ABSTRACT
Constraint-induced movement therapy (CIMT), which involves restraint of the nonimpaired arm coupled with physiotherapy for the impaired arm, lessens impairment and disability in stroke patients. Surprisingly, immediate ipsilateral forelimb immobilization exacerbates brain injury in rats. We tested whether immediate ipsilateral restraint for 7 days aggravates injury after a devascularization lesion in rats. Furthermore, we hypothesized that ipsilateral restraint aggravates injury by causing hyperthermia. In experiment 1, each rat received two lesions, one in the motor cortex and one in the visual cortex. Ipsilateral restraint increased only the motor cortex lesion. In additional rats, no differences in core temperature occurred after ipsilateral or contralateral restraint. Thus, ipsilateral restraint does not aggravate injury by a systemic side effect. In experiment 2, we hypothesized that ipsilateral restraint causes hyperthermia in the region surrounding the initial cortical lesion. Brain temperature, measured via telemetry, was significantly higher (approximately 1 degrees C for 24 h) with ipsilateral restraint. A third experiment similarly found that ipsilateral restraint aggravates injury and causes local cortical hyperthermia and that contralateral restraint with externally induced mild hyperthermia aggravates injury. In conclusion, immediate ipsilateral restraint aggravates injury apparently by localized events that include hyperthermia. Caution must be exercised in applying early CIMT to humans, as hyperthermia is detrimental.
Subject(s)
Fever/etiology , Motion Therapy, Continuous Passive/methods , Motor Cortex/injuries , Motor Cortex/physiopathology , Restraint, Physical/methods , Animals , Body Temperature , Canada , Disease Models, Animal , Forelimb , Functional Laterality , Immobilization , Male , Motion Therapy, Continuous Passive/adverse effects , Motor Cortex/blood supply , Movement/physiology , Physical Therapy Modalities , Rats , Rats, Long-Evans , Rats, Wistar , Restraint, Physical/adverse effects , Stroke/pathology , Stroke/physiopathology , Stroke/therapy , Time FactorsABSTRACT
The formalin test was developed using an ordinal scale of weighted scores to rate the intensity of pain-related behaviours in animals. However, no studies have been carried out to establish the ordinal relationship of the behavioural categories used to generate the weighted pain intensity scores. The purpose of the present study was to evaluate the validity of the weighted-scores technique by assessing the ordinality of the behavioural categories associated with the specific category weights. The amount of time spent in each of 4 behavioural categories was measured as a function of the concentration of the formalin solution injected into the hindpaw of rats, and as a function of the dose of systemic morphine given to rats injected with a concentrated (5.0%) solution of formalin. The ordinal nature of the category weights was supported when the data were subjected to a polychotomous logistic regression for fitting an ordinal model.
Subject(s)
Behavior, Animal/drug effects , Formaldehyde/pharmacology , Pain Measurement/drug effects , Animals , Male , Models, Biological , Morphine/pharmacology , Rats , Regression AnalysisABSTRACT
The local anesthetic lidocaine was injected into the dentate gyrus (DG) of alert, unrestrained rats 10 min prior to investigation within the formalin test. Regional anesthesia of the DG resulted in a reduction of pain scores when administered contralateral to the site of subcutaneous formalin injection. The analgesic effect was evident 30-50 min after central infusion. These results provide evidence of the involvement of the hippocampal formation (HF) in pain perception.
