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PubMed1990

Macrophage-like cells in the presumptive optic pathways in the floor of the diencephalon of the chick embryo.

In the suboptic necrotic centres (SONCs) of the chick embryo diencephalon floor, large numbers of cells die in Hamburger and Hamilton's (HH) developmental stages 14-23. Until recently, it was thought that in these centres, the fragments of dead cells were phagocytosed exclusively by neighboring healthy cells but not by specialized macrophages. We now report morphological evidence of macrophage-like cells within the SONCs of the chick embryo. The distinctive features of these cells are their more or less spherical shape, a nucleus with a thin band of heterochromatin just beneath the nuclear envelope, and cytoplasm showing abundant digestive vacuoles and mitochondria with an electron-lucent matrix. These cells are capable of undergoing mitosis, and selectively stain with the histochemical technique for acid phosphatase. The macrophage-like cells are rare in SONCs in stages HH14-20 and become much more abundant in developmental stages just before the disappearance of these necrotic centres, suggesting that they phagocytose debris from the last cells to die in the SONCs. Acid phosphatase-positive mesenchymal cells with morphological features similar to those of macrophage-like cells are seen in intimate relationship with the basal surface of the SONCs in places where the basal lamina is sometimes missing. These observations suggest that macrophage-like cells in the SONCs arise from the underlying mesenchyme. Free macrophage-like cells with mitotic capacity are also seen in the ventricular lumen adjacent to the apical surface of the diencephalon floor in zones related to the presumptive optic pathways. These cells phagocytose cell debris shed from both the SONCs and from the partially disorganized areas in the neuroepithelium. In these latter we have identified mesenchymal cells with morphological features similar to the macrophage-like cells in the process of traversing the neuroepithelium from the mesenchymal compartment toward the ventricular lumen, thus suggesting that the intraventricular macrophage-like cells arise from the mesenchyme underlying the diencephalon floor.

Animals↗

PubMed1987

Distribution of catecholamine-containing cell bodies in the human diencephalon.

The distribution and morphological characteristics of catecholamine (CA)-containing cell bodies in the diencephalon of 7-9-month-old fetuses were studied by means of the Faglu histofluorescence method. Although the general distribution of CA cell bodies in human diencephalon observed in the present study is similar to that in other mammals, there are some significant differences. A great number of CA neurons lie within the lateroventral hypothalamic zone. There are more numerous larger CA neurons distributed outside the periventricular gray in the human diencephalon.

Catecholamines↗

PubMed2005

Sex differences in diencephalon serotonin transporter availability in major depression.

BACKGROUND: Major depression is more prevalent in women than men. The present study evaluated if previous findings that demonstrated decreased 5-hydroxytryptamine (5-HT) transporter availability in depressed patients would be confirmed in a larger sample and also evaluated sex differences. METHODS: Depressed (n = 32) and healthy subjects (n = 32), including 16 pairs of women and men, participated in an iodine-123-2 beta-carbomethoxy-3beta-(4-iodophenyltropane) ([(123)I]beta-CIT) single photon emission computed tomography (SPECT) and a magnetic resonance imaging (MRI) scan. Participants were administered [(123)I]beta-CIT (225.7 +/- 3.7 MBq) and imaged 23.0 +/- 1.6 hours later. Statistical analyses included analysis of variance and a regression analysis of the main and interactive effects of age, sex, and depression. RESULTS: Overall, depressed patients demonstrated 12% lower diencephalon and no change in striatal or brainstem [(123)I]beta-CIT uptake. Significant age by sex, sex by depression, and age by sex by depression interactions were noted due to 22% lower diencephalon [(123)I]beta-CIT uptake in depressed women compared with less than a 1% decrease in depressed men. CONCLUSIONS: As observed previously, diencephalon 5-HT transporter availability is decreased in depressed patients. However, the decrease appears to be sex-specific and age-dependent. These findings suggest that serotonergic mechanisms mediating depressed mood differ between men and women in an age-dependent manner and may explain why young women respond better to treatment with selective serotonin reuptake inhibitor (SSRI) antidepressants.

Adult↗

PubMed2006

Patterning the developing diencephalon.

The diencephalon is the embryonic precursor to the caudal forebrain. The major diencephalic derivative is the thalamus, which functions as a relay station between the cortex and lower nervous system structures. Although the diencephalon has been recognized as a vital brain region, our understanding of its development remains superficial. In this review, we discuss recent progresses in understanding one essential aspect of diencephalic development, diencephalic patterning. Signaling centers identified in the zona limitans intrathalamica and along the dorsal and ventral midlines have emerged as essential organizers in diencephalic patterning. The cumulative data reveal that the diencephalon shares some developmental principles with more caudal brain regions, whereas other mechanisms are unique to this region.

