Biomedical subjects

P Voorn

Publications and source records attributed to P Voorn.

46 records · Page 3Linked to original sources

PubMed1989

Prenatal development of GABA-ergic neurons in the neocortex of the rat.

The present study shows that in the prenatal rat neocortex the GABA immunoreactive neurons are not limited to the marginal, subplate, and intermediate zones, but are also found in all fetal zones of the cerebral anlage. The first GABA-ergic cells are observed on embryonic day 14 in the plexiform primordium. On embryonic day 15, a second population of GABA-ergic cells is observed in the intermediate zone. Beginning on day 16 of gestation and continuing throughout gestation, GABA-ergic neurons are observed in the marginal zone, the subplate zone, the cortical plate, and the ventricular and subventricular zones. Furthermore, while the number of GABA-ergic cells in the cortical plate increases, GABA-ergic neurons in the intermediate zone and subventricular zone decrease in number after embryonic day 19.

Animals↗

PubMed1988

Development of the dopaminergic innervation in the prefrontal cortex of the rat.

The pre- and postnatal development of the dopaminergic innervation in the prefrontal cortex (PFC) of the rat is described from embryonic day 14 through postnatal day 90. By embryonic day 15 the dopamine (DA)-containing fibers reach the anlage of the lateral neocortex; 2 days later the first fibers have reached the subplate of the future prefrontal cortex. The process of entering the cortical plate starts just before birth. Prenatally, some dopaminergic fibers can be observed in the marginal zone of both the lateral and the medial wall of the hemisphere. Within 48 hours after birth a large number of dopaminergic fibers can be observed in the marginal zone, i.e., the future layer I, in some subareas of the PFC. A transient appearance of DA-positive fibers is noticed in the late embryonic and early postnatal periods especially in the marginal zone and possibly in the superficial layers of the pregenual cingulate cortex. Changes in the morphology of DA fibers at P4 suggest that the actual DA innervation starts at this age. From postnatal day 6 the different subareas of the PFC can be recognized according to the characteristics of the topographical distribution of the dopaminergic fibers. Until postnatal day 60 the density of the dopaminergic fibers continues to increase. No difference in density and topography was observed between postnatal days 60 and 90.

Aging↗

PubMed1988

The pre- and postnatal development of the dopaminergic cell groups in the ventral mesencephalon and the dopaminergic innervation of the striatum of the rat.

In the adult rat the striatum is a compartmentalized structure, which is reflected in the inhomogeneous distribution of dopamine. As a first step to test the hypothesis that dopamine plays an organizational role in the development of the striatum, the ontogeny of the dopaminergic system was studied in detail with immunocytochemical methods employing antibodies against dopamine. Rat embryos, fetuses, pups and adults were perfusion-fixed with glutaraldehyde on all prenatal days from E11 onward, postnatally on P2, P4, P6, P7, P8, P13, P14, P20, P21, and in adult age. On E13 the first dopaminergic cells are detected in the ventral prosencephalon. On E14 two dopaminergic cell groups are present in the ventral mesencephalon, and fibres of these cells reach the ventrolateral part of the ganglionic eminence. In the next two days both the cell groups and their projections rapidly increase in size. On E17 the afferent dopaminergic fibres to the striatum become aligned and form huge bundles that are closely associated with the fascicles of the internal capsule. Rostrally, the development of the striatal dopaminergic innervation shows a clear ventrolateral to dorsomedial gradient, whereas more caudally the dopaminergic fibres innervate the striatum from a ventromedial position. The lateral parts of the otherwise compact mesencephalic cell groups consist of loosely arranged cells. From E17 onward these cells become arranged into a dorsal and a ventral group. Just before birth, on E21, the primordia of the dopaminergic cell groups in the substantia nigra pars compacta and pars reticulata can be observed. On E19 several centres with extensive fibre ramifications along the dorsolateral margin of the caudate putamen represent the first signs of the inhomogeneous distribution of dopaminergic fibres in the dorsal striatum seen during the next two weeks. In the following pre- and postnatal days these so-called dopaminergic "patches" also appear more medially. By the third postnatal week most of the patches are no longer detectable, and only the most dorsolaterally located ones, i.e. in the region where they first were detected on E19, remain visible through to the adult stage. Prenatally, no varicosities can be observed in the dopaminergic fibres. The first varicosities appear after birth. Their number increase rapidly during the first and second postnatal weeks and reaches near adult levels on P20. The development of the striatal dopaminergic innervation, and that of the "patches" in particular, is discussed in relation to the development of the mesencephalic dopaminergic cell groups.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗

PubMed1987

Increase of enkephalin and decrease of substance P immunoreactivity in the dorsal and ventral striatum of the rat after midbrain 6-hydroxydopamine lesions.

Unilateral 6-hydroxydopamine lesions of the mesostriatal dopaminergic system in the rat resulted in a decrease of substance P-immunoreactivity in the ventral striatum, and in a heterogeneously distributed increase of enkephalin-immunoreactivity in the dorsal and ventral striatum and the globus pallidus. The respective decrease and increase are caused by a lower or higher staining intensity of the peptidergic fibers, whereas no changes were found in the cell bodies.

Afferent Pathways↗

PubMed1987

Mesotocin and vasotocin in the brain of the lizard Gekko gecko. An immunocytochemical study.

