserine (L-DOPS) for 21 days significantly increased the expression of tyrosine hydroxylase (TH) and dopamine transporter (DAT) in the striatum and substantia nigra (SN) of 23-month-old rats. Furthermore, this treatment significantly increased norepinephrine/DA concentrations in the striatum and caused a deficit of sensorimotor gating as measured by prepulse inhibition (PPI). Next, old rats were injected with the α2-adrenoceptor antagonist 2-methoxy idazoxan or β2-adrenoceptor agonist salmeterol for 21 days. Both drugs produced similar changes of TH and DAT in the striatum and SN. Moreover, treatments with L-DOPS, 2-methoxy idazoxan, or salmeterol significantly increased the protein levels of phosphorylated Akt in rat striatum and SN. However, although a combination of 2-methoxy idazoxan and salmeterol resulted in a deficit of PPI in these rats, the administration of 2-methoxy idazoxan alone showed an opposite behavioral change. The in vitro experiments revealed that treatments with norepinephrine markedly increased mRNAs and proteins of ATF2 and CBP/p300 and reduced mRNA and proteins of HDAC2 and HDAC5 in MN9D cells. A ChIP assay showed that norepinephrine significantly increased CBP/p300 binding or reduced HDAC2 and HDAC5 binding on the TH promoter. The present results indicate that facilitating noradrenergic activity in the brain can improve the functions of dopaminergic neurons in aged animals. While this improvement may have biochemically therapeutic indication for the status involving the degeneration of dopaminergic neurons, it may not definitely include behavioral improvements, as indicated by using 2-methoxy idazoxan only.

Droxidopa alters dopamine neuron and prefrontal cortex activity and improves attention-deficit/hyperactivity disorder-like behaviors in rats

Finding alternative treatments for attention-deficit/hyperactivity disorder (ADHD) is crucial given the safety and efficacy problems of current ADHD medications. Droxidopa, also known as L-threo-dihydroxyphenylserine (L-DOPS), is a norepinephrine prodrug that enhances brain norepinephrine and dopamine levels. In this study, we used electrophysiological tests to examine effects of L-DOPS on the prefrontal cortex (PFC) and dopamine neurons in the ventral tegmental area. We also conducted behavioral tests to assess L-DOPS' effects on ADHD-like behaviors in rats. In chloral hydrate-anesthetized rats, PFC local field potentials oscillated between the active, depolarized UP state and the hyperpolarized DOWN state. Mimicking the effect of d-amphetamine, L-DOPS, given after the peripheral amino acid decarboxylase inhibitor, benserazide (BZ), increased the amount of time the PFC spent in the UP state, indicating an excitatory effect of L-DOPS on PFC neurons. Like d-amphetamine, L-DOPS also inhibited dopamine neurons, an effect significantly reversed by the D2-like receptor antagonist raclopride. In the behavioral tests, BZ + L-DOPS improved hyperactivity, inattention and impulsive action of the adolescent spontaneously hypertensive rat (SHR/NCrl), well-validated animal model of the combined type of ADHD. BZ + L-DOPS also reduced impulsive choice and impulsive action of Wistar rats, but did not ameliorate the inattentiveness of Wistar Kyoto rats (WKY/NCrl), proposed model of the ADHD-predominantly inattentive type. In conclusion, L-DOPS produced effects on the PFC and dopamine neurons characteristic of drugs used to treat ADHD. BZ + L-DOPS ameliorated ADHD-like behaviors in rats suggesting its potential as an alternative ADHD treatment.

Interdependent adrenergic receptor regulation of Arc and Zif268 mRNA in cerebral cortex

Norepinephrine is a neurotransmitter that signals by stimulating the α1, α2 and β adrenergic receptor (AR). We determined the role of these receptors in regulating the immediate early genes, Activity Regulated Cytoskeleton Associated Protein (Arc) and Zif268 in the rat cerebral cortex. RX821002, an α2-AR antagonist, produced Arc and Zif268 elevations across cortical layers. Next we examined the effects of delivering RX821002 with an α1-AR antagonist, prazosin, and a β-AR antagonist, propranolol. RX821002 given with a prazosin and propranolol cocktail, or with each of these antagonists individually, decreased Arc and Zif268 to saline-treated control levels in most cortical layers. Arc and Zif268 levels were also similar to saline-treated control levels when rats were given a prazosin and propranolol cocktail alone, or when each of these antagonists were delivered individually. Taken together, these data reveal that α2-AR uniquely exert a tonic inibitory regulation of both Arc and Zif268 compared to α1 and β-AR. However, the ability of RX821002 to increase Arc and Zif268 is interdependent with α1 and β-AR signaling.

