Hemiparkinsonism in monkeys after unilateral internal carotid artery infusion of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)

Infusion of MPTP (0.2-0.8 mg/kg) into the right internal carotid artery of monkeys produces toxin-induced injury to the right nigrostriatal pathway with sparing of other dopaminergic neurones on the infused side and with negligible or little injury to the opposite, untreated side. There are contralateral limb dystonic postures, rigidity, and bradykinesia, but the animals are able to eat and maintain health without drug treatment. Spontaneous motor activity is attended by circling towards the injured side, whereas treatment with L-DOPA/-carbidopa or apomorphine stimulates circling towards the intact side. Dopamine and dopamine metabolite levels are normal in the left caudate and putamen, but markedly depressed on the right (MPTP-treated) side. This animal hemiparkinsonian model will be useful in studies of volitional movement control, drug treatments of Parkinson's disease, and functional efficacy of brain tissue implants.     

Intracarotid 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine Administration: Biochemical and Behavioral Observations in a Primate Model of Hemiparkinsonism

Cynomolgus monkeys received intracarotid injections of the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to produce a chronic unilateral model of parkinsonism. Extensive dopamine (DA) depletion was observed in the caudate nucleus and putamen on the side ipsilateral to the injection and this was associated with contralateral tremor, rigidity, and bradykinesia. A dose of 1.25 mg of MPTP caused ipsilateral DA loss of 99.4% in the caudate nucleus, 99.8% in the putamen, and 74.2% in the nucleus accumbens. A dose of 2.5 mg caused ipsilateral DA depletion of 99.3% in the caudate nucleus, 99.5% in putamen, and 90.1% in the nucleus accumbens. The unilateral aspect of the lesion was dose sensitive, with the 2.5-mg dose causing bilateral asymmetric DA depletion. Tissue concentrations of serotonin were not affected by the toxin. These findings confirm that intracarotid injection of MPTP may produce a useful primate model of hemiparkinsonism that can be associated with selective unilateral DA depletion when the appropriate dose of toxin is used.     

单侧帕金森病猴模型的行为、神经递质、多巴胺受体、病理及局部脑血流研究

经右侧颈总动脉注射甲基-苯基-四氢吡啶(MPTP)使猴产生左侧肢体动作减少、行动迟缓、震颤及向右侧缓慢旋转。应用美多巴和阿朴吗啡显著地改善单侧帕金森病(PD)症状,同时引起向左侧快速旋转,并呈明显的剂量依赖性;应用苯丙胺引起向右侧快速旋转。连续应用美多巴诱致单侧PD猴产生舞蹈手足徐动症。高效液相色谱测定显示右侧壳核、尾状核和黑质多巴胺(DA)含量显著降低。光镜发现右侧黑质神经元变性。SPECT活体显像发现病损侧纹状体D_2DA受体活性在病损初期无改变,病损严重时超敏,以及病损侧脑血流灌注减低。实验表明MPTP可建成理想的能形象地模拟人类PD的单侧PD猴模型。SPECT是活体研究PD病理生理的有效检测手段。     

Sequential rearrangements of ensemble activity of the putamen neurons of monkeys as a correlate to continuous behavior

Simultaneous recording of unit activity of 6-8 putamen neurons in two monkeys (M. nemestrina and M. mulatta) during performance of the task of alternative spatial choice, was carried out. The extent of rearrangements of the activity in the groups of neurons with the transition from every step of the behavioral program to the next one and the degree of difference in mosaics of reactivity, forming at every step with a different variants of performance, were evaluated using discriminative analysis. The rearrangements of the impulse activity were recorded in all steps of the program. The dynamics of rearrangements with the choice of right or left feeder was different, which resulted in appearance of significant differences in mosaics of reactivity at the stage of decision making and receiving reward. The rearrangements preceding the task-oriented movement of one hand were more pronounced in the contralateral hemisphere. The volume of rearrangements may increase with the performance of movement but the differences of mosaics formed during the movement of right and left hand are decreasing. At the stage of reception of the reward, the rearrangements were greater in case the animal chose the certain (left) feeder irrespective of the side of recording the unit activity.     