The distribution of mesotocin and vasotocin was studied in the brain of the lizard Gekko gecko with antisera specific for either peptide. Both mesotocinergic and vasotocinergic perikarya are found in the paraventricular and supraoptic nuclei of the hypothalamus, whereas vasotocinergic neurons are exclusively present in the bed nucleus of the stria terminalis and in a cell group of the rhombencephalon. The distributional pattern of the mesotocinergic fibers corresponds closely to that of the vasotocinergic fibers. However, throughout the entire brain the mesotocinergic innervation is less dense than the vasotocinergic innervation. No sex differences are present in the mesotocinergic fiber system.

Animals↗

PubMed1986

The distribution of dopamine immunoreactivity in the forebrain and midbrain of the lizard Gekko gecko: an immunohistochemical study with antibodies against dopamine.

The distribution of dopamine (DA) immunoreactivity in the forebrain and the midbrain of the lizard Gekko gecko was studied by using recently developed antibodies against DA. Dopamine-containing cells were found around the glomeruli of the olfactory bulb, in several parts of the periventricular hypothalamic nucleus, in the periventricular organ, the ependymal wall of the infundibular recess, the lateral hypothalamic area and the pretectal posterodorsal nucleus of the diencephalon, and in the ventral tegmental area, the substantia nigra, and the presumed reptilian equivalent of the mammalian A8 cell group of the mesencephalon. Dopaminergic fibers and terminals were observed throughout the whole brain, but particularly in the diencephalon and the telencephalon. The nucleus accumbens appears to have the most dense innervation, but also the striatum, amygdaloid complex, olfactory tubercle, septum, and dorsal ventricular ridge (especially its superficial zone) show numerous DA-containing fibers and terminals. Except for the lateral cortex, cortical areas are not densely innervated by DA fibers. In several respects DA distribution in the gekkonid brain differs from that in other reptiles studied. For instance, in the Gekko the dorsal ventricular ridge is densely innervated by DA fibers, whereas in turtles and crocodiles the same structure shows only weak catecholaminergic histofluorescence. When compared to the distribution of DA immunoreactivity in mammals, it appears that the DA system in the gekkonid telencephalon resembles the distribution of DA in the limbic forebrain and striatum of mammals. Whether these similarities in distribution of DA also imply similarities in function will be discussed.

Animals↗

PubMed1986

The dopaminergic innervation of the ventral striatum in the rat: a light- and electron-microscopical study with antibodies against dopamine.

Dopamine (DA) in the dorsal and ventral striatum is associated with different aspects of locomotor activity control. The ventral striatum may form an interface between the limbic system and the extrapyramidal motor system. The distribution of dopaminergic fibers in this interface position was studied in detail with a method applying antibodies against DA. Furthermore, the ultrastructural morphology of the DA fibers was examined by means of immuno-electron microscopy. The results show that DA immunoreactivity is distributed over the ventral striatum in a highly compartmentalized fashion. In the dorsal striatum few compartments were found. The DA fibers in the ventral striatum establish mainly symmetric synaptic contacts, preferably with dendritic shafts and spines. The results are discussed in relation to previous data concerning the light and electron-microscopic identification of catecholaminergic fibers in the ventral and dorsal striatum.

Animals↗

PubMed1985

The distribution of hypothalamic and extrahypothalamic vasotocinergic cells and fibers in the brain of a lizard, Gekko gecko: presence of a sex difference.

The distribution of vasotocin in the brain of the lizard Gekko gecko was studied with immunocytochemical methods. Vasotocinergic cells were found in the nucleus supraopticus, the nucleus paraventricularis, the bed nucleus of the stria terminalis, and in the rhombencephalon. Vasotocinergic fibers were found in the preoptic area, the lateral and ventral hypothalamus, and in many extrahypothalamic brain areas. Furthermore, evidence was obtained of a conspicuous sex difference with regard to vasotocinergic innervation of the lateral septum, the ventrocaudal telencephalon (nucleus sphericus), and the periaqueductal gray; in these areas vastocinergic innervation is much denser in males than in females. The results are discussed in relation to the sexually dimorphic vasopressinergic innervation of the rat brain. It is suggested that the vasotocinergic fiber system in the sexually dimorphic brain areas in Gekko gecko is related to the bed nucleus of the stria terminalis.

Animals↗

PubMed1983

An immuno-electronmicroscopical study comparing vasopressin, oxytocin, substance P and enkephalin containing nerve terminals in the nucleus of the solitary tract of the rat.

Vasopressin, oxytocin, substance P and enkephalin fibers were demonstrated to terminate synaptically in the nucleus of the solitary tract. The detergent Triton X-100 proved to be indispensable for the demonstration of vasopressin and oxytocin while enkephalin and substance P could be visualized very well without it. The differences with respect to morphology between these 4 peptides disappeared when Triton X-100 was used in both groups.

Animals↗

PubMedDate not supplied

Nuclear origin of thalamic afferents of the ventral striatum determines their relation to patch/matrix configurations in enkephalin-immunoreactivity in the rat.

The relation of thalamic terminal fibers in the ventral striatum with patch and matrix compartments, as defined by enkephalin-immunohistochemistry, was studied in adjacent or double-stained sections of the rat brain by combining anterograde tracing of Phaseolus vulgaris-leucoagglutinin (PHA-L) and enkephalin staining. Experiments with small PHA-L injections in the dorsal thalamus show that the paraventricular thalamic nucleus projects to the medial nucleus accumbens and rather selectively to the patch compartment in more lateral parts of the nucleus. The central medial thalamic nucleus sends its fibers to more lateral parts of the nucleus accumbens and the ventral part of the caudate-putamen, where these fibers terminate in the matrix compartment.

Afferent Pathways↗