Sensorimotor recovery from cortical injury is accompanied by changes on norepinephrine and serotonin levels in the dentate gyrus and pons

Monoamines such as norepinephrine (NE) and serotonin (5-HT) have shown to play an important role in motor recovery after brain injury. The effects elicited by these neurotransmitters have been reported as distal from the area directly affected. Remote changes may take place over minutes to weeks and play an important role in post-stroke recovery. However, the mechanisms involved in spontaneous recovery have not been thoroughly delineated. Therefore, we determined the NE and 5-HT content, in the pons and hippocampal dentate gyrus (DG) as well as motor deficit and spontaneous activity in rats after 3, 10 and 20 days cortical iron injection. Three days post-lesion the pontine NE content diminished, this effect was accompanied by deficient spontaneous activity and impaired sensorimotor evaluation. Ten and twenty days after lesion the NE levels were similar to those of control group, and animals also showed behavioral recovery. Monoamines content on DG 3 days post-lesion showed no differences as compared to controls. Interestingly, ten and twenty days after cortical injury, animals showed increased NE and 5-HT. These results suggest that behavioral recovery after brain damage involve changes on monoamines levels on DG, an important structure to plastic processes. In addition, the results herein support evidence to propose these neurotransmitters as key molecules to functional recovery in the central nervous system.

Is there a role for vagus nerve stimulation therapy as a treatment of traumatic brain injury?

This paper aims to review the current literature on vagus nerve stimulation (VNS) use in animal models of traumatic brain injury (TBI) and explore its potential role in treatment of human TBI. A MEDLINE search yielded four primary papers from the same group that demonstrated VNS mediated improvement following fluid percussion models of TBI in rats, seen as motor and cognitive improvements, reduction of cortical oedema and neuroprotective effects. The underlying mechanisms are elusive and authors attribute these to attenuation of post traumatic seizures, a noradrenergic mechanism and as yet undetermined mechanisms. Reviewing and elaborating on these ideas, we speculate other potential mechanisms including attenuation of peri-infarct depolarisations, attenuation of glutamate mediated excitotoxicity, stabilisation of intracranial pressure, enhancement of synaptic plasticity, upregulation of endogenous neurogenesis and anti-inflammatory effects may have a role. Although this data unequivocally shows that VNS improves outcome from TBI in animal models, it remains to be determined if these findings translate clinically. Further studies are warranted.

Impact of pharmacological treatments on cognitive and behavioral outcome in the postacute stages of adult traumatic brain injury: a meta-analysis

Pharmacological treatments that are administered to adults in the postacute stage after a traumatic brain injury (TBI) (≥4 weeks after injury) have the potential to reduce persistent cognitive and behavioral problems. While a variety of treatments have been examined, the findings have yet to be consolidated, hampering advances in the treatment of TBI. A meta-analysis of research that has investigated the cognitive and behavioral effects of pharmacological treatments administered in the later stage after TBI was therefore conducted. The PubMed and PsycINFO databases were searched, and Cohen d effect sizes, percent overlap, and failsafe N statistics were calculated for each treatment. Both randomized controlled trials and open-label studies (prospective and retrospective) were included. Nineteen treatments were investigated by 30 independent studies, comprising 395 participants with TBI in the treatment groups and 137 control subjects. When treated in the postacute period, 1 dopaminergic agent (methylphenidate) improved behavior (anger/aggression, psychosocial function) and 1 cholinergic agent (donepezil) improved cognition (memory, attention). In addition, when the injury-to-treatment interval was broadened to include studies that administered treatment just before the postacute period, 2 dopaminergic agents (methylphenidate, amantadine) showed clinically useful treatment benefits for behavior, whereas 1 serotonergic agent (sertraline) markedly impaired cognition and psychomotor speed.