Differentiating activity of monkey putamen neurons during performance of the alternative spatial choice

Single unit activity was recorded in monkeys in three putamen zones learned a bimanual operant activity during performance of the task of alternative spatial choice. The neuronal reactions were specially analyzed by the criteria as follows: a) differentiation of the side of reward (differentiating--non-differentiating reactions); b) character of reaction by duration (tonic-phasic); c) laterality (contra- and ipsilateral reactions as related to hemisphere); d) frequency of background activity. It was shown that differentiating cell activity, especially their tonic part and in still greater degree contra-lateral tonic reactions most closely correlate with behavioral aspects of the program. The assumption that differentiating activity, unlike non-differentiating one, is the reflection of not only morphological and neurochemical characteristic features of nervous elements of putamen but of its functional uniformity in relation to external determinants of behavior, was put forward.     

Precentral neuron activity associated with ipsilateral forelimb movements in monkeys.

Unit activity was recorded in motor cortex on one side, while monkeys were moving left or right fingers, wrists, or arms. On hundred and eighty five movement-related neurons were obtained from two monkeys. Of these, 122 were related to contralateral movements, 50 were to movements of both sides, and the remaining 13 to ipsilateral movements. It was found that ipsilateral-movement-related neurons tended to appear in groups of neurons that were related more to arm movements than to finger and/or wrist movements.     

Performing Permanent Distal Middle Cerebral with Common Carotid Artery Occlusion in Aged Rats to Study Cortical Ischemia with Sustained Disability

Stroke typically occurs in elderly people with a range of comorbidities including carotid (or other arterial) atherosclerosis, high blood pressure, obesity and diabetes. Accordingly, when evaluating therapies for stroke in animals, it is important to select a model with excellent face validity. Ischemic stroke accounts for 80% of all strokes, and the majority of these occur in the territory of the middle cerebral artery (MCA), often inducing infarcts that affect the sensorimotor cortex, causing persistent plegia or paresis on the contralateral side of the body. We demonstrate in this video a method for producing ischemic stroke in elderly rats, which causes sustained sensorimotor disability and substantial cortical infarcts. Specifically, we induce permanent distal middle cerebral artery occlusion (MCAO) in elderly female rats by using diathermy forceps to occlude a short segment of this artery. The carotid artery on the ipsilateral side to the lesion was then permanently occluded and the contralateral carotid artery was transiently occluded for 60 min. We measure the infarct size using structural T2-weighted magnetic resonance imaging (MRI) at 24 hr and 8 weeks after stroke. In this study, the mean infarct volume was 4.5% ± 2.0% (standard deviation) of the ipsilateral hemisphere at 24 hr (corrected for brain swelling using Gerriet’s equation, n = 5). This model is feasible and clinically relevant as it permits the induction of sustained sensorimotor deficits, which is important for the elucidation of pathophysiological mechanisms and novel treatments.     

Neural Activity in the Macaque Putamen Associated with Saccades and Behavioral Outcome

It is now widely accepted that the basal ganglia nuclei form segregated, parallel loops with neocortical areas. The prevalent view is that the putamen is part of the motor loop, which receives inputs from sensorimotor areas, whereas the caudate, which receives inputs from frontal cortical eye fields and projects via the substantia nigra pars reticulata to the superior colliculus, belongs to the oculomotor loop. Tracer studies in monkeys and functional neuroimaging studies in human subjects, however, also suggest a potential role for the putamen in oculomotor control. To investigate the role of the putamen in saccadic eye movements, we recorded single neuron activity in the caudal putamen of two rhesus monkeys while they alternated between short blocks of pro- and anti-saccades. In each trial, the instruction cue was provided after the onset of the peripheral stimulus, thus the monkeys could either generate an immediate response to the stimulus based on the internal representation of the rule from the previous trial, or alternatively, could await the visual rule-instruction cue to guide their saccadic response. We found that a subset of putamen neurons showed saccade-related activity, that the preparatory mode (internally- versus externally-cued) influenced the expression of task-selectivity in roughly one third of the task-modulated neurons, and further that a large proportion of neurons encoded the outcome of the saccade. These results suggest that the caudal putamen may be part of the neural network for goal-directed saccades, wherein the monitoring of saccadic eye movements, context and performance feedback may be processed together to ensure optimal behavioural performance and outcomes are achieved during ongoing behaviour.     

