Diurnal variation in the concentrations of catecholamines and indoleamines in the median eminence and in the intermediate and posterior lobes of the pituitary gland of the male rat

Diurnal changes in monoamine concentrations were studied in the median eminence and in the intermediate and posterior lobes of the pituitary gland of the male rat. The concentrations of serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), noradrenaline (NA) and dopamine (DA) were analyzed at 7 time points over a 24-h period. Diurnal variation was analyzed by analysis of variance (ANOVA) with time of day as a class variable as well as by 24 h and 12 h cosine curve fittings. There were marked time-dependent changes in the median eminence concentrations of 5-HT (ANOVA: P = 0.0085), 5-HIAA (P = 0.003) and NA (P = 0.0003). Cosine curves with 24-h periods fit the data points with peaks around 13.00 h. DA levels also varied with an apparent 24-h rhythm in the median eminence, but the changes did not reach the level of significance in the ANOVA. In the intermediate lobe of the pituitary gland, the concentrations of DA varied significantly during the course of the 24-h cycle (P = 0.0011) and were well-fitted to a 24-h cosine wave. The 5-HIAA levels also showed marked diurnal changes (P = 0.025) with an evident 12-h rhythm. In contrast, NA and 5-HT concentrations did not appear to vary during the 24-h cycle. In the posterior lobe of the pituitary gland. DA had a 24-h rhythm (P = 0.0005) similar to the intermediate lobe. NA and indoleamine levels did not show any significant variation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Electrophysiology and analysis of the image of the development of Purkinje cells in culture and in the intact animal

The electrophysiological and morphological properties of the Purkinje cells (P cells) grown in organotypic cultures were studied in HRP intracellulary labelled neurons and compared to Golgi stained P cells from kitten of different ages. The effects of afferent fiber depletions on the final dendritic topological parameters were investigated by 3-dimensional reconstructions and computerized methods. In culture, the P cell dendritic trees always appeared reduced in size when compared to their in vivo counterparts. A discriminant analysis permitted the recognition of 3 populations of cultured P cells according to the type of deafferentation. In intact animals, the dendritic organization appeared biplanar around day 13. These results demonstrate that the presence of all normal inputs is required to achieve the full elaboration and the monoplanar disposition of the P cell dendrites.     

Fighting in the aged male mouse increases the expression of TrkA and TrkB in the subventricular zone and in the hippocampus

In the present study, we investigate the effect of aggressive behavior and release of nerve growth factor (NGF) on brain progenitor cells. We found that the condition of subordination enhances the level of NGF in the subventricular zone and hippocampus whereas dominance elevates brain derived neurotrophic factor (BDNF). It was also found that mRNA-TrkA is over-expressed in the subventricular zone and hippocampus of dominant and subordinate mice, whereas mRNA-TrkB is increased in the subventricular zone of both dominants and subordinates and in the hippocampus of dominant mice. Fighting was also associated with increased presence of proliferating cells in the hippocampus stained with the nuclear marker bromodeoxyuridine (BrdU). Moreover, the brain of subordinate mice displayed tyrosine hydroxylase (TH) immunoreactivity in the wall of the periventricular region of the third ventricles and a marked neuropeptide Y (NPY) presence in the hippocampus co-expressed with BrdU. These results provide additional evidence that agonistic behavior in the aged mouse alters neurotrophin levels and increases brain progenitor cells number. The functional significance of these findings is discussed.     

Imaging and modelling of digestion in the stomach and the duodenum

Gastroduodenal physiology is traditionally understood in terms of motor-secretory functions and their electrical, neural and hormonal controls. In contrast, the fluid-mechanical functions that retain and disperse particles, expose substrate to enzymes, or replenish the epithelial boundary with nutrients are little studied. Current ultrasound and magnetic resonance imaging allows to visualize processes critical to digestion like mixing, dilution, swelling, dispersion and elution. Methodological advances in fluid mechanics allow to numerically analyse the forces promoting digestion. Pressure and flow fields, the shear stresses dispersing particles or the effectiveness of bolus mixing can be computed using information on boundary movements and on the luminal contents. These technological advances promise many additional insights into the mechanical processes that promote digestion and absorption.     

Dopamine D3 modulation of locomotor activity and sleep in the nucleus accumbens and in lobules 9 and 10 of the cerebellum in the rat

Dopamine D3 receptors are present in the nucleus accumbens and in lobules 9 and 10 of the cerebellum. Their function is not fully understood. In the present study, the involvement of D3 receptors in locomotor activity and sleep in the two structures was investigated. The method used was the measure of locomotor activity in an open field and the measure of sleep and sleep/waking stages by electroencephalographic recordings in the rat. Dopamine receptor agonists (7-OH-DPAT, quinelorane and SKF38393) and antagonists (amisulpride, nafadotride and haloperidol) were microinjected into the two structures. Concerning locomotor activity, the results show that D3 receptor stimulation, as well as concomitant stimulation of D1 and D3 receptors, have opposite effects in the cerebellum and in the core of nucleus accumbens, with an inhibition of locomotion in the cerebellum and a stimulation of locomotion in the nucleus accumbens. D1 and D3 stimulation have mutual potentiating locomotor effects. The results also show that in the cerebellum, the effects are selective to lobules 9 and 10, and are not observed with microinjections into lobule 8. Concerning sleep, the effects of agonists and antagonists show a similar tendency in the cerebellum and nucleus accumbens, with a somnogenic effect of D2 blockage, an awakening effect of at least one of the D2/D3 agonists, and a dose-dependent awakening effect of the D2/D3 antagonists. In conclusion, this study suggests that dopamine D3 receptors in the cerebellum and nucleus accumbens are involved in several aspects of the regulation of locomotor activity and sleep.     