Regulation of MCP-1 production in brain by stress and noradrenaline-modulating drugs

While it is accepted that noradrenaline (NA) reduction in brain contributes to the progression of certain neurodegenerative diseases, the mechanisms through which NA exerts its protective actions are not well known. We previously reported that NA induced production of monocyte chemoattractant protein (MCP-1/CCL2) in cultured astrocytes mediated some of the neuroprotective actions of NA. We have now examined the regulation of MCP-1 production in vivo. Treatment of mice with the NA precursor l-threo-3,4-dihydroxyphenylserine induced the production of MCP-1 in astrocytes. In contrast, exposure to stress (a process known to elevate brain NA levels) produced only a moderate increase of MCP-1 because of the inhibitory activity of glucocorticoids released during the stress response. Similarly, corticosterone treatment of astrocytes caused a reduction of constitutive as well as the NA-induced MCP-1 production. When stressed rats had the production of glucocorticoids blocked by the selective inhibitor metyrapone, a large increase of MCP-1 concentration was observed in cortex, whereas propranolol (a beta adrenergic receptor blocker) avoided modifications of MCP-1 after stress. Desipramine (an inhibitor of NA reuptake) also caused an increase of MCP-1 in cortex. These data suggest that some phenomena caused by the alteration of NA or glucocorticoids could be mediated by MCP-1.

Increased extracellular concentrations of norepinephrine in cortex and hippocampus following vagus nerve stimulation in the rat

The vagus nerve is an important source of afferent information about visceral states and it provides input to the locus coeruleus (LC), the major source of norepinephrine (NE) in the brain. It has been suggested that the effects of electrical stimulation of the vagus nerve on learning and memory, mood, seizure suppression, and recovery of function following brain damage are mediated, in part, by the release of brain NE. The hypothesis that left vagus nerve stimulation (VNS) at the cervical level results in increased extracellular NE concentrations in the cortex and hippocampus was tested at four stimulus intensities: 0.0, 0.25, 0.5, and 1.0 mA. Stimulation at 0.0 and 0.25 mA had no effect on NE concentrations, while the 0.5 mA stimulation increased NE concentrations significantly in the hippocampus (23%), but not the cortex. However, 1.0 mA stimulation significantly increased NE concentrations in both the cortex (39%) and hippocampus (28%) bilaterally. The increases in NE were transient and confined to the stimulation periods. VNS did not alter NE concentrations in either structure during the inter-stimulation baseline periods. No differences were observed between NE levels in the initial baseline and the post-stimulation baselines. These findings support the hypothesis that VNS increases extracellular NE concentrations in both the hippocampus and cortex.

Pontine and cerebellar norepinephrine content in adult rats recovering from focal cortical injury

Norepinephrine (NE) plays an important role in motor recovery after brain damage. Most studies concerning NE activity have been performed in the cerebellum, while the role of the pons, the site where the norepinephrinergic locus coeruleus is located, has not yet been elucidated. For this work, we studied the changes in cerebellar and pontine NE content in sham-operated (n = 17), motor cortex injured (n = 6) and recovered rats (n = 12). Motor effects were assessed by means of footprint analysis and sensorimotor evaluation. It was found that after cortical brain damage, the stride length decreases while the stride angle increases after 6 h post-surgery, while the sensorimotor evaluation showed an increase in the motor deficit. Recovery was observed after 24 h. NE content increased in the pons after 6 h and returned to normal levels in recovered rats, with no significant changes observed in the cerebellum. Based on the functional remote inhibition, it is possible that NE exerts an autoinhibitory effect in the pons after motor cortical ablation. On the other hand, the absence of an effect in the cerebellum suggests that cerebellar NE activity related to damage and/or recovery is limited to discrete areas of the structure.

