Amphetamine, haloperidol, and experience interact to affect rate of recovery after motor cortex injury

Activation, arousal, and neuropsychological rehabilitation

This paper addresses the concept of arousal and the role of the reticular system in producing the orienting response. For patients with deviant autonomic responses, the use of central neuropharmacological stimulants is considered. Their therapeutic value is discussed in relation to hyperactive children and individual adult cases of the posttraumatic syndrome consequent upon traffic accidents.

Cerebral decortication reverses the effect of amphetamine on striatal D2 dopamine binding site density

Unilateral ablation of the cerebral cortex produces a decrease of approximately 38% in striatal D2 dopamine binding site density. Chronic d-amphetamine treatment also produces a decrease of about 22% in D2 binding site density. Paradoxically, when rats were hemidecorticated and treated chronically with d-amphetamine, the density of striatal D2 dopamine binding sites on the decorticated side was increased (by about 50%) rather than decreased. Evidently d-amphetamine-induced down-regulation of D2 dopamine binding sites depends on an intact corticostriatal pathway.

Exposure to amphetamine after substantia nigra lesion interferes with the process of behavioral recovery

Recovery from unilateral substantia nigra lesion may be indicated by re-emergence of circling in the pre-lesion preferred direction. Following 6-OHDA-induced lesion of the dominant SN, we examined: (a) The effect of the delay from lesioning on amphetamine-induced rotation asymmetry, and (b) The effect of early post-lesion exposure to amphetamine on later rotation asymmetry. d-Amphetamine was initially injected either 7, 14, 21, or 30 days after lesioning. Transient circling in pre-lesion preferred direction (contralateral to lesioned side) was more frequently encountered on days 7 and 30 after lesioning, as compared to days 14 and 21. The contralateral rotation observed on day 7 is attributed to degeneration-induced DA release, whereas contralateral rotation noted on day 30 is believed to reflect the operation of post-lesion compensatory processes within the spared DA neurons. In response to subsequent amphetamine administration 30 days after lesioning, rats with previous exposure to the drug circled ipsilaterally, whereas most rats given amphetamine for the first time in that session rotated contralaterally to the lesion. These findings suggest that post-lesion administration of amphetamine interferes with the process of recovery.

Correlation between behavioral status and cerebral glucose utilization in rats following freezing lesion

Standard small, superficial freezing lesions placed along the anterior-posterior plane of the left cortex produced behavioral changes in rats. One to 3 days following the lesion, rats showed asymmetries in somatosensory responsiveness, decreases in running wheel activity and difficulty with limb coordination. No changes in spontaneous circling were seen. At the completion of the behavioral testing on day 3 the [14C]2-deoxyglucose method confirmed the presence of widespread depression in local cerebral glucose utilization with cortical areas ipsilateral to the lesion being most affected. At this time the degree of the somatosensory deficit was significantly correlated with the extent of the depression of glucose utilization in the cortical areas of the lesioned hemisphere. At 6 days following the lesion only deficits in limb coordination remained, while local cerebral glucose utilization had returned to within normal limits. It is concluded that the demonstrated behavioral changes were a manifestation of widespread functional depression, as reflected by decreased cortical glucose utilization throughout the lesioned hemisphere.

Effects of neonatal forebrain noradrenaline depletion on recovery from brain damage: performance on a spatial navigation task as a function of age of surgery and postsurgical housing

The experiments examined the contributions of forebrain noradrenaline and environmental enrichment to recovery of place navigation ability in rats after hemidecortication in infancy or adulthood. Noradrenaline depletion did not affect recovery from neonatal hemidecortication, although the early hemidecortications did allow sparing of function relative to adult operates. Noradrenaline depletion also failed to attenuate the positive effects of enriched housing on otherwise normal rats. Noradrenaline depletion did retard recovery of adult hemidecorticate rats housed in standard laboratory cages, but it did not retard recovery of adult hemidecorticate rats housed in enriched environments. The results suggest that noradrenaline is importantly involved in enhancing recovery from brain damage when other sources of compensation (e.g., neonatal injury, enriched environment) are absent.

Recovery of function after brain damage: severe and chronic disruption by diazepam

Following unilateral damage to the anterior-medial region of the neocortex (AMC) in rats a sensory asymmetry appeared, but recovered within a week. In a separate group of rats with AMC lesions daily 3-week exposure to diazepam (Valium, 5 mg/kg) beginning 12 h after surgery caused recovery to be delayed indefinitely. The efficiency and speed (as opposed to symmetry) of behavior was not impaired. More than 9 weeks after discontinuation of diazepam (12 weeks postsurgery), recovery was still not apparent. Postmortem analysis ruled out lesion size as a contributing factor. In a second experiment undrugged animals with AMC lesions were allowed to recover for at least 3 weeks before being exposed to diazepam. These animals showed only a transient (2-day) reinstatement of asymmetry despite continuous drug treatment. We conclude that important mechanisms serving recovery of function may be vulnerable during a short period soon after brain damage.