Animals↗

PubMed1996

An immunocytochemical mapping of beta-endorphin (1-27) in the cat diencephalon.

The distribution of beta-endorphin (1-27) immunoreactive cell bodies and fibres was studied in the diencephalon of the cat using an indirect immunoperoxidase technique. In the thalamus, almost all the immunoreactive fibres were found in the midline region and in nuclei located near the midline, whereas in the hypothalamus fibres containing beta-endorphin (1-27) were visualized extending by the whole structure. The hypothalamus showed a higher density of beta-endorphin (1-27) immunoreactive fibres than the thalamus, as well as immunoreactive cell bodies, since in the thalamus no beta-endorphin (1-27) immunoreactive neuron was located. The densest network of immunoreactive fibres was observed in the epithalamus (nucleus periventricularis anterior) and in the hypothalamic nuclei arcuatus, hypothalami ventromedialis, suprachiasmaticus, periventricularis hypothalami, hypothalamus dorsomedialis, area hypothalamica dorsalis, hypothalamus anterior, filiformis, hypothalamus posterior and regio praeoptica. In the hypothalamus, a high density of perikarya containing beta-endorphin (1-27) was observed in the nucleus arcuatus and a low density in the nucleus hypothalami ventromedialis. The distribution of beta-endorphin (1-27) immunoreactive fibres and perikarya is compared with the location of other neuropeptides in the cat diencephalon. Our findings reveal that b-endorphin (1-27) immunoreactive structures are widely distributed in the cat diencephalon, suggesting that the peptide might be involved in several physiological functions.

Animals↗

PubMed2000

Distribution of luteinizing hormone-releasing hormone in the upper brainstem and diencephalon of the cat: an immunocytochemical study.

The distribution of luteinizing hormone-releasing hormone (LH-RH)-immunostained cell bodies and fibres was studied in the brainstem and diencephalon of the cat using an indirect immunoperoxidase technique. The brainstem and the thalamus were devoid of immunostained cell bodies, whereas in the hypothalamus immunopositive perikarya were observed in the supraoptic nucleus, the anterior hypothalamus, the preoptic region and in the arcuate nucleus. Our findings also showed that the hypothalamus is richer in immunostained fibres, and that in this region such fibres are more widely distributed than in the thalamus and upper brainstem. No immunopositive fibres were observed in the lower brainstem. Our results point to a more widespread distribution of LH-RH-immunostained perikarya in the cat hypothalamus than that previously reported in the cat; a similar distribution to that found in the rat, and a more restricted distribution than in primates. Additionally, our study shows a more widespread distribution of immunostained fibres in the cat brainstem and diencephalon than that previously described for other mammals. In this context, our results describe for the first time in the mammals central nervous system fibres containing LH-RH located in the stria medullaris of the thalamus, the supramammillary decussation, the laterodorsal and lateroposterior thalamic nuclei, the nucleus reuniens, the supraoptic nucleus, and the optic chiasm. Thus, our findings reveal that LH-RH-immunostained structures are widely distributed in the upper brainstem and in the diencephalon of the cat, suggesting that the peptide may be involved in several physiological functions.

Animals↗

PubMed2001

Effect of food manipulation on the neuropeptide Y neuronal system in the diencephalon of ewes.

The expression of neuropeptide Y (NPY), which is involved in the neuromodulatory function associated with animal nutrition, growth and reproduction, depends on the nutritional status. However, the roles of individual components of food are not fully recognised. In this study, we evaluated the effects of dietary protein levels on the diencephalic population of NPY neurones. Female lambs were fed two diets equilibrated energetically but containing 8% protein in restricted diet or 18% protein in elevated diet, for 15 weeks starting with 6 months of age, during the first breeding period. Then, brain tissues were collected, fixed and used for the immunohistochemical localisation of NPY. Detection of NPY in diencephalon sections was followed by the image analysis and expressed as the percent area stained and optical density of immunostaining. Two distinct populations of the immunoreactive NPY perikarya were found, one in the infundibular nucleus; and the other in areas of diencephalon adjacent to the rostral hypothalamus. Long-term feeding the protein restricted diet caused a prominent expression of the immunoreactive material solely in the hypothalamic NPY neurones, particularly in those located in the entire periventricular area and in the infundibular nucleus. Both, percent area exhibiting positive staining and the density of immunoreactive NPY measured in the periventricular subdivision of the paraventricular nucleus were significantly higher (P<0.05) in sheep fed restricted diet, than in sheep fed on elevated diet. This study describes the distribution of NPY neurones in the sheep diencephalon, and shows the relationships between the expression of hypothalamic population of NPY neurones and the level of protein feeding.

