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The brainstem reticular formation, subthalamus and thalamus were explored in a search for units modulated by the respiratory centre. Experiments were performed on cats under local anesthesia, in which respiratory center oscillation was independent of movement of the lungs and thorax. A large proportion of units firing tonically showed an increasing frequency, phase related to phrenic nerve activity. Respiration related units (RRUs) rostral to the pneumotaxic centre were concentrated in definite areas of the brainstem reticular formation, subthalamus and thalamus. Respiratory modulation disappeared rostral to a section performed at the ponto-mesencephalic junction.
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The histochemical distribution of some aminotransferases at various levels through the midbrain and cerebrum and in the peripheral nervous system of the rat has been described. The selective localization of the reaction product in the neurons and the neuropil was the same for the aminotransferases studied. There was a difference in the intensity of the enzyme activity. The white matter was negative, and only the glial cells and the blood vessels exhibit transaminase activity. Some nuclei showed an intensive reaction in the neurons and neuropil: nuel. ruber, substantia nigra, hypothalamic nuclei, Ammon's horn. A high activity was observed in the ganglion cell, and the nerve fibres were negative. There was a great similarity between the pattern of distribution for aminotransferases and that for some dehydrogenases.
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Action potentials evoked in a phase-locked 1 : 1 relationship by natural electric organ discharges (EOD) were recorded extracellularly and intracellularly from single mesencephalic magnocellular nucleus units in the high frequency electric fish Sternarchus albifrons (Gymnotidae). This activity has been shown to be the result of an extrinsic feedback of the electrosensory system and is probably important for the socalled jamming avoidance response triggered artificial electric pulses when delivered into the water in a 1 : 1 relationship at intensities higher than the EOD. In the same way, artificial pulses of frequency near EOD could either drive or, due to beats, greatly disturb the regular firing of the units. More insight into the neural mechanism was yielded by single EOD-triggered shocks provoking a failure in firing of certain action potentials of the series and causing long-lasting (10-20 ms) accelerations and decelerations of the regular EOD-evoked firing (transient disturbance). Intracellular stimulations show similar effects. The biological significance of this neural mechanism for the fish's electroperception and JAR is discussed.
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The fresh volume of the Nucl. interpeduncularis of 52 white mice aged between 17 and 60 days of ontogenesis has been determined. The data have been fitted by the logistic function and the ideal volume (0.32 mm3) the half value time (21.6 days of ontogenesis) and the factor of enlargement (2.65) have been derived. The Nucl. interpeduncularis is one of the early and fast growing brain regions. The growth parameters of this nucleus have been discussed and have been compared with the parameters of other cortical and subcortical limbic brain regions.
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The proliferation and directions of cell differentiation in tectum opticum were studied in the young frogs under the conditions of normal development and upon brain trauma by means of 3H-thymidine autoradiography. The same types of cells were shown to be able of proliferation in both the cases: cells of the ventricle zone and glioblasts (gliocytes) in all other tectum layers. A study of directions of the tectum proliferating cells' differentiation in the frogs has shown that the proliferating cells differentiate mainly in the ependyme tanicytes in the ventricle layer 1 and gliocytes in the other tectum layers. The trauma did not change the direction of proliferating cells' differentiation towards the formation of neurons. The complete regeneration is observed in the tectum layer 1 only.
The fresh volumes of the Nucl. medialis and of the Nucl. lateralis corporis mammillaris of 52 white mice aged between 17 and 60 days of ontogenesis have been determined. The fresh volume of the left Nucl. lateralis is significantly larger than that of the right side. The data of the Nucl. laterales have been fitted by a 3parametric logistic function. The data of the Nucl. medialis have been fitted by a sum of logistic functions. This sum has an increasing and a decreasing component and it shows a maximum of the sum of both components near 32 days of ontogenesis. The degree of maturity and the growth-rate of maturity have been discussed. Both nuclei belong to the group of brain regions in white mice with an early development. The growth of different brain regions is asynchronous. There is a need for further quantitative analyses.
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The fresh volumes of the Nucl. mediales et laterales habenulae of 52 male white mice aged between 17 and 60 days of ontogenesis have been determined. The data of both nuclei have been fitted by a sum of logistic functions. There is an increasing component and a decreasing component. The degree of maturity and its differential quotient have been discussed. The Nucl. medialis habenulae belongs to those structures of the central nervous system developing extremely early, the Nucl. lateralis habenulae belongs to those structures of the central nervous system developing extremely early, the Nucl. lateralis habenulae belongs to those structures developing early. It has been pointed out, that there is a complex heterochrony of regional development in the brain. There have to be more quantitative analyses.
A single dose of corticosterone (1 mg/kg b.w.i.p.) increased the 5-hydroxytryptamine (5-HT) content in the mesencephalon, amygdala and hypothalamus. The maximum was observed at 15 min following administration. The 5-HT level returned to normal between 60 and 180 min. The 5-hydroxyindoleacetic acid (5-HIAA) content decreased in the mesencephalon and hypothalamus at 15 min, and then increased to the maximum at 30 min in the mesencephalon and at 45 min in the hypothalamus and amygdala. There were no changes in the septum and hippocampus either in 5-HT or in 5-HIAA content following corticosterone administration. Desoxycorticosterone administration (1 mg/rat i.p.) was ineffective. Tritiated 5-HT uptake did not change in the hypothalamus and mesencephalon tissue in vitro after corticosterone or desoxycorticosterone treatment. Adrenalectomy caused a decrease in the 5-HT content in all brain areas studies. 5-HIAA decreased only in the hypothalamus. Corticosterone administration normalized the 5-HT and 5-HIAA content in the hypothalamus and mesencephalon in adrenalectomized rats. Tritiated 5-HT uptake was lower in the hypothalamus and mesencephalon in adrenalectomized rats. Corticosterone administration increased the activity back to normal in the hypothalamus, however desoxycorticosterone was ineffective. The data suggest that the plasma corticosterone level plays a role in the regulation of the activity of the serotoninergic system in certain limbic brain structures.