Physical activity is linked to ceruloplasmin in the striatum of intact but not MPTP-treated primates

Ceruloplasmin is a protective ferroxidase. Although some studies suggest that plasma ceruloplasmin levels are raised by exercise, the impact of exercise on brain ceruloplasmin is unknown. We have examined whether striatal ceruloplasmin is raised with treadmill exercise and/or is correlated with spontaneous physical activity in rhesus monkeys. Parkinson??s disease is characterized by a loss in ceruloplasmin and, similarly, Parkinson??s models lead to a loss in antioxidant defenses. Exercise might protect against Parkinson??s disease and is known to prevent antioxidant loss in experimental models. We have therefore examined whether treadmill exercise prevents ceruloplasmin loss in monkeys treated unilaterally with the dopaminergic neurotoxin MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine). We found that exercise raised ceruloplasmin expression in the caudate and accumbens but not the putamen of intact monkeys. However, putamen ceruloplasmin was correlated with spontaneous activity in a home pen. MPTP alone did not cause unilateral loss of ceruloplasmin but blocked the impact of exercise on ceruloplasmin. Similarly, the correlation between putamen ceruloplasmin and activity was also lost with MPTP. MPTP elicited loss of tyrosine hydroxylase in the treated hemisphere; the remaining tyrosine hydroxylase was correlated with overall daily activity (spontaneous activity plus that induced by the treadmill). Thus, treadmill activity can raise ceruloplasmin but this impact and the link with spontaneous activity are both diminished in Parkinsonian primates. Furthermore, low overall physical activity predicts greater loss of dopaminergic phenotype in MPTP-treated primates. These data have implications for the maintenance of active lifestyles in both healthy and neurodegenerative conditions.     

Comparison of nonenzymatic glycosylation of arterial and venous collagens

The extent of nonenzymatic glycosylation of collagen isolated from sheep carotid arteries and jugular veins was compared. It was found that the level of this modification in the arterial collagen was about 2.7 times higher than that in the venous collagen. Arteriovenous fistulae were established between the common carotid artery and external jugular vein on one side only of six sheep. Sham arteriotomy and phlebotomy were performed on the contralateral vessels. Although there was an increase in the concentration of these ketoamine-linked hexoses in all the tissue samples assayed, a difference of between two- and three-fold was maintained between the arterial and venous tissue. The relationship of this finding to the development of vascular complications and to the level of circulating reducing sugar is discussed.     

Influence of cerebral ischemia and post-ischemic reperfusion on mitochondrial oxidative phosphorylation

Unilateral ischemia in the right cerebral hemisphere of the rat was induced by ligation of the right common carotid artery coupled with controlled hemorrhage to produce hypotension (25±8 mm/Hg). Where indicated after 30 min of ischemia, the withdrawn blood was reinfused to restore arterial pressure to normal. Mitochondria isolated from the ipsilateral hemisphere after 30 min of ischemia showed significantly lower respiratory rates than the organelles isolated from the contralateral side. Oxidation of NAD⁺-linked substrates was more sensitive to inhibition in ischemia (30%) than was of ferrocytochromec (12%), succinate oxidation being intermediate. The activities of membrane-bound dehydrogenases (both NADH and succinate-linked) were also significantly lowered. Ischemia did not affect the cytochrome content of mitochondria. Respiratory activity (NAD⁺-linked) of mitochondria isolated from the ipsilateral hemisphere was twice as sensitive to inhibition by fatty acid as was of preparations from the contralateral side. Mitochondria isolated from cerebral cortex after 90 min of post-ischemic reperfusion showed no significant improvement in the rate of substrate oxidation. Adenine nucleotide translocase activity and energy-dependent Ca²⁺ uptake, both of which decreased significantly in mitochondria isolated from the ischemic brain, showed little recovery, on reperfusion. These observations suggested the strong possibility that the deleterious effects of ischemia on mitochondrial respiratory function might be mediated by free fatty acids that are known to accumulate in large amounts in ischemic tissues. The pattern of inhibition of ATPase activity was consistent with this view.     