Animals↗

PubMed2002

Expression pattern of cLhx2b, cZic1 and cZic3 in the developing chick diencephalon.

The diencephalon is the caudal part of the developing forebrain that gives rise to the epithalamus, thalamus, hypothalamus and retina. The mature diencephalon is functionally and anatomically parceled into well-defined nuclei. In an effort to understand how this region of the brain develops we examined the expression of several transcription factors during development. We find that the LIM homeodomain transcription factor, cLhx2b, and the zinc finger transcription factors, cZic1 and cZic3, are predominantly expressed in partially overlapping domains of the chick dorsal diencephalon. Interestingly, a correlation exists between their expression in neuroepithelial progenitor cells at early stages and in the differentiated nuclei at progressively more advanced stages of development.

Animals↗

PubMed2006

Infusions of 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP) to the ventral tegmental area, but not the substantia nigra, enhance exploratory, anti-anxiety, social and sexual behaviours and concomitantly increase 3alpha,5alpha-THP concentrations in the hippocampus, diencephalon and cortex of ovariectomised oestrogen-primed rats.

Sequential actions of 17beta-oestradiol (E2) and progesterone (P4) in the ventromedial hypothalamus (VMH) and ventral tegmental area (VTA) mediate sexual behaviour of female rodents. In the presence of appropriate environmental stimuli, E2 and P4 can facilitate initiation of sex behaviour (i.e. lordosis), in part through classic actions at intracellular progestin receptors in the VMH. However, the effects of P4 in the VTA to modulate lordosis involve its metabolite, 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP), which can have paracrine effects in the brain to reduce anxiety and stress. We investigated the effects of 3alpha,5alpha-THP infusions to the VTA, and a control site, the substantia nigra (SN), on exploratory, anti-anxiety, social and sexual behaviours (socio-sexual behaviours) and hormone levels in the midbrain and other regions (hippocampus, diencephalon and cortex) that may mediate these functions. Ovariectomised, rats were E2-primed (10 microg, s.c.) at 0 h and were infused with beta-cyclodextrin vehicle or 3alpha,5alpha-THP to the VTA or SN 44-48 h later. Ten minutes after infusions, rats were tested in the open field, plus maze, partner preference, social interaction and paced mating tasks, or served as nontested controls. Infusions of 3alpha,5alpha-THP to the VTA, but not the SN, increased central entries in the open field, open arm time in the plus maze, time spent in proximity to a male, duration of social interaction, incidence and intensity of lordosis, pacing, proceptivity, and anti-conflict behaviour. 3Alpha,5alpha-THP, but not vehicle, infusions to the VTA (but not the SN) also increased 3alpha,5alpha-THP levels in the midbrain, as well as the hippocampus, diencephalon and cortex. Behavioural testing increased levels of the precursor of 3alpha,5alpha-THP precursor, dihydroprogesterone (DHP). Thus, infusions of 3alpha,5alpha-THP to the VTA enhance socio-sexual behaviours and increase 3alpha,5alpha-THP levels in the hippocampus, diencephalon and cortex, and behavioural testing increases DHP levels in brain areas involved in modulating socio-sexual behaviours.

Animals↗

PubMed1983

Distribution of carboxylic esterases in the telencephalon and diencephalon of a microchiropteran bat (Taphozous melanopogon Temminck).

The contribution deals with the histoenzymological makeup of telencephalon and diencephalon of a microchiropteran bat which is considered to have a primitive type of brain. Three esterases, namely acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and nonspecific esterase (NSE), have been studied. In comparison with other mammalian brains the telencephalon and diencephalon of the bat demonstrate a high concentration of enzyme, especially in the nucleus caudatus and putamen, stria medullaris and the nuclei of the thalamus. AChE concentration is higher in neurons, while BChE is seen in almost all fibrous areas of the telencephalon and diencephalon. NSE activity is prominent in neurons and neuropil of neocortex, thalamus and hypothalamus. All the above data indicate that the brain of echolocating microchiropteran bats is metabolically much more active than that of other mammals. This is specifically true of the auditory system which is considerably specialized in these animals; this is also confirmed by the present histoenzymological study.

Acetylcholinesterase↗

PubMed1979

Quantitative changes in the fundamental structural pattern of the diencephalon among primates and insectivores.