gamma-Aminobutyric acid-induced potentiation of cortical hemiplegia

A novel model of hemiplegia in young and aged rats is described. Osmotic minipumps were used to deliver a chronic (7 days), localized application of gamma-aminobutyric acid (GABA) (100 micrograms/microliter/h), to the somatomotor cortex of unrestrained rats. This resulted in an easily quantifiable, contralateral and reversible motor syndrome in both young and aged animals. In the young group, the motor deficit cleared over 5-day period, while in the aged animals it persisted for at least a 2-week period. Control animals treated with saline-filled minipumps did not develop a long-lasting motor deficit. The GABA-induced facilitation of hemiplegia due to small motor cortex lesions and the age effects on behavioral recovery of function are discussed. Cortical inhibitory mechanisms may play a role in debilitating syndromes such as stroke or post-epileptic paralysis.

Reinstatement of binocular depth perception by amphetamine and visual experience after visual cortex ablation

In adult cats with bilateral visual cortex ablation the complete deficit in binocular depth perception, as measured on a visual cliff, was reversed by 4 doses of amphetamine. The amphetamine-induced recovery endured after the amphetamine treatment was discontinued. This enduring recovery of function was not obtained if the animals were housed in the dark during drug intoxication. Therefore, both amphetamine intoxication and visual experience are simultaneously required for recovery of binocular depth perception after visual cortex ablation.

Striatal dopamine after cortical injury

After right or left unilateral sensorimotor cortex ablation or a sham operation, dopamine concentrations were assayed in the right and left striatum of rats. In the sham-operated animals, a greater amount of dopamine was found in the left striatum compared with the right. Right or left sensorimotor cortex injury reduced dopamine in both striata. Right hemisphere lesions produced a greater loss of dopamine in the right striatum compared with the effect of a left lesion on dopamine in the left striatum. The results support the hypothesis of an asymmetric response to cortical injury.

Reversible motor paralysis in rats after repeated electroconvulsive shock

Repeated electroconvulsive shocks (ECS) delivered at brief (10 to 15 min) intervals through earclip electrodes, induced a reversible motor paralysis in 35% of treated rats. Paralysis was characterized by loss of locomotor activity without apparent loss of sensory functions. It occurred after 10 to 13 shocks regardless of whether stimulation was of subthreshold (40 to 60 mA) or suprathreshold (65 mA) intensity. This phenomenon may provide a useful animal model for the investigation of reversible injury to the spinal cord.

Amphetamine with experience promotes recovery of locomotor function after unilateral frontal cortex injury in the cat

In cats, a single dose of D-amphetamine (AMP) given at 10 days after unilateral frontal cortex ablation produced an immediate and enduring (60 day) acceleration of beam-walking ability compared to saline control animals. Four doses of AMP at 4-day intervals promoted recovery faster than a single dose of AMP. Subjects with no beam-walking experience while under AMP intoxication were not different from saline controls after two doses of AMP. However, after 4 doses these cats recovered significantly faster than saline controls and were comparable to animals that received AMP and experience under the drug.

Can amnesia be caused by damage of a single brain structure?

The relation of amnesia and damage to some particular brain regions is discussed by reviewing the main findings of selected human case reports. It is argued that frequently a too straightforward and unidimensional interpretation of the relations between brain damage and a behavioral deficit is formulated in such reports. Evidence obtained by modern anatomical techniques as well as the widespread and time-dependent effects of lesions make it necessary to consider a lesion of a particular structure of the brain and correlated mnemonic disturbances as possibly due to an altered equilibrium in an extensive network of the brain. The primary lesion of one or the other specific structure may lead to severe and lasting amnesia or may fail to do so depending on its influence on other brain regions.

Amphetamine and apomorphine restore tactile placing after motor cortex injury in the cat

Unilateral motor cortex injury in the cat results in a prolonged loss of tactile placing in the forelimb contralateral to the injury. Amphetamine (5 mg/kg) temporarily reverses this tactile placing deficit as early as 4 days following the injury. Racemic amphetamine was found to produce a significantly more prolonged restoration of placing than the d isomer, which was significantly more effective than the l isomer. Haloperidol (0.4 mg/kg) blocked the amphetamine-induced recovery of placing responses and also blocked placing in nondrugged cats showing partial spontaneous recovery. This dosage of haloperidol had no effect on tactile placing in normal cats. Apomorphine at moderate dosages (0.25 and 0.5 mg/kg) produced a weak restoration of tactile placing in motor cortex-injured animals. These pharmacological data suggest that the loss of tactile placing after motor cortex injury is due to a depression of catecholaminergic function, which is temporarily reversible by catecholaminergic stimulation.