Effect of baroreceptor activity on ventilatory response to chemoreceptor stimulation.

This study tested the hypothesis that ventilatory responses to chemoreceptor stimulation are affected by the level of arterial pressure and degree of baroreceptor activation. Carotid chemoreceptors were stimulated by injection of nicotine into the common carotid artery of anesthetized dogs. Arterial pressure was reduced by bleeding the animals and raised by transient occlusion of the abdominal aorta. The results indicate that ventilatory responses to chemoreceptor stimulation were augmented by hypotension and depressed by hypertension. In additional studies we excluded the possibility that the findings were produced by a direct effect of changes in arterial pressure on chemoreceptors. Both carotid bifurcations were perfused at constant flow. In one carotid bifurcation, perfusion pressure was raised to stimulate carotid sinus baroreceptors. In the other carotid bifurcation, pressure was constant and nicotine was injected to stimulate carotid chemoreceptors. Stimulation of baroreceptors on one side attenuated the ventilatory response to stimulation of contralateral chemoreceptors. This inhibition was observed before and after bilateral cervical vagotomy. We conclude that there is a major central interaction between baroreceptor and chemoreceptor reflexes so that changes in baroreceptor activity modulate ventilatory responses to chemoreceptor stimulation.     

Behavioral recovery associated with central nervous system regeneration in the snail Melampus

The pulmonate snail Melampus bidentatus regenerates central nervous tracts following commissurotomy, connective transection, and cerebral ganglion ablation. Our goal was to determine whether or not neural regrowth within the central nervous system restored behaviors disrupted by lesions. One behavior that is disrupted by commissurotomy is retraction of facial structures that are contralateral to a stimulated facial region, a response that normally accompanies the ipsilateral retraction. Tentacle withdrawal on the side contralateral to stimulation reappeared on a timescale that was correlated with growth of a commissural link (8-19 days post-lesion). Electrophysiological recordings from a labial nerve pathway that has a contralateral component similar to the contralateral tentacle response showed that development or strengthening of an alternative pathway could also mediate contralateral responses. Thus, a major conclusion of this study was that both tract regeneration and changes in existing CNS pathways can underlie recovery. The percentage (approx. 75%) of snails that regenerate the cerebral commissure and show behavioral recovery is established early in the period following commissure transection. Behavioral recovery and anatomical evidence of regeneration were also correlated in the other two operations: single cerebral ganglion removal and unilateral cerebropleural and cerebropedal connective transection. We conclude that Melampus is able to regenerate neuronal connectivity that can restore normal behavior.     

A functional and structural investigation of the human fronto-basal volitional saccade network

Almost all cortical areas are connected to the subcortical basal ganglia (BG) through parallel recurrent inhibitory and excitatory loops, exerting volitional control over automatic behavior. As this model is largely based on non-human primate research, we used high resolution functional MRI and diffusion tensor imaging (DTI) to investigate the functional and structural organization of the human (pre)frontal cortico-basal network controlling eye movements. Participants performed saccades in darkness, pro- and antisaccades and observed stimuli during fixation. We observed several bilateral functional subdivisions along the precentral sulcus around the human frontal eye fields (FEF): a medial and lateral zone activating for saccades in darkness, a more fronto-medial zone preferentially active for ipsilateral antisaccades, and a large anterior strip along the precentral sulcus activating for visual stimulus presentation during fixation. The supplementary eye fields (SEF) were identified along the medial wall containing all aforementioned functions. In the striatum, the BG area receiving almost all cortical input, all saccade related activation was observed in the putamen, previously considered a skeletomotor striatal subdivision. Activation elicited by the cue instructing pro or antisaccade trials was clearest in the medial FEF and right putamen. DTI fiber tracking revealed that the subdivisions of the human FEF complex are mainly connected to the putamen, in agreement with the fMRI findings. The present findings demonstrate that the human FEF has functional subdivisions somewhat comparable to non-human primates. However, the connections to and activation in the human striatum preferentially involve the putamen, not the caudate nucleus as is reported for monkeys. This could imply that fronto-striatal projections for the oculomotor system are fundamentally different between humans and monkeys. Alternatively, there could be a bias in published reports of monkey studies favoring the caudate nucleus over the putamen in the search for oculomotor functions.     

