Restorative Neurology and Neuroscience - Volume 3, issue 5

Authors: Boyeson, Michael G. | Feeney, Dennis M.

Article Type: Research Article

Abstract: The following experiment was designed to examine the effects of unilateral cerebellar cortex lesions and pharmacological postinjury treatments with catecholamine drugs on recovery of beam walking ability in rats. Rats trained on a beam walking task were initially given either amphetamine, haloperidol, or a combination of the drugs at 24 h after injury, and tested at various intervals after drug administration. Six total doses were given to animals at 5d intervals during recovery. All drugs retarded recovery of function on the beam walking task compared to saline controls. Animals with cortical lesions that involved the deep cerebellar nuclei showed no …recovery on the beam, regardless of group assignment. Phenoxybenzamine and propranalol were both ineffective in reinstating the beam walking deficit in those animals that demonstrated recovery on the beam walking task. The results indicate that the cerebellum plays a particularly important role in recovery of beam walking ability, and may contribute to beam walking recovery commonly observed after sensorimotor cortex ablations. Show more

Keywords: Catecholamine, Cerebellum, Diaschisis, Brain injury, Amphetamine

DOI: 10.3233/RNN-1991-3501

Citation: Restorative Neurology and Neuroscience, vol. 3, no. 5, pp. 227-233, 1991

Authors: Lau, Kam Cheung | So, Kwok-Fai | Cho, Eric Yu Pang

Article Type: Research Article

Abstract: The morphology of the retinal ganglion cells (RGCs) with their axons regenerating along a peripheral nerve graft at different post-grafting periods was studied by the intracellular injection of Lucifer yellow (LY) and silver staining methods. Several morphological features which were observed on developing RGCs, but not mature RGCs, have also been observed in the regenerating RGCs studied by the intracellular injection of LY. These morphological features observed on the regenerating RGCs included intraretinal axonal branches and collaterals, spine-like processes on the dendrites and soma, and short processes on the soma. These results suggest that damaged mammalian RGCs may be able …to recapitulate certain cellular events which occur during normal development provided the regenerating cells are given the proper stimulus and a favorable environment for regrowth. From the results of both LY injection and silver staining experiments, it was found that the dendrites of the regenerating RGCs were, in general, much simpler than that of control Type I RGCs. However, regenerating RGCs with different degree of dendritic complexity could be observed in all post-grafting periods studied, and the dendritic complexity seems to decrease continuously with the increase in the post-grafting time. These results suggest that the ability to regenerate an axon is not closely related to dendritic responses and the peripheral nerve does not seem to be able to prevent the deterioration and retraction of the dendrites. Show more

Keywords: Retinal ganglion cell, Peripheral nerve graft, Lucifer Yellow, Silver staining

DOI: 10.3233/RNN-1991-3502

Citation: Restorative Neurology and Neuroscience, vol. 3, no. 5, pp. 235-246, 1991

Authors: Clark, Robert E. | Delay, Eugene R.

Article Type: Research Article

Abstract: Two experiments examined the effects of postoperative auditory intensity training on serial brightness reversal learning of visual decorticate rats. In Experiment 1 rats learned an avoidance response cued by a high intensity light prior to visual decortication. Six days later the rats were given either avoidance training with an auditory intensity cue, additional training with the preoperative visual cue, or no training. The next day all rats began a series of 8 brightness discrimination reversals. The no-training lesion group failed the early reversals but reached criterion in later reversals. Lesion rats retrained with visual cues failed early reversals with the …low intensity light cue but not reversals with the high intensity cue. In contrast, lesion rats given auditory training easily reached criterion in all reversals. Experiment 2 followed a similar training sequence except auditory training was given after the second reversal. All rats showed rapid acquisition of all visual reversals subsequent to auditory training. These data suggest that generalization of a learning set by cross-modal transfer training with an intact modality can reduce reversal learning deficits following brain damage more efficiently than comparable training with the damaged system. Show more

Keywords: Reversal learning, Cross-modal transfer, Visual cortex lesion, Rat, Visual discrimination, Auditory discrimination

DOI: 10.3233/RNN-1991-3503

Citation: Restorative Neurology and Neuroscience, vol. 3, no. 5, pp. 247-255, 1991

Authors: Hao, J.-X. | Xu, X.-J. | Aldskogius, H. | Seiger, Å. | Wiesenfeld-Hallin, Z.

