Models of neurological defects and defects in neurological models

Experimental focal ischemic injury: behavior-brain interactions and issues of animal handling and housing

In experimental neurological models of brain injury, behavioral manipulations before and after the insult can have a major impact on molecular, anatomical, and functional outcome. Investigators using animals for preclinical research should keep in mind that people with brain injury have lived in, and will continue to live in, an environment that is far more complex than that of the typical laboratory rodent. To yield more reliable and relevant behavioral assessment, it may be appropriate in some cases to house animals in environments that allow for motor enrichment and to handle animals in ways that promote tameness. Experience can affect mechanisms of plasticity and degeneration beneficially or adversely. Behavioral interventions that have been found to modulate postinjury brain events are reviewed. The timing and interaction of biological and motor therapies and the potential contribution of experience-dependent and drug-induced trophic factor expression are discussed.

Pharmacological validation of behavioural measures of akinesia and dyskinesia in a rat model of Parkinson's disease

In an attempt to define clinically relevant models of akinesia and dyskinesia in 6-hydroxydopamine (6-OHDA)-lesioned rats, we have examined the effects of drugs with high (L-DOPA) vs. low (bromocriptine) dyskinesiogenic potential in Parkinson's disease on three types of motor performance, namely: (i) abnormal involuntary movements (AIMs) (ii) rotational behaviour, and (iii) spontaneous forelimb use (cylinder test). Rats with unilateral 6-OHDA lesions received single daily i.p. injections of L-DOPA or bromocriptine at therapeutic doses. During 3 weeks of treatment, L-DOPA but not bromocriptine induced increasingly severe AIMs affecting the limb, trunk and orofacial region. Rotational behaviour was induced to a much higher extent by bromocriptine than L-DOPA. In the cylinder test, the two drugs initially improved the performance of the parkinsonian limb to a similar extent. However, L-DOPA-treated animals showed declining levels of performance in this test because the drug-induced AIMs interfered with physiological limb use, and gradually replaced all normal motor activities. L-DOPA-induced axial, limb and orolingual AIM scores were significantly reduced by the acute administration of compounds that have antidyskinetic efficacy in parkinsonian patients and/or nonhuman primates (-91%, yohimbine 10 mg/kg; -19%, naloxone 4-8 mg/kg; -37%, 5-methoxy 5-N,N-dimethyl-tryptamine 2 mg/kg; -30%, clozapine 8 mg/kg; -50%, amantadine 40 mg/kg). L-DOPA-induced rotation was, however, not affected. The present results demonstrate that 6-OHDA-lesioned rats do exhibit motor deficits that share essential functional similarities with parkinsonian akinesia or dyskinesia. Such deficits can be quantified using novel and relatively simple testing procedures, whereas rotometry cannot discriminate between dyskinetic and antiakinetic effects of antiparkinsonian treatments.

Akinesia and postural abnormality after unilateral dopamine depletion

Following unilateral nigrostriatal dopamine depletion rats engage in drug-induced and spontaneous turning. These asymmetric behaviors are associated with a hemispheric asymmetry in the dopamine function. Several tests of 'spontaneous' behavior have revealed other abnormalities, primarily in posture and akinesia. A test is described here which quantifies postural abnormalities, as well as difficulties in initiating and terminating movement. This test may be suitable for evaluating aspects of dopamine-mediated behaviors not addressed by drug tests and may prove valuable in evaluating the potential of new treatment strategies for Parkinson's disease.

Validation of a rodent model of Parkinson's Disease: evidence of a therapeutic window for oral Sinemet

Behavioral measures of parkinsonism that are more clinically relevant than rotometry have been developed for rats with severe unilateral dopamine depletions, and the validity of these measures is supported by reports that these parkinsonian symptoms are attenuated by drugs that are effective in the clinical setting. Although the therapeutic gold standard, L-DOPA:carbidopa (Sinemet), effectively attenuates parkinsonian symptoms, the beneficial effects of this drug are limited by the dyskinesias that it produces at higher doses. The range of effective doses, from the minimum dose that produces beneficial effects to the dose that produces intolerable dyskinesias, is referred to as the "therapeutic window." It would be extremely valuable to assess, preclinically, the effects of novel treatments on the therapeutic window for Sinemet. The results of the present study support the validity of nondrug-induced measures of parkinsonian symptoms in dopamine-depleted rats. Neurological measures revealed large behavioral deficits in the affected forelimb analogous to the deficits exhibited in Parkinson's disease patients, and these deficits were significantly attenuated with some doses of oral Sinemet (30-40 mg/kg). These drug effects on measures of parkinsonism were specific to performance with the affected limb. At slightly higher doses (50 mg/ kg), the rats were untestable due to severe dyskinesias. The results of the present study suggest that it is possible to investigate the therapeutic potential of novel treatments as well as their effects on the therapeutic window of oral Sinemet in this rodent model of Parkinson's disease.