Choline Acetyltransferase Activity in the Rat Brain Cortex Homogenate, Synaptosomes, and Capillaries After Lesioning the Nucleus Basalis Magnocellularis

Stereotaxic lesions of the nucleus basalis magnocellularis were made unilaterally in male Wistar rats with either kainic or ibotenic acid, using the contralateral side as control. Differences in behavior, body weight, and survival were observed between the kainic and ibotenic acid-treated rats. One week after surgery, the rats were sacrificed and the effect of the lesions on choline acetyltransferase activity was measured in brain cortex homogenate, synaptosomes, and capillaries. In kainic acid-lesioned rats, choline acetyltransferase activity decreased in homogenate and synaptosomes of the ipsilateral side with respect to that of the contralateral side; but the ibotenic acid lesion, which also reduced the ipsilateral choline acetyltransferase activity in homogenate, showed a rather different effect on the enzymatic activity of the synaptosomes. There were also differences between the effect of kainic and ibotenic acid lesions on choline acetyltransferase activity in the capillaries of the ipsilateral side with respect to that of the contralateral one. However, capillary choline acetyltransferase activity of the treated rats was in both sides three times higher than that of unoperated rats.     

In Vivo Electrochemical Studies of Dopamine Overflow and Clearance in the Striatum of Normal and MPTP-Treated Rhesus Monkeys

Abstract: Rapid chronoamperometric recordings, using Nafion-coated carbon-fiber electrodes (30–90 µm o.d.), were used to investigate overflow and uptake of dopamine (DA) in the striatum of normal and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated rhesus monkeys. The monkeys were anesthetized with isoflurane and placed in a stereotaxic apparatus. Magnetic resonance imaging-guided sterile stereotaxic procedures were used for implantations of the electrochemical electrodes coupled with single-barrel micropipettes that were used to apply potassium or DA locally. Potassium evoked a robust overflow of DA-like electrochemical signals into the brain extracellular space in the unlesioned or normal putamen and caudate nucleus of the rhesus monkeys. In contrast, potassium did not produce any detectable changes (> 97% depletion) of DA in the MPTP-lesioned striatum. In addition, the diffusion/clearance of locally applied DA was markedly altered in the lesioned caudate nucleus and putamen compared with unlesioned striatum. Cell counts of the number of residual tyrosine hydroxylase-positive neurons in MPTP-treated monkeys, in conjunction with whole-tissue levels of DA and its metabolites, showed that the MPTP lesions produced extensive damage of the nigrostriatal DA system. These data indicate that residual dopaminergic fibers remaining after MPTP lesions are dysfunctional and have a greatly diminished capacity for high-affinity DA uptake.     

Lower cranial nerve motor function in unilateral vascular lesions of the cerebral hemisphere.

Motor function subserved by cranial nerves V, VII, X, XI, and XII was assessed in 100 patients with hemiparesis due to a unilateral vascular lesion of the cerebral hemisphere. Several of the findings were not described clearly in many of the standard textbooks of neurology. Weakness of sternomastoid when present was always contralateral to the hemiparesis. This emphasises the principle that the cerebral hemisphere controls movement of the body parts in or towards the contralateral half of the body rather than simply the contralateral muscle groups. An apparent exception to this was seen, however, in the small group of patients who had unilateral weakness of the tongue. In those patients deviation of the tongue was towards the hemiparetic side--that is, the cerebral hemisphere controlled the contralateral half of the tongue and hence protrusion towards the ipsilateral side. Mild dysarthria was common with both right and left sided hemiparesis.     