Delayed, post-injury treatment with aniracetam improves cognitive performance after traumatic brain injury in rats

Chronic cognitive impairment is an enduring aspect of traumatic brain injury (TBI) in both humans and animals. Treating cognitive impairment in the post-traumatic stages of injury often involves the delivery of pharmacologic agents aimed at specific neurotransmitter systems. The current investigation examined the effects of the nootropoic drug aniracetam on cognitive recovery following TBI in rats. Three experiments were performed to determine (1) the optimal dose of aniracetam for treating cognitive impairment, (2) the effect of delaying drug treatment for a period of days following TBI, and (3) the effect of terminating drug treatment before cognitive assessment. In experiment 1, rats were administered moderate fluid percussion injury and treated with vehicle, 25, or 50 mg/kg aniracetam for 15 days. Both doses of aniracetam effectively reduced injury-induced deficits in the Morris water maze (MWM) as measured on postinjury days 11-15. In experiment 2, injured rats were treated with 50 mg/kg aniracetam or vehicle beginning on day 11 postinjury and continuing for 15 days. MWM performance, assessed on days 26-30, indicates that aniracetam-treated animals performed as well as sham-injured controls. In experiment 3, animals were injured and treated with aniracetam for 15 days. Drug treatment was terminated during MWM testing on postinjury days 16-20. In this experiment, aniracetam-treated rats did not perform better than vehicle-treated rats. The results of these experiments indicate that aniracetam is an effective treatment for cognitive impairment induced by TBI, even when treatment is delayed for a period of days following injury.

Electrical stimulation of the vagus nerve enhances cognitive and motor recovery following moderate fluid percussion injury in the rat

Intermittent, chronically delivered electrical stimulation of the vagus nerve (VNS) is an FDA-approved procedure for the treatment of refractory complex/partial epilepsy in humans. Stimulation of the vagus has also been shown to enhance memory storage processes in laboratory rats and human subjects. Recent evidence suggests that some of these effects of VNS may be due to the activation of neurons in the nucleus locus coeruleus resulting in the release of norepinephrine (NE) throughout the neuraxis. Because antagonism of NE systems has been shown to delay recovery of function following brain damage, it is possible that enhanced release of NE in the CNS may facilitate recovery of function. To evaluate this hypothesis the lateral fluid percussion injury (LFP) model of traumatic brain injury was used and a variety of motor and cognitive behavioral tests were employed to assess recovery in pre-trained stimulated, control, and sham-injured laboratory rats. Two hours following moderate LFP, vagus nerve stimulation (30.0-sec trains of 0.5 mA, 20.0 Hz, biphasic pulses) was initiated. Stimulation continued in each animal's home cage at 30-min intervals for a period of 14 days, with the exception of brief periods when the animals were disconnected for behavioral assessments. Motor behaviors were evaluated every other day following LFP and tests included beam walk, locomotor placing, and skilled forelimb reaching. In each measure an enhanced rate of recovery and /or level of final performance was observed in the VNS-LFP animals compared to nonstimulated LFP controls. Behavior in the Morris water maze was assessed on days 11-14 following injury. Stimulated LFP animals showed significantly shorter latencies to find the hidden platform than did controls. Despite these behavioral effects, neurohistological examination did not reveal significant differences in lesion extent, density of fluorojade positive neurons, reactive astrocytes or numbers of spared neurons in the CA3 subarea of the hippocampus, at least at the one time point studied 15 days post-injury. These results support the idea that vagus nerve stimulation enhances the neural plasticity that underlies recovery of function following brain damage and provides indirect support for the hypothesis that enhanced NE release may mediate the effect. Importantly, since VNS facilitated both the rate of recovery and the extent of motor and cognitive recovery, these findings suggest that electrical stimulation of the vagus nerve may prove to be an effective non-pharmacological treatment for traumatic brain injury.

Noradrenergic mechanisms in neurodegenerative diseases: a theory

A deficiency in the noradrenergic system of the brain, originating largely from cells in the locus coeruleus (LC), is theorized to play a critical role in the progression of a family of neurodegenerative disorders that includes Parkinson's disease (PD) and Alzheimer's disease (AD). Consideration is given here to evidence that several neurodegenerative diseases and syndromes share common elements, including profound LC cell loss, and may in fact be different manifestations of a common pathophysiological process. Findings in animal models of PD indicate that the modification of LC-noradrenergic activity alters electrophysiological, neurochemical and behavioral indices of neurotransmission in the nigrostriatal dopaminergic system, and influences the response of this system to experimental lesions. In models related to AD, noradrenergic mechanisms appear to play important roles in modulating the activity of the basalocortical cholinergic system and its response to injury, and to modify cognitive functions including memory and attention. Mechanisms by which noradrenaline may protect or promote recovery from neural damage are reviewed, including effects on neuroplasticity, neurotrophic factors, neurogenesis, inflammation, cellular energy metabolism and excitotoxicity, and oxidative stress. Based on evidence for facilitatory effects on transmitter release, motor function, memory, neuroprotection and recovery of function after brain injury, a rationale for the potential of noradrenergic-based approaches, specifically alpha2-adrenoceptor antagonists, in the treatment of central neurodegenerative diseases is presented.

