Assessment of recovery in the hemiparkinson rat: Drug-induced rotation is inadequate

Recovery from apomorphine-induced rotational behavior was compared to sensorimotor and motor function in hemiparkinsonian rats receiving intrastriatal grafts of astrocytes expressing recombinant tyrosine hydroxylase (TH) or control β-galactosidase (β-gal). Rats received unilateral intranigral infusions of 6-hydroxydopamine (6-OHDA). Animals with large lesions, as determined by apomorphine-induced rotation, received grafts of astrocytes into the denervated striatum. Behavioral recovery was assessed on days 14-16 post-transplantation using apomorphine-induced rotation, somatosensory neglect, and reaching for pellets using the Montoya staircase method. Rats that received transplants of TH-transfected astrocytes showed a 34% decrease in rotational behavior, but no consistent recovery of somatosensory neglect or skilled reaching. Post-mortem histological analyses revealed survival of grafted astrocytes in host striatum and expression of TH at 17 days post-transplantation. We suggest that TH-expressing astrocytes may reverse post-synaptic dopamine (DA) receptor supersensitivity; however, sensorimotor and motor abilities are not restored due to a failure by TH-expressing astrocytes to reestablish dopaminergic circuitry. The present results demonstrate the need to utilize a variety of sensory and motor behavioral tests that cohesively provide greater interpretability than a single behavioral measure used in isolation, such as drug-induced rotational behavior, to assess the efficacy of experimental gene therapies.