Biomedical subjects
Publications and source records attributed to R Hassler.
After unilateral enucleation in the tree shrew (Tupaia glis), axo-dendritic synapses degenerate within two secondary visual centers (intergeniculate and lateral pulvinar nuclei). Degenerated optic terminals were found in both pulvinar nuclei on the contralateral side much more often than on the ipsilateral one.
A combined Golgi/electron microscopic technique was used to investigate tne fine structure and synaptology of Golgi-stained spiny neurons in the caudate nucleus of the cat. In order to study the termination sites of cortical afferents on Golgi-stained spiny neurons, cortical fibres were caused to degenerate by making extensive cortical lesions 3 days prior to fixation of the animals. When examined in the electron microscope, perikarya of labelled spiny neurons have a round nucleus, a few mitochondria and microtubules, and a poorly developed Golgi apparatus and rough endoplasmic reticulum. Only rarely are axo-somatic contacts seen. Labelled dendrites exhibit a moderate number of microtubules and sometimes elongated mitochondria. Numerous labelled spines are seen in the vicinity of their parent dendrites. They are contacted by smaller type I and type III boutons and larger type IV boutons (Hassler et al. 1978). Large boutons filled with clear round vesicles establish symmetric contacts with labelled dendritic shafts. Degenerating boutons of cortical afferents are seen in contact with spines and, more rarely, with dendritic shafts of Golgi-stained spiny neurons. All degenerating boutons synapsing with labelled structures are found some distance from the cell body. No contacts of degenerating cortical boutons with the soma or with stem dendrites of Golgi-stained spiny neurons are found.
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In 2 patients with retrocollis, the positive effects obtained by stereotactic high frequency coagulation of the prestitial nucleus on the tonic activity of the neck muscle were studied electromyographically and clinically. Before the stereotactic therapy, electromyographic recordings at rest were recorded from the musculi splenii. During stimulation of the prestitial nucleus at frequencies of 8, 25 and 50 Hz, the EMG activity at rest diminished in frequency and amplitude and ultimately disappeared. Passage from the EMG recordings at rest to electrical silence took place, in one case, though a rhythmic activity of potentials grouped at 11/s. After coagulation of the prestitial nucleus, the involuntary contractions of neck muscles disappeared and electrical silence occurred. On reexamination 1 month later, the positive results were still present.
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Acetylcholine neurons in the striatum are believed to be primarily intrinsic. In cats a cylinder of caudate tissue was isolated unilaterally from all afferent and efferent connections while preserving the blood supply through the base of the cylinder. Cats were decapitated two and four weeks after operation. Dorsal, intermediate and ventral portions of the viable isolated cylinder, and corresponding tissue from the contralateral hemisphere serving as control, were removed, weighed and frozen. Deuterated internal standards at concentrations approximating those of acetylcholine and choline in the tissue were added and acetylcholine and choline extracted, reacted with propionyl chloride and demethylated with sodium benzenethiolate. The derivatives were separated by gas chromatography, and the acetylcholine and choline concentrations in the tissue evaluated using selected ion monitoring of m/z 58, 60 and 64. The observed decrease in the acetylcholine concentration in the dorsal portion could be due either to the interruption of the cholinergic thalamic input or to the more severe ischemia in this portion. The increase in the acetylcholine concentration in the ventral portion, where blood circulation is normal, may reflect accumulation of acetylcholine in inactive intrinsic neurons after severance of their input, or indicate sprouting of intrinsic acetylcholine neurons.
The degenerative changes within the cat's subthalamic nucleus (Sth) following lesions of the external pallidum were studied by electron microscopy. Four to five days following pallidal lesions a great number of terminals undergoing degenerative changes were encountered in the ipsilateral Sth. The contralateral Sth was free of degeneration. The degenerating terminals show predominantly the light degenerative type, less frequently the dark degenerative pattern, and occasionally exhibit signs of filamentous hyperplasia. The degenerated boutons usually insert on perikarya of the large Sth neurons, on proximal dendrites, and more rarely contact dendritic spines. They were observed neither to perform synaptic contacts with the perikarya of the small Sth neurons nor with other vesicle-containing profiles. On the basis of the ultrastructural aspect of the degenerating terminals, they were identified as F1 terminals, discriminated in a previous study (Romansky et al., 1978). The normal appearance, the synaptic relationships, and the degenerative features of the F1 terminials in the Sth closely resemble the entopeduncular terminals in the thalamus described by Rinvik and Grofová (1974a), and Grofová and Rinvik (1974). The possible contribution of the interrupted passing fibers to the observed degeneration is discussed. The present findings corroborate the relevant morphological, physiological, neurochemical, and neuropharmacological data in the literature.
Aspartate, glutamate and GABA levels were determined in afferent and efferent projection nuclei of the striatum after unilateral cylindric lesion in the head of the caudate nucleus in cats. Two and four weeks after operation, GABA content was significantly reduced in substantia nigra and pallidum ipsilateral to the lesion. Glutamate (GLU) level was decreased in substantia nigra and pallidum only 4 weeks after lesion, whereas aspartate content in substantia nigra decreased significantly already after 2 weeks. No changes in the contents of these amino acids were detected in the dorsal raphe nucleus, which receives a projection from the caudate, as well as in the center median nucleus, which projects to the striatum. These experiments using longer survival times substantiate the role of GABA in caudato-pallidal and caudatonigral projections. The possibility is discussed that aspartate (ASP) could function as transmitter of cortico-nigral fibers.
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Field potentials, extracellular unitary discharges and intracellular potentials evoked by intrastriatal stimulation were recorded from slices (thickness 200-400 micron) of rat neostriatum maintained in an artificial medium. The field potentials consisted of two negative waves appearing at latencies of 0.5-1.5 ms (N-1) and 2-4 ms (N-2). Extracellular unitary records showed two typed of discharges, one with short but constant latencies at threshold level stimulation and the other with longer and variable latencies. In intracellular recordings the late discharge was seen to arise from EPSPs. Based on the intra- and extracellular unitary records, N-1 was identified as the population spike of antidromically or directly activated unitary discharges and N-2 as that of orthodromically activated discharges. This interpretation was substantiated by the fact that the N-2 potential was blocked in a perfusion medium containing a lower Ca++ or a higher Mg++ concentration than the standard solution. Neither interruption of ascending neostriatal inputs nor decortication 14 days prior to recording altered the configuration of the locally evoked potentials or the probability of synaptically driven discharge occurrence. Thus by intrastriatal stimulation, neostriatal neurons are activated antidromically or directly and/or orthodromically through intrinsic excitatroy synapses. Since the intracellular recordings showed that neostriatal neurons can be well preserved, this preparation can be regarded as a useful tool for electrophysiological and neuropharmacological investigations on intrinsic excitatory processes in the neostriatum.
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In the cat caudate nucleus the same nine types of synapses are found as in putamen and fundus striati. The three parts of the striatum in the strict sense do not differ in the morphological differentiation of synapse types but only in their quantitative distribution. One-third of all synapses in the caudate nucleus are axo-spinous type IV synapses with a curved and divided asymmetric contact. This strongly suggests that the caudate nucleus interneuronal apparatus is dominated by centre-median input, in contrast to the putamen which is controlled by the cortico-striatal input to its internuncial cells and by its strong intrastriatal feedback mechanism. Extensive destruction of the convexity of the cortex and the medial cortex in one hemisphere results in dark degeneration of a large proportion of two of the nine types of caudate synapses: a) the axo-dendritic type VII synapses exciting the large spiny caudate neurons and b) the axo-spinous type III synapses making contact with the small spiny neurons of the interneuronal cell apparatus.
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