Differential Concentration-Dependent Effects of Prolonged Norepinephrine Infusion on Intraparenchymal Hemorrhage and Cortical Contusion in Brain-Injured Rats

Under clinical conditions catecholamines are infused to elevate cerebral perfusion pressure and improve impaired posttraumatic cerebral microcirculation. This, however, is associated with the risk of additional hemorrhage in the acute phase following traumatic brain injury. In the present study we investigated the dose-dependent effects of prolonged norepinephrine infusion on arterial blood pressure, blood glucose, and structural damage in brain-injured rats. At 4 h following induction of a focal cortical contusion (CCI), 40 rats were randomized to receive low (0.15), medium (0.3), or high dose (1 microg/kg/min) norepinephrine. Control rats were given equal volume of NaCl. Norepinephrine and NaCl were infused intravenously via Alzet osmotic pumps for 44 h. Mean arterial blood pressure (MABP), blood gases and blood glucose were determined before, at 4, 24, 48 h after CCI in repeatedly anesthetized rats (n = 28). Systolic arterial blood pressure (SABP) was measured using the tail cuff method in awake, restrained rats (n = 12). Cortical contusion and intraparenchymal hemorrhage volume were quantified at 48 h in all rats. MABP determined in anesthetized rats was only marginally increased. SABP was significantly elevated during infusion of medium and high dose norepinephrine in awake rats, exceeding 140 mm Hg. Medium and high dose norepinephrine significantly increased cortical hemorrhage by 157% and 142%, without increasing the cortical contusion volume. Low dose norepinephrine significantly reduced the cortical contusion by 44%. Norepinephrine aggravates the underlying brain damage during the acute posttraumatic phase. Future studies are needed to determine the least deleterious norepinephrine concentration.

The morphological and neurochemical effects of diffuse brain injury on rat central noradrenergic system

The central noradrenergic system is widely distributed throughout the brain and is closely related to spontaneous motility and level of consciousness. The study presented here evaluated the morphological as well as neurochemical effects of diffuse brain injury on the central noradrenergic system in rat. Adult male Sprague-Dawley rats were subjected to impact-acceleration brain injury produced with a weight-drop device. Morphological changes in locus coeruleus (LC) neurons were examined by using immunohistochemistry for dopamine-beta-hydroxylase, and norepinephrine (NE) turnover in the cerebral cortex was measured by high performance liquid chromatography with electrochemical detection. The size of LC neurons increased by 11% 24 h after injury but had decreased by 27% seven days after injury. Axons of noradrenergic neurons were swollen 24 h and 48 h after injury but the swelling had dwindled in seven days. NE turnover was significantly reduced seven days after injury and remained at a low level until eight weeks after injury. These results suggest that focal impairment of axonal transport due to diffuse brain injury causes cellular changes in LC and that the neurochemical effect of injury on the central noradrenargic system lasts over an extended period of time. Chronic suppression of NE turnover may explain the sustained behavioral and psychological abnormalities observed in a clinical situation.

Influence of norepinephrine and dopamine on cortical perfusion, EEG activity, extracellular glutamate, and brain edema in rats after controlled cortical impact injury

