Inability of flunarizine, lidoflazine or magnesium to counteract delayed hypoperfusion after forebrain ischaemia in the rat

Expressional changes in cerebrovascular receptors after experimental transient forebrain ischemia

BACKGROUND

Global ischemic stroke is one of the most prominent consequences of cardiac arrest, since the diminished blood flow to the brain results in cell damage and sometimes permanently impaired neurological function. The post-arrest period is often characterised by cerebral hypoperfusion due to subacute hemodynamic disturbances, the pathophysiology of which are poorly understood. In two other types of stroke, focal ischemic stroke and subarachnoid hemorrhage, it has earlier been demonstrated that the expression of certain vasoconstrictor receptors is increased in cerebral arteries several days after the insult, a phenomenon that leads to increased contraction of cerebral arteries, reduced perfusion of the affected area and worsened ischemic damage. Based on these findings, the aim of the present study was to investigate if transient global cerebral ischemia is associated with upregulation of vasoconstrictive endothelin and 5-hydroxytryptamine receptors in cerebral arteries. Experimental transient forebrain ischemia of varying durations was induced in male wistar rats, followed by reperfusion for 48 hours. Neurological function was assessed daily by three different tests and cerebrovascular expression and contractile function of endothelin and 5-hydroxytryptamine receptors were evaluated by wire myography, immunohistochemistry and western blotting.

RESULTS

Transient forebrain ischemia induced neurological deficits as well as functional upregulation of vasoconstrictive ET(B) and 5-HT(1B) receptors in cerebral arteries supplying mid- and forebrain regions. No receptor upregulation was seen in arteries supplying the hindbrain. Immunohistochemical stainings and western blotting demonstrated expressional upregulation of these receptor subtypes in the mid- and forebrain arteries and confirmed that the receptors were located in the smooth muscle layer of the cerebral arteries.

CONCLUSIONS

This study reveals a new pathophysiological aspect of global ischemic stroke, namely expressional upregulation of vasoconstrictor receptors in cerebral arteries two days after the insult, which might contribute to cerebral hypoperfusion and delayed neuronal damage after cardiac arrest.

Brain-injured persons in an altered state of consciousness: measures and intervention strategies

We evaluated the states of consciousness of seven persons who had sustained a severe head injury, and describe the behavioural manifestations associated with four treatment strategies. The subjects were between the ages of 19 and 55 and were recruited from both acute and long-term care facilities; all were in an altered state of consciousness. The severity of the injury was measured by time in coma, the scores on the Glasgow Coma Scale [1] and the Coma Near Coma Scale [2]. Structured interventions consisted of visual, auditory, olfactory, gustatory and tactile stimulation; behaviour was measured using the Disability Rating Scale [3, 4] and a portion of the Levels of Cognitive Functioning Scale [5]. Sensory-motor indications were recorded using a questionnaire developed by Freeman [6] and a quality-of-life instrument, developed for use with individuals having multiple disabilities [7], was adapted for the purpose of this study. Our results suggest that the use of structured interventions in the first 24 months following severe head injury is associated with a trend towards improved auditory and visual skills performance, manual performance, swallowing and language. Whereas initially no subject had any form of verbalization, by the final evaluation five subjects had some form of communication, either verbal or non-verbal.