Noradrenaline concentration and turnover in nuclei of the hypothalamus and the medulla oblongata at two stages in the development of renal hypertension in the rat

The noradrenaline concentration and the α-methyl-para-tyrosine (α-MPT)-induced disappearance of noradrenaline were determined in several nuclei of the hypothalamus and the medulla oblongata of renal hypertensive rats (two-kidney Goldblatt hypertension). A decreased α-MPT-induced disappearance of noradrenaline was found in the nucleus interstitialis striae terminals and nucleus paraventricularis 3 days after renal artery constriction, when blood pressure was slightly, but significantly higher than that of sham operated rats. At this stage the α-MPT-induced disappearance of noradrenaline was enhanced in the nucleus commissuralis and the A₁ of hypertensive rats while the noradrenaline concentration in the A₁-region was significantly elevated. No significant differences were found in both parameters in hypothalamic and medullary nuclei 3.5 weeks after the operation, when hypertension had fully developed. These findings are indicative of the occurence of transient changes in the activity of noradrenergic neurons located in the medulla oblongata and projecting to the hypothalamus during the initiation of the development of two-kidney Goldblatt hypertension.     

Development of teaching and tuition in the specialty of neurology in the Netherlands

After a short survey of the early history of neurology and psychiatry in the Netherlands, the development of the specialty of neurology is discussed. During the 20th century the training of neurologists and the certification of specialists evolved from an informal master-fellow organization towards a strongly reglemented and legally based procedure. A nationwide Specialist Registration Commission supervises the quality of the training of specialists. Registered neurologists in the Netherlands are subject to a re-certification programme that controls the requirements to be fulfilled by the specialists such as their active involvement in patient care (for at least 16 h a week), attendance of the annual postgraduate courses in neurology (5-year cycle) and regular participation in international congresses of neurology. The undergraduate training in neurology, the neurology clerkship and the postgraduate training in neurosciences are described. Measures taken in order to maintain the balance between the supply of and the demand for neurological care in the near future are reported.     

Median and caudal apertures in the roof of the fourth ventricle in rodents and primates

In serial paraffin sections of brainstems fixed by perfusion, ventriculo-cisternal communications in the caudal part of the fourth ventricle are demonstrable in seven species of a total of 27 species, representing Marsupialia, Edentata, Lagomorpha, Rodentia, Ungulata, Carnivora, and Primates, in all of which the lateral apertures of Luschka are well developed. Caudal apertures appear as irregular defects in the taenia of the fourth ventricle with flattening of the roof against the surrounding leptomeninges over the crebello-medullary cistern in the guinea pig, the mulatta monkey, the squirrel monkey and the cynomolgus monkey. In addition, the one capuchin monkey and the one vervet monkey studied have a midline defect in the roof. In the capybara, a circular midline opening through the roof is closed off dorsally by the cerebellar vermis. These caudal and median defects are thought to be ruptures developed late in fetal life due to accumulation of cerebrospinal fluid before egress through lateral apertures of Luschka is established; although they seem to have served their purpose in the fetus and are no longer needed in the adult, they are kept open by continued flow. Study of fetuses from these selected species could prove useful to determine factors concerned with the development of cerebrospinal fluid circulation.     

Autoradiography of neurogenesis and morphogenesis in the regio cingularis of the rat. III. Migration and lamination in the regions of the cingulate cortex and the area postcentralis

The migration has been investigated in 171 embryonic and neonatal rats by means of autoradiographs, after injection of tritiated thymidine from E 18 to P 12 in 4 regions of the brain (Mesoarchicortex, Regio cingularis mesoneocorticalis, Area praecentralis angranularis, Area postcentralis). The migration begins at the third day after the injection. The localization of labeled cells was found in the cortical plate after injection in the early embryonic period and in the L II after injection in the late phasis always at the third day, the speed of migration increases in the course of embryonic development. The migration indicates in all regions an inside-out sequence. Cells from the last division migrates to the surface of the cortical plate. The cortical plate is a transitory element of the brain development. The lamination is possible earlier by means of the distribution pattern of labeled cells than with cytoarchitectonics and also the observation of areas.     

Changes in the size and organisation of the brain in man and his ancestors.

Changes in brain size are described during the evolution of man's ancestors and during man's development. It is shown that differences in size are accompanied by changes in the proportions of the brain, and that selection pressures have been greater for some parts than others.     

Interspecific differences in the expression of the AMPA-type glutamate receptors and parvalbumin in the nucleus of Edinger-Westphal of chicks and pigeons

The distribution of AMPA-type glutamate receptor (GluR) subunits was studied in the Edinger-Westphal nucleus (EW) of chicks and pigeons. GluR1, GluR2, GluR3 and GluR4 subunits appeared to be present in EW neurons of both species, but interspecific differences were observed in the abundance of the different types of subunits found in EW neurons. Of particular note, GluR2 immunoreactivity was present in the vast majority (ca. 80%) of neurons of pigeon EW but was found in only a small fraction (ca. 15%) of chick EW neurons. Scarcity of the GluR2 subunit in chick EW was confirmed by in situ hybridization. Because of the tendency for parvalbumin to be localized to neurons that are selectively deficient in GluR2, we also studied the localization of parvalbumin, as well as other calcium-binding proteins, in EW of chick and pigeon. Parvalbumin was found in more than 50% of chick EW neurons but was not detected in pigeon EW neurons. Our results suggest that there are major glutamatergic inputs to EW neurons in both pigeons and chicks. Furthermore, there are likely to be more AMPA-type calcium-permeable glutamate receptors in EW neurons of chick than in pigeon, since it is known that the subtype containing the edited GluR2 subunit is not calcium permeable.