The volumes of the main components of the diencephalon from 10 basal insectivores, 12 prosimians, and 15 simians including man were compared. The comparison of the percentage composition within the diencephalon shows that the thalamus and the subthalamus increase whereas the epithalamus and the hypothalamus decrease in relative size among primates. The allometric analysis reveals that, in spite of a relative reduction, the epithalamus and the hypothalamus are also progressive structures. However, their allometric size increase, being especially accentuated in earlier phyletic phases, is small in comparison to that of the thalamus and the subthalamus. These latter two components are characterized by a continuous phylogenetic growth from the basal insectivores to the simians. The correlation analysis shows that the strongest correlations and, in many cases, that isometric size increase exist between structures which belong to the same functional system. These findings indicate the existence of at least two major developmental gradients in the quantitative development of the diencephalon, a neencephalic and a limbic one.

Animals↗

PubMed2002

Close juxtapositions between LHRH immunoreactive neurons and substance P immunoreactive axons in the human diencephalon.

LHRH release is induced by substance P (SP) in the rat hypothalamus. Recent immunocytochemical studies indicate that SP-immunoreactive axons synapse on LHRH neurons in the diencephalon of the rat, but this phenomenon has not yet been demonstrated in human. Therefore, in the present study we visualized the SP- and LHRH-immunoreactive (IR) elements in the human diencephalon and evaluated the close juxtapositions between them. The distribution of LHRH- and SP-IR sites were investigated in diencephalic sections of six, postmortem human brains by means of double-labeling immunocytochemistry. The LHRH-containing perikarya were located in the diagonal band of Broca, lamina terminalis cinerea, preopticoseptal, medial preoptic, and infundibular areas of the brain. The SP-IR fibers formed a network in the periventricular zone in the infundibular region, median eminence, and corpus striatum. The SP-IR cell bodies were located mainly in the infundibular region, median eminence, basal part of the periventricular area, dorsomedial subdivision of the ventromedial nucleus, and basal perifornical area of the tuberal region. The juxtapositions between LHRH-IR cell bodies and SP-IR varicosities were detected in the infundibular and periventricular regions. In these sites black, silver-intensified, SP-IR fiber varicosities abutted on brown, DAB-labeled, LHRH-IR cell bodies. Similar structures were detected between the SP-IR fibers and SP-IR perikarya. These findings suggest that the juxtapositions between the SP and LHRH systems may be the morphological basis of SP-controlled LHRH release in the human diencephalon. Moreover, the intimate contacts between SP-IR fiber varicosities and SP-IR cell bodies or axons indicate direct control of SP on the diencephalic SP release.

Adult↗

PubMed2000

GAP-43 mediates retinal axon interaction with lateral diencephalon cells during optic tract formation.

GAP-43 is an abundant intracellular growth cone protein that can serve as a PKC substrate and regulate calmodulin availability. In mice with targeted disruption of the GAP-43 gene, retinal ganglion cell (RGC) axons fail to progress normally from the optic chiasm into the optic tracts. The underlying cause is unknown but, in principle, can result from either the disruption of guidance mechanisms that mediate axon exit from the midline chiasm region or defects in growth cone signaling required for entry into the lateral diencephalic wall to form the optic tracts. Results here show that, compared to wild-type RGC axons, GAP-43-deficient axons exhibit reduced growth in the presence of lateral diencephalon cell membranes. Reduced growth is not observed when GAP-43-deficient axons are cultured with optic chiasm, cortical, or dorsal midbrain cells. Lateral diencephalon cell conditioned medium inhibits growth of both wild-type and GAP-43-deficient axons to a similar extent and does not affect GAP-43-deficient axons more so. Removal or transplant replacement of the lateral diencephalon optic tract entry zone in GAP-43-deficient embryo preparations results in robust RGC axon exit from the chiasm. Together these data show that RGC axon exit from the midline region does not require GAP-43 function. Instead, GAP-43 appears to mediate RGC axon interaction with guidance cues in the lateral diencephalic wall, suggesting possible involvement of PKC and calmodulin signaling during optic tract formation.

Animals↗

PubMed1981

Skin-colour changes i the lizard, Anolis carolinensis, in response to localized electrical stimulation and lesions in the diencephalon.