Article Type: Research Article

Abstract: In this study we examined the effect of the long-acting opioid antagonist naltrexone on the allodynia-like effect of spinal ischemia in rats. The spinal cord ischemia was induced at midthoracic level by a recently developed photochemical technique using laser irradiation and photoactivatable intravascular dyes. An allodynia-like sensory disturbance, where the animals reacted by vocalization to non-noxious mechanical stimuli in the flank area, was consistently seen during several days after ischemia. Pretreatment with 10 and 20 mg/kg, but not 5 mg/kg naltrexone i.v. 10 min before irradiation decreased the incidence of allodynia. However, even the effect of the highest dose of …naltrexone (20 mg/kg) was incomplete, which is in contrast to the effect of the NMDA receptor antagonist MK-801, which has been tested in the same model and found to completely prevent the incidence of allodynia at a dose of 0.5 mg/kg. Pretreatment with sub- or suprathreshold doses of naltrexone (5 and 20 mg/kg respectively) combined with a subthreshold dose of MK-801 (0.1 mg/kg) did not produce a synergistic effect. When naltrexone (20 mg/kg) was administered 10 min after induction of ischemia, it was totally ineffective in decreasing the occurrence and severity of allodynia. In contrast, MK-801 (0.5 mg/kg) still had a good protective effect when injected as this time. Histological examination showed slight morphological damage in the spinal cord in 38% of control rats after 1 min laser irradiation without pretreatment with naltrexone. No morphological abnormalities were observed in rats after pretreatment with naltrexone (20 mg/kg). The results suggest that opioid receptor antagonists and NMDA receptor antagonists prevent a consequence of transient spinal cord ischemia through different mechanisms. High doses of opioid antagonists may have anti-ischemic effects by improving local spinal cord microcirculation and therefore may have a role in preventing ischemia after traumatic spinal cord injury. On the other hand, the NMDA receptor may have a role in the secondary neuronal death resulting from ischemia. Thus, NMDA receptor antagonists may contribute to the prevention of tissue damage by antagonizing the excitotoxic action of glutamate and/or aspartate released by ischemia into the spinal cord. Finally, since only high doses of naltrexone had an effect in the present study, we cannot rule out the possiblity that this drug may act through non-opioid mechanisms. Show more

Keywords: Allodynia, Ischemia, MK-801, Naltrexone, NMDA receptor, Opioid receptor, Rat, Spinal cord

DOI: 10.3233/RNN-1991-3504

Citation: Restorative Neurology and Neuroscience, vol. 3, no. 5, pp. 257-266, 1991

Authors: Brailowsky, S. | Montiel, T. | Hernández-Echeagaray, E. | Flores-Hernández, J. | HernáNdez-Pineda, R.

Article Type: Research Article

Abstract: To screen drugs potentially useful in the pharmacological treatment of subjects with brain lesions, we studied the effects of chronic (7 and 30 days) treatments with a Ginkgo biloba extract (EGb761-IPSEN; EGb) in two animal models of cortical hemiplegia: one induced by motor cortex aspiration and another using a reversible inactivation of the motor cortex through chronic, localized infusion of y-aminobutyric acid (GABA), via osmotic minipumps. The elevated beam test was used in water-deprived animals trained to drink saccharin-sweetened solutions (with or without EGb) and to perform to criteria before the surgical procedures. From the day after surgery, the rats …were administered 100 mg/kg of EGb daily for 7 or 30 days. In all groups with motor impairment in which the extract was administered, a faster and more complete recovery was observed, which was significantly different from that of rats which received only saccharin solutions. The salutary effect of EGb was more marked in ablation-induced hemiplegia than in the GABA-treated group. In the former injury model, EGb-treated animals had smaller ventricular diameters than non-treated rats. No differences concerning sensory deficits were detected among groups. EGb was also acutely administered during the epileptic syndrome that follows interruption of chronic GABA infusions (the GABA-withdrawal syndrome). No anticonvulsant effects of EGb were observed. These results suggest a potential use of EGb in brain-injured patients as this product shows little toxicity in animals and man after chronic administration. The active principles among terpenes (ginkgolides, bilobalides and flavonolheterosides present in the EGb) and the mechanisms for this beneficial effects remain to be elucidated. Show more

Keywords: Motor cortex, GABA, Beam test, Plasticity, Recovery, Brain injury, Epilepsy

DOI: 10.3233/RNN-1991-3505

Citation: Restorative Neurology and Neuroscience, vol. 3, no. 5, pp. 267-274, 1991

Article Type: Research Article

DOI: 10.3233/RNN-1991-3506

Citation: Restorative Neurology and Neuroscience, vol. 3, no. 5, pp. 275-281, 1991