Following traumatic brain injury, catecholamines given to ameliorate cerebral perfusion may induce brain damage via cerebral arteriolar constriction and increased neuronal excitation. In the present study the acute effects of norepinephrine and dopamine on pericontusional cortical perfusion (rCBF), electroencephalographic (EEG) activity, extracellular glutamate, and brain edema were investigated in rats following controlled cortical impact injury (CCI). rCBF, cerebral perfusion pressure (CPP), EEG activity, and glutamate were determined before, during, and after infusing norepinephrine or dopamine, increasing MABP to 120 mm Hg for 90 min at 4 h after CCI. Control rats received physiological saline. At 8 h after CCI, hemispheric swelling and water content were determined gravimetrically. Following CCI, rCBF was significantly decreased. In parallel to elevating MABP and CPP, rCBF was significantly increased by norepinephrine and dopamine, being mostly pronounced with norepinephrine (+44% vs. +29%). In controls, rCBF remained diminished (-45%). EEG activity was significantly increased by norepinephrine and dopamine, while pericontusional glutamate was only elevated by norepinephrine (28 +/- 6 vs. 8 +/- 4 microM). Brain edema was not increased compared to control rats. Despite significantly increasing MABP and CPP to the same extent, norepinephrine and dopamine seem to differentially influence pericontusional cortical perfusion and glutamatergic transmission. In addition to the pressure-passive increase in CPP local cerebral effects seem to account for the sustained norepinephrine-induced increase in pericontusional cortical perfusion. The significantly elevated pericontusional glutamate concentrations in conjunction with the increased EEG activity suggest a sustained metabolically driven increase in cortical perfusion during norepinephrine infusion.

Behavior of fluorinated analogs of L-(3,4-dihydroxyphenyl)alanine and L-threo-(3,4-dihydroxyphenyl)serine as substrates for Dopa decarboxylase

We have determined the kinetic parameters for Dopa decarboxylase (DDC) of three ring-fluorinated analogs of 3,4-dihydroxyphenylalanine (Dopa). The rank order of catalytic efficiency of decarboxylation (k(cat)/K(m)) is Dopa>6-F-Dopa>2-F-Dopa>5-F-Dopa. This rank is consistent with previous in vivo and in vitro studies which indicate that, of the fluorinated analogs, 6-F-Dopa has pharmacokinetics that are most suited for positron emission tomographic (PET) evaluation of dopamine function. The effectiveness of PET as a diagnostic tool, the convenient half-life of (18)F (110 min) and the favorable pharmacokinetics of 6-[(18)F]FDOPA have combined to make this an extremely valuable reagent to study dopaminergic activity. The reactions of the related fluorinated DOPS analogs show that, while 6-F-threo-3,4-(dihydroxyphenyl)serine (DOPS) is decarboxylated at approximately the same rate as the non-fluorinated substrate, 2-F-threo-DOPS is not converted into the corresponding amine. In both cases a Pictet-Spengler condensation with the pyridoxal 5(')-phosphate (PLP) cofactor occurs to produce tetrahydroisoquinolines. Condensation of fluorinated catecholamines and catechol amino acids with endogenous aldehydes will be investigated as an approach to study possible mechanisms of L-Dopa-linked neurotoxicity.

Extradural compression of sensorimotor cortex: a useful model for studies on ischemic brain damage and neuroprotection

Behavioral and morphological changes were examined for up to 9 days after moderate cerebral ischemia caused by slow compression of a specific brain area in the sensorimotor cortex of Sprague-Dawley rats. Functional deficits after the cerebral ischemia were assessed by daily beam-walking tests, whereas morphological changes were verified using Nissl staining on day 1, 2, 3, 5, and 9, respectively. Rats exposed to cerebral ischemia displayed impaired beam walking performance. Mild hypothermia prevented both the compression-produced functional deficits and the brain damage. Younger (5 weeks) animals showed less neurological deficits than older (9 weeks) animals. Histological examination revealed a pronounced increase in the number of injured pyramidal neurons from day 1 to day 3 in the primarily damaged brain region. Between day 3 and day 5, the number of injured cells remained constant, whereafter there was a slow decline of thionin-positive neurons as examined on day 9. The noncompetitive NMDA receptor antagonist, dizocilpine (MK-801; 3 mg/kg, i.p.), did not alter the neurological impairment on day 1, but improved thereafter the rate of functional recovery and reduced the number of damaged cells. The AMPA receptor antagonist, LY326325 (15 or 30 mg/kg; i.p.), dose-dependently diminished the neurological deficits on day 1, enhanced the rate of recovery, and reduced the number of injured neurons over time. Our data suggest that short-lasting extradural compression of a well-defined brain area in the sensorimotor cortex is a highly reproducible model with a high success rate for the study of functional and morphological consequences after cerebral ischemia as well as for the evaluation of the therapeutic potential of novel, neuroprotective pharmacological agents.