A study was made of changes in skin colour in the lizard, Anolis carolinensis, in response to deep electrical stimulation at 0.2 mm intervals throughout the periventricular region of the diencephalon and the anterior brain stem. Double-barrelled glass microelectrodes with tip diameters of 3 microns were used. A 20 microA pulse-train consisting of a 500 Hz signal lasting for 1 s yielded localized responses. Skin darkening occurred only in response to stimulation delivered in the anterior and dorsal region of the diencephalon and skin lightening only in response to stimulation in a small area in the posterior and ventral region of the hypothalamus. Electrical lesions in the latter region resulted in permanent skin darkening. Surgical interruption of the hypothalamo-hypophysial neurosecretory tract did not block skin-colour change in response to dark or light backgrounds. It was concluded that MSH release is under tonic inhibitory control by hypothalamic neurones in Anolis. Both inhibitory and stimulatory neurones can be localized stereotaxically in the diencephalon and neither type corresponds with the neurosecretory neurones of the hypothalamo-hypophysial tract. The functional relationship between the stimulatory neurones and the inhibitory neurones and pars intermedia remains unclear.

Animals↗

PubMed1976

[Topography and cytoarchitecture of the diencephalon in the female comestic cattle (Bos taurus var. dom.)].

Ten brains of cows were, immediately after slaughter, embedded in celloidin, sliced, and stained to visualise neurocytes and nerve fibres, with the view to elucidating the structures of bovine diencephalon. Macroscopically, the diencephalon of cow is characterised by a comparatively strong epithalamic part, large laterally supported Corpora geniculata lateralis, pronounced ventricular bulgings, almost complete fusion of thalami with Massa intermedia, and very large pituitary gland. The five compartments of bovine interbrain are strongly developed and clearly delimitated by fibrous strings and platelets. By due consideration of the major fibre structures and cyto-architectonic characteristics, 62 nuclei may be differentiated in either half of the diencephalon, with 28 being situated in the thalamus and 23 in the hypothalamus. Two nuclear regions each were recordable from the epithalamus, metathalamus, and subthalamus.

Animals↗

PubMed1976

[Variations of the glucose 6 phosphodehydrogenase activity at the level of the diencephalon and of the gonads of the dormouse (Glis glis L.) during the annual cycle].

Activity levels of G6-PDH in the diencephalon and testes of Glis glis during the annual cycle show comparable variations. In the autumn, this activity is low and the gonads are inactive. At the anset of hibernation, this activity increases and becomes maximal during the period preceeding awakening. At mid-hibernation, the seminiferous tubules display in important enzymatic activity. Awakening is marked by a fall in enzymatic activity level that is a little more precosius of the diencephalon. The variations of enzymatic activity levels of G6-PDH in the diencephalon are similar in the female with an autumnal minimum and a maximal activity at the end of hibernation.

Animals↗

PubMed1991

[Composition of elements in the tissues of the rabbit hemispheres, diencephalon and brain stem in experimental mild cranio-cerebral trauma].

Measurements were made over time of the relative content of sodium, potassium, chlorine, phosphorus, sulfur and oxygen in the hemispheres, diencephalon and brain stem in rabbits with experimental craniocerebral injury (EMCCI). It has been established that the relative content of the elements measured was relatively stable in the hemispheres, whereas in the diencephalon and brain stem, it was prone to appreciable fluctuations. In the diencephalon and brain stem, the relative oxygen content dropped after 15 minutes, 7 and 14 days, that in the hemispheres reduced after 14 days. After 15 minutes and 2 hours there was an increase of the portion of chlorine and sodium; after 14 days there was a rise of the relative content of phosphorus and sulfur. The changes discovered point to the modification of the metabolic activity of the nerve tissue, seen during EMCCI. They also attest to the development of compensatory adaptive and pathological alterations.

Animals↗

PubMed1982

[Aromatase activity by the diencephalon of fetal and neonatal rats].

Aromatase activity in the diencephalon was investigated during the perinatal period in which sex differentiation occurs critically in the rat. 1) Fetal plasma testosterone levels at 17 and 20 days of gestation were slightly higher in the male than in the female. During the critical period after delivery, the hormone levels in the male neonates increased markedly, while it decreased rapidly in the female. 2) Aromatase activity was followed in the diencephalon by measuring the production of estradiol from a labelled substrate, 4-14 C-testosterone. Considerable enzyme activity was detected at 14 days of gestation and it decreased slightly thereafter. The enzyme activity, however, increased drastically during the postnatal critical period. After that it decreased again in both male and female neonates. 3) Aromatase in the telencephalon showed very weak activity with a fluctuation similar to that in the diencephalon. These results suggest that estrogens in the male pups which are specifically converted from testosterone during the critical period may be decisive in sex differentiation of the central nervous system in the rat.

Age Factors↗