Decreased mu-opioid receptor binding in the globus pallidus of rats treated with chronic haloperidol.

RATIONALE: Chronic neuroleptic treatment produces a movement disorder in rats characterized by vacuous chewing movements (VCMs). Neuroleptics also produce a variety of changes in opioid neurotransmission in several regions of the basal ganglia. Rats with the VCM syndrome show elevated mRNA for enkephalin in striatopallidal neurons, suggesting a possible role for enkephalin in the pathophysiology of VCMs. OBJECTIVE: This study investigated the role of mu-opioid receptor density in the basal ganglia on the expression of VCMs. METHODS: Rats were treated with haloperidol for 24 weeks and withdrawn for 9 weeks. Mu (m) receptors were labeled with [3H]-DAMGO. RESULTS: Haloperidol treatment produced a significant reduction in mu-receptor binding in the globus pallidus (P<0.05). There was, however, no relationship between mu-opioid receptor density and VCMs in this or any other region of the basal ganglia. CONCLUSION: These results replicate prior findings of a neuroleptic-induced reduction in [3H]-DAMGO binding in the globus pallidus. The lack of association between VCMs and [3H]-DAMGO binding in the globus pallidus or any other region suggests that prior reports of enkephalinergic mRNA changes in the striatum are not accompanied by compensatory changes in postsynaptic neurons.

Generation of a mouse with low galactocerebrosidase activity by gene targeting: a new model of globoid cell leukodystrophy (Krabbe disease).

Globoid cell leukodystrophy (Krabbe disease) is a severe leukodystrophy caused by mutations in the galactocerebrosidase (GALC) gene leading to extremely low (less than 5% of normal activity) GALC activity. Human patients include primarily severely affected infants as well as patients with a later onset of symptoms. The infants usually die before 2 years of age, but it is difficult to predict the clinical course in older patients. In addition to these patients, additional individuals identified in this laboratory have 10--20% of normal GALC activity measured in accessible tissues. These individuals have a wide range of clinical presentations involving neurological degeneration. On molecular analysis of the GALC gene they all have three or more mutations considered to be normal polymorphisms resulting in amino acid changes in the two copies of the GALC gene. In order to investigate the role these amino acid changes may play on clinical, biochemical, and pathological findings, a new transgenic mouse was generated by homologous recombination. After preliminary studies determined what effect each amino acid change had on mouse GALC activity in transient transfection experiments, mice containing a cysteine residue at codon 168 instead of histidine (H168C) were produced. These mice developed symptoms, but they were delayed by 10--15 days from the well-characterized twitcher (twi) mouse. They accumulated psychosine slightly slower than twi mice, showed pathological changes less severe than twi mice in the central and peripheral nervous systems, and live about 15 days longer than twi mice. They have large litters and will play a role in therapy trials using new procedures currently under development.