The norepinephrine precursor L-threo-3,4-dihydroxyphenylserine facilitates motor recovery in chronic stroke patients

L-threo-3, 4-dihydroxyphenylserine (L-DOPS) is a precursor of norepinephrine. We reported that administration of L-DOPS to rats with ablation of the right sensorimotor cortex results in functional recovery from deficits in beam-walking performance. We al so reported that improvement in Fugl-Meyer Score (FMS) was significantly higher in an L-DOPS-treated group of chronic neurologically stable stroke patients than in a control group for 2 days. In the present study, 27 patients who had suffered from stroke more than one month previously and had exhibited no improvement in neurological deficits for at least one week were administered 300mg/day L-DOPS for 28 days with rehabilitation. FMS improved by 4.4 points (P< 0.001), 10m gait time was shortened by 16% (P< 0.001) and the cerebral blood flow of the lesion was increased (P< 0.03), after 28 days of drug administration. These findings suggest that L-DOPS is effective in restoring neurological deficit, which does not usually recover when only treated with rehabilitation therapy.

Effect of levodopa in combination with physiotherapy on functional motor recovery after stroke: a prospective, randomised, double-blind study

BACKGROUND

Functional disability is generally caused by hemiplegia after stroke. Physiotherapy used to be the only way of improving motor function in such patients. However, administration of amphetamines in addition to exercise improves motor recovery in animals, probably by increasing the concentration of norepinephrine in the central nervous system. Our aim was to ascertain whether levodopa could enhance the efficacy of physiotherapy after hemiplegia.

METHODS

We did a prospective, randomised, placebo-controlled, double-blind study in which we enrolled 53 primary stroke patients. For the first 3 weeks patients received single doses of levodopa 100 mg or placebo daily in combination with physiotherapy. For the second 3 weeks patients had only physiotherapy. We quantitatively assessed motor function every week with Rivermead motor assessment (RMA).

FINDINGS

Six patients were excluded from analyses because of non-neurological complications. Motor recovery was significantly improved after 3 weeks of drug intervention in those on levodopa (RMA improved by 6.4 points) compared with placebo (4.1), and the result was independent of initial degree of impairment (p<0.004). The advantage of the levodopa group was maintained at study endpoint 3 weeks after levodopa was stopped. At the end of the study the total RMA score gain for the levodopa group was 8.2 points compared with 5.7 in the placebo group (p=0.020).

INTERPRETATION

A single dose of levodopa is well tolerated and, when given in combination with physiotherapy, enhances motor recovery in patients with hemiplegia. In view of its minimal side-effects, levodopa will be a possible add- on during stroke rehabilitation.

Induction of heat shock proteins and motor function deficits after focal cerebellar injury

A weight drop model of focal cerebellar injury was used to identify heat shock protein induction and motor function deficits in the anesthetized, adult male, Sprague-Dawley rat. All animals were trained on a beam walking test prior to surgery. Groups of animals received severe, mild or sham weight drop injury to the lateral/paravermal region of the cerebellum. The mild and sham-injured animals showed no motor deficits in the beam walking test, whereas animals with severe cerebellar injury showed significant motor deficits in the beam walking test that approached recovery of motor function 20 days after injury. Following severe injury, induction of heat shock protein of 27kDa was observed in Purkinje cells and in neurons of the deep cerebellar nuclei, as well as Bergmann glial cells, glial cells located in the granule cell layer and the underlying white matter. Following mild injury, heat shock protein of 27kDa induction was observed in Purkinje cells and glial cells, but not in neurons of the deep cerebellar nuclei. The labeled Purkinje cells were widely distributed in the ipsilateral cerebellar cortex. Many of the glial cells that were immunostained with heat shock protein of 27kDa co-localized with cells immunoreactive for glial fibrillary acidic protein. After severe injury, heat shock protein of 72kDa was localized mainly in granule cells at the site of the trauma and in the ipsilateral deep cerebellar nuclei whereas, after mild injury, light labeling was observed only in the granule cell layer. The results demonstrate that focal cerebellar injury has profound effects on motor behavior and induces different families of heat shock proteins in specific groups of neurons and glial cells in the cerebellum.