Noradrenergic pharmacotherapy, intracerebral infusion and adrenal transplantation promote functional recovery after cortical damage

Abstract

The research described in this review briefly summarizes evidence that short term pharmacological enhancement of noradrenergic (NA) synaptic activity, combined with symptom relevant experience (SRE), promotes functional recovery of some symptoms of cortical damage in rat, cat and human beings even when treatment is initiated from days to weeks after injury. A summary is provided of the numerous drugs tested in rodent cortical injury models which have been proven useful for predicting beneficial or harmful effects on behavioral outcome in human stroke. The pattern of drug effects indicates a central role for NA in functional recovery. Additionally, studies of the effects of direct intraventricular infusion of monoamine neurotransmitters are reviewed and further support the hypothesized role of NA in recovery from some symptoms of cortical injury. The site of NA/SRE interaction to promote recovery from hemiplegia apparently involves the cerebellar hemisphere contralateral to the cortical injury. Microinfusions of NA into the contra- but not ipsilateral cerebellar hemisphere dramatically enhance recovery. Furthermore, like its systemic action, microinfusion of the alpha 1-NA receptor antagonist, phenoxybenzamine, reinstates hemiplegia. A "permanent" symptom of motor cortex injury in the cat is the complete loss of tactile placing contralateral to the injury which does not spontaneously recover for as long as seven years after ablation. This postural reflex is temporarily restored for 8-12 hours following amphetamine administration. However, this permanently lost reflex can be enduringly restored by transplanting catecholamine secreting adrenal tissue into the wound cavity. The experiment is reviewed in detail and involves chromaffin cell autografts into the frontal cortex ablation wound cavity producing a restoration of tactile placing for the 7-10 month duration of the study. This enduring restoration of tactile placing is considered a result of the release of catecholamines into the CNS from the grafted chromaffin cells found, by histochemical methods, surviving 7-10 months after transplant. Lastly, we attribute these delayed treatment effects to an attenuation of a diaschisis, or remote functional depression, in morphologically intact areas anatomically connected to the area of injury. The widespread reduction of glycolytic and oxidative metabolism, produced by focal cortical injury, is normalized by the same treatment which alleviates symptoms and is worsened by drugs which exacerbate deficits. These data support the hypothesis that providing SRE during a period of enhanced NA synaptic activity produces an enduring functional recovery after cortical injury by attenuating remote functional depression. This treatment for enhancing recovery is especially attractive since it is effective even when begun weeks after cortical damage.