Is experimental catalepsy properly measured?

Regional specific effects of clozapine and haloperidol on GABA and dopamine release in rat basal ganglia

gamma-Aminobutyric acid (GABA) and dopamine release were measured concomitantly in rat dorsolateral striatum, fundus striati (a ventral region of striatum) and globus pallidus following s.c. administration of haloperidol or clozapine. Release was measured by microdialysis in halothane-anesthetized rats. Clozapine (5.0 mg/kg) increased GABA release in the fundus striati and haloperidol (0.5 mg/kg) increased GABA release in the globus pallidus. In contrast, clozapine (2.5-40 mg/kg) failed to increase GABA release in the globus pallidus and haloperidol (0.1-2.0 mg/kg) failed to increase GABA release in the fundus. Thus, haloperidol and clozapine are clearly distinguished by their effects on GABA release in the fundus striati and globus pallidus (both drugs increased GABA release in the dorsolateral striatum). Dopamine release was increased by haloperidol and clozapine in the two regions of the striatum. However, except in the fundus striati where clozapine-induced increases in dopamine and GABA occurred in parallel, both drugs were more potent in releasing dopamine than GABA. Drug-induced increases in GABA and dopamine release were reversed by addition of 1 microM tetrodotoxin to the perfusion medium. These data suggest that (1) regional differences in the effects of haloperidol and clozapine on GABA release in the basal ganglia may parallel the unique clinical profiles of these drugs; and (2) increases in dopamine release may occur independently of a GABAergic component in the dorsolateral striatum following low doses of haloperidol and clozapine and in the fundus striati following all effective doses of haloperidol.

Neural grafts and pharmacological intervention in a model of Huntington's disease

Using the excitotoxic animal model of Huntington's disease, two experimental treatments were evaluated. The first experiment explored the effect of MK801 (a systemically active anticonvulsant, and noncompetitive NMDA antagonist) pretreatment on quinolinic acid (QA)-induced striatal degeneration and behavioral deficits. MK801 prevented QA-induced neuropathological changes in the striatum and the anatomical protection was correlated with the absence of deficits in the cataleptic response to haloperidol. The second experiment tested the ability of three types of fetal grafts to reverse behavioral deficits induced by kainic acid (KA) lesion. Fetal (E15-16) striatal, cortical and tectal grafts were delivered into the KA-lesioned striatum one week or one month after lesion. Animals in this experiment were evaluated on a motor coordination task, haloperidol-induced catalepsy and amphetamine-induced locomotor activity. Striatal grafts attenuated the deficits induced by KA in all of the tasks observed, and no effect of time of grafting was detected. Tectal grafts had a partial beneficial effect, attenuating the decrease in the cataleptic response to haloperidol observed after KA lesions. No effect of time of grafting was detected for these grafts. In contrast, a clear effect of time of grafting was detected for the cortical grafts. Early cortical grafts reversed the exaggerated response to amphetamine observed after KA lesions whereas late cortical grafts resulted in sham-like scores on the catalepsy test. Histochemical analysis showed that most of the grafts survived, had acetylcholinesterase (AChE) positive fibers and cell bodies, and were metabolically active as indicated by cytochrome oxidase (CO) positive staining. It is suggested that striatal grafts may have restored to some extent the striatal GABAergic control over output structures, and that trophic factors play a role in behavioral recovery as is evident from the beneficial effects of the tectal grafts. Although the mechanisms underlying the differential effects observed after early or late cortical grafts are unknown, the interaction between the cellular components and trophic factors present in the cortical grafts and the condition of the lesioned host at the time of grafting may yield a host-graft complex with a unique profile.