Restoration of contralateral representation in the mouse somatosensory cortex after crossing nerve transfer

Avulsion of spinal nerve roots in the brachial plexus (BP) can be repaired by crossing nerve transfer via a nerve graft to connect injured nerve ends to the BP contralateral to the lesioned side. Sensory recovery in these patients suggests that the contralateral primary somatosensory cortex (S1) is activated by afferent inputs that bypassed to the contralateral BP. To confirm this hypothesis, the present study visualized cortical activity after crossing nerve transfer in mice through the use of transcranial flavoprotein fluorescence imaging. In naïve mice, vibratory stimuli applied to the forepaw elicited localized fluorescence responses in the S1 contralateral to the stimulated side, with almost no activity in the ipsilateral S1. Four weeks after crossing nerve transfer, forepaw stimulation in the injured and repaired side resulted in cortical responses only in the S1 ipsilateral to the stimulated side. At eight weeks after crossing nerve transfer, forepaw stimulation resulted in S1 cortical responses of both hemispheres. These cortical responses were abolished by cutting the nerve graft used for repair. Exposure of the ipsilateral S1 to blue laser light suppressed cortical responses in the ipsilateral S1, as well as in the contralateral S1, suggesting that ipsilateral responses propagated to the contralateral S1 via cortico-cortical pathways. Direct high-frequency stimulation of the ipsilateral S1 in combination with forepaw stimulation acutely induced S1 bilateral cortical representation of the forepaw area in naïve mice. Cortical responses in the contralateral S1 after crossing nerve transfer were reduced in cortex-restricted heterotypic GluN1 (NMDAR1) knockout mice. Functional bilateral cortical representation was not clearly observed in genetically manipulated mice with impaired cortico-cortical pathways between S1 of both hemispheres. Taken together, these findings strongly suggest that activity-dependent potentiation of cortico-cortical pathways has a critical role for sensory recovery in patients after crossing nerve transfer.     

Experimental analysis of temporomandibular joint reaction force in macaques

Mandibular bone strain in the region immediately below the temporomandibular ligament was analyzed in adult and sub-adult Macaca fascicularis and Macaca mulatta. Following recovery from the general anesthetic, the monkeys were presented food objects, a wooden rod, or a specially designed bite-force transducer. Bone strain was recorded during incisal biting and mastication of food, and also during isometric biting of the rod and/or the transducer. The bone strain data suggest the following: The macaque TMJ is loaded by a compressive reaction force during the power stroke of mastication and incision of food, and during isometric molar and incisor biting. TMJ reaction forces are larger on the contralateral side during both mastication and isometric molar biting. Patterns of ipsilateral TMJ reaction force in macaques during isometric biting vary markedly in response to the position of the bite point. During biting along the premolars or first two molars a compressive reaction force acts about the ipsilateral TMJ; however, when the bite point is positioned along the M3, the ipsilateral TMJ has either very little compressive stress, no stress, or it is loaded in tension.     

MK-801 Prevents 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine-Induced Parkinsonism in Primates

In cynomologus monkeys, systemic administration of MK-801, a noncompetitive antagonist for the N-methyl-D-aspartate receptor, prevented the development of the parkinsonian syndrome induced by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). MK-801 also attenuated dopamine depletion in the caudate and putamen and protected dopaminergic neurons in the substantia nigra from the degeneration induced by the neurotoxin. Nevertheless, 7 days after MPTP administration in the caudate and putamen of monkeys also receiving MK-801, the levels of toxic 1-methyl-4-phenylpyridinium were even higher than those measured in monkeys receiving MPTP alone. This indicates that the protective action of MK-801 is not related to MPTP metabolism and strongly suggests that, in primates, the excitatory amino acids could play a crucial role in the mechanism of the selective neuronal death induced by MPTP.