The biochemistry of dyskinesias

Drug-induced tardive dyskinesia

Drug-induced tardive dyskinesia, which occurs in the course of long-term administration of psychotropic drugs, especially neuroleptics, and persists for years even after drug removal, began to be reported in the late 1950s. Since then, more than 100 investigations on this subjects have been described. And it is estimated that 10 to 30 percent of long-term hospitalized psychiatric patients in Europe and North America exhibit tardive dyskinesia, whereas 5 to 20 percent of patients exhibit this syndrome in Japan. These findings suggest that the manifestation of tardive dyskinesia will become a serious problem in the investigation of psychotropic drug treatment. The author presents a review of the symptomatology, etiological factors, differential diagnosis, prognosis, and management of this syndrome. Results of the author's studies in the cross-national survey and on the reversibility of tardive dyskinesia are also described. In connection with biochemical theory of the etiology of tardive dyskinesia, a variety of therapeutic investigations have been carried out, but no successful therapy could be found among them. Therefore, the author stresses that the early diagnosis of dyskinetic symptoms, possible removal of responsible drugs, and preventive care in daily psychotropic drug treatment are regarded as extremely important in the management of this syndrome.

Mass spectrometric identification of Cu, Zn, Fe, Co, Mn, Mg, and Pb in mammalian brain

Combining the techniques of thin-layer chromatography (TLC) and mass spectrometry, we unambiguously identified the trace metals Cu, Zn, Fe, Pb, Mn, Co, and Mg in the brain of a female human who had no evidence of any pathologic disease in the central nervous system, and in brains from mouse, rat, guinea pig, and rabbit. These trace metals were also found in anatomic regions of human brain: cortex (gray), cortex (white), caudate nucleus, putamen, hippocampus, and thalamus, and in anatomic regions of rat brain: hypothalamus, cerebellum, stem striatum, and "the rest." The metals were characterized from the color and Rf values of their tetraphenylporphyrin chelates on TLC and from the mass and pattern of molecule ion cluster of the mass spectrum. The unexpected presence of lead in the brain is discussed.

The production of an alternative laboratory model of the Parkinson syndrome using a new benzylimidoylurea derivative LON 954

N-carbamoyl-2-(2,6-dichlorophenyl) acetamidine hydrochloride (LON 954) causes a reproducible rest tremor in mice, of rapid onset and short duration with no associated rigidity or akinesia and in the absence of any marked changes in body temperature or accompanying peripheral parasympathomimetic effects. This tremor can be antagonised by the dopamine receptor agonists L-Dopa, bromocriptine, nomifensine and piribedil, as well as by anticholinergic anti-Parkinson drugs having an inhibitory effect on dopamine uptake such as benapryzine and benztropine. In contrast, benzhexol, orphenadrine and amantadine had no effect. LON 954 appears to be more specific than oxotremorine for the detection of drugs having therapeutic potential in the treatment of Parkinson's disease, particularly those exerting their effect through dopaminergic systems. An antagonist (BS 100-141), which is a structural isomer of LON 954, is also described.

Binding of 14C-imipramine by pigmented and non-pigmented tissues

When pigmented and non-pigmented rabbit irides were incubated with various concentrations of 14C-imipramine at equilibrium (120 min), the accumulation of the drug by the pigmented iris was 1.5 times as great as that by the non-pigmented iris. The accumulated drug is lost from both types of irides in a complex fashion. However, even after 120 min of washing, the differences in accumulation remain nearly constant. When accumulation of the drug in the non-pigmented iris was analyzed by discontinuous sucrose density gradient, it was observed that the drug was bound mainly by the low density sucrose fractions where the synaptosomes separate. On the contrary, in the pigmented iris approximately 70% of the drug was found in the melanin-containing fraction. The homogenate from the substantia nigra accumulated 1.5 times more than that from the human brain cortex. The affinity of the drug for bovine iris melanin granules and the synthetic L-dopa melanin was 9.9 X 10(5) M-1 and 3.8 X 10(3) M-1, respectively. On the rabbit iris sphincter muscles, imipramine was evaluated for antimuscarinic effects. The apparent dissociation constants, KB values, for the antagonist in the non-pigmented and pigmented iris were 1.7 X 10(-7) M and 3.8 X 10(-6) M, respectively. The low antimuscarinic activity in the pigmented iris is attributed to the loss of the drug to the pigment. On this basis, relevancy of the drug binding by pigmented tissues to the effects of this tricyclic drug is discussed.

Mobility gaps: a mechanism for band gaps in melanins

The semiconductor behavior of melanins is reviewed and compared with quantum mechanical models of conduction in amorphous solids. The available data are consistent with extensions of Mott's basic model for amorphous semiconductors, whereas they are inconsistent with crystalline semiconductor models. An investigation of the specific conduction mechanisms operative in melanins in terms of the amorphous model should reveal important aspects of the band structure.

Transitory procaine-induced Parkinsonism

A case of prolonged, though reversible procaine-induced Parkinsonism treated with l-dopa and trihexyphenidyl (Artane-Sustets) is reported. A pathophysiological explanation is discussed on the basis of recent theories concerning the transmitter systems of the basal ganglia.

Tremor induced by tetrabenazine

1. Acute administration of tetrabenazine produced tremor in cats, in doses which caused sedation but not hypothermia.2. The pattern of movements resembled shivering rather than Parkinsonism, and warming the skin suppressed the tremor.3. The tremor was not influenced by hyoscine.4. Tremor produced by amylobarbitone was essentially similar to that induced by tetrabenazine.

Effect of tetrabenazine on extrapyramidal movement disorders

Thirty patients with various extrapyramidal movement disorders were treated for prolonged periods with 75 to 225 mg. daily of tetrabenazine. In patients with choreiform and hemiballistic motor activity the involuntary movements were diminished or abolished. In patients with cerebellar or Parkinsonian tremor the tremor was aggravated in moderately severe cases, but was uninfluenced in severe cases. In all cases the dyskinesia returned when- the drug was stopped.Side-effects were inconsiderable and disappeared on reducing the dose slightly. Hence the drug may be an important alternative to neurosurgical treatment of hyperkinesias and especially suitable for severely disabled patients.