[Tardive dyskinesia].
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Antipsychotic Agents↗
Biomedical subjects
A Ruffieux
Publications and source records attributed to A Ruffieux.
The somatotopy of the gracile nucleus in cats with agenesis of a hindfoot.
The somatotropic representation of the hindlimb in the gracile nucleus was studied in two cats who had a congenital defect of one hindfoot. The defect comprised all of the foot downward from and including the heel, and the distal third of tibia and fibula. The part of the sciatic nerve normally supplying the lower hindlimb and the hindfoot was reduced in diameter by one third. The motoneurones corresponding to the absent muscles were lacking and replaced by glial elements. The cross-sectional area of the dorsal columns at segment S2 was reduced by more than 20%. The gracile nuclei, in contrast, were not reduced in size. Only the diameter of its neurones was significantly smaller. Electrophysiological single and multi-neurone recordings revealed an altered somatotopic representation in the gracile nucleus on the defective side. The nuclear area normally representing the missing parts of the body surface now received input from the stump. There was no nuclear area devoid of afferent input, and there was no input in the gracile from the forelimb or from the contralateral side. It is concluded that the remaining parts of the leg project onto the gracile nucleus in an ordered fashion, sharing the entire nucleus according to their present afferent fibres.
Afferent Pathways↗
[Influence of dopamine on pars reticulata neurones of substantia nigra (author's transl)].
1 Dendrites of the dopamine neurones of pars compacta extend into pars reticulata of substantia nigra. The aim of the present study was to investigate whether dendritically released dopamine would be able to influence pars reticulata neurones. 2 In order to test this hypothesis, we have studied the effects of iontophoretically applied dopamine on pars reticulata neurones of substantia nigra in rats under chloralhydrate and under urethane anaesthesia. 3 The dopamine neurones of pars compacta and the neurones of pars reticulata were distinguished by their histological localization (Fig. 1 A) and their electrophysiological characteristics (Fig. 2). Sixty percent of reticulata neurones were antidromically excited from ipsilateral ventromedial thalamus (Fig. 4). 4 Both nigrothalamic and non-nigrothalamic neurones of pars reticulata were activated by iontophoretically applied dopamine, but never depressed (Fig. 5). This effect was blocked by iontophoretically applied fluphenazine. 5 The percentage of reticulata neurones excited by dopamine depended upon the anaesthetic agent: 39% when chloralhydrate, 8% when urethane was used (Table I). 6 As described before by others, dopamine neurones were depressed by dopamine (82%), but never excited (Fig. 6). This effect was also sensitive to fluphenazine. 7 The present results would support the concept that dendritically released dopamine not only affects other nigral dopamine neurones, but also influences non-dopaminergic nigral neurones, some of which project outside the basal ganglia.
Action Potentials↗
Dopaminergic activation of reticulata neurones in the substantia nigra.
Dendritic release of dopamine (DA) in substantia nigra (SN) is well established in various experimental situations. Morphological substrates for DA storage exist in dendrites, as do dendro-dendritic and dendro-axonic contacts. DA receptors in SN are located on both cells and striato-nigral terminals. DA is thought to regulate the activity of neighbouring dopaminergic neurones through its dendritic release by a local feedback mechanism. However, dendrites of DA neurones also ramify close to the neuropil of non-dopaminergic reticulata neurones in SN. The question has arisen whether dendritically release DA might also influence these neurones which, to a large extent, project to ventromedial thalamus (VM) and superior colliculus. A necessary condition would be that they are sensitive to DA. In the experiments reported here this was found to be the case--a considerable proportion of nigrothalamic neurones were activated by iontophoretically applied DA. This contrasts with its known depressant effect on pars compacta DA neurones which we confirmed.
Action Potentials↗