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At least 433 records · Page 24Linked to original sources
PubMed1987

Neurotensin immunoreactive neurons in the human infant diencephalon.

Neurotensin-like immunoreactive (NT-IR) neurons are present in discrete subregions of the anterior, medial and lateral thalamic nuclear groups of the human infant brain. The pulvinar is notably rich in such cells. Smaller numbers of cells are present in the ventral group, centromedian nucleus, reticular nuclei and intralaminar nuclei. Neurotensin immunoreactive axons accumulate dorsally in the thalamus and cross the deep white matter. The cerebral cortex contains a rich network of NT-IR axons. The subthalamic nucleus is rich in NT-IR neurons. Within the hypothalamus NT-IR perikarya are present in parts of the lateral and tuberal regions and in the lateral mammillary area. NT-IR axons are widespread being particularly prominent in parts of the tuberal region and the mammillary body.

Diencephalon↗
PubMed1989

Regulation by estradiol of GABAA and GABAB binding sites in the diencephalon of the rat: an autoradiographic study.

Using in vitro quantitative autoradiography we studied the in vivo effects of estradiol on GABAA and GABAB receptors in the rat brain. In all the areas studied (suprachiasmatic nucleus, medial preoptic area, striatum, frontal cortex), estradiol failed to significantly affect the GABAA receptor density. Chronic treatment with estradiol led however in the suprachiasmatic nucleus and the striatum to a decrease in the density of GABAB receptors. GABAB receptor regulation by estradiol was found to be area-specific within the hypothalamus since it was not observed in the medial preoptic area. The down regulation of GABAB receptors in the suprachiasmatic nucleus induced by estradiol treatment might thus explain the inhibitory effect of the steroid on the GABA control of serotonin metabolism we recently reported.

Animals↗
PubMed1990

Abnormal retinal projections alter GAP-43 patterns in the diencephalon.

In Syrian hamsters, mature retinal terminals contain only low levels of the growth-associated protein, GAP-43, whereas the lateral posterior nucleus (LP) of the thalamus contains high levels of this protein. Damage to the superior colliculus in neonatal hamsters induces retinal terminals to form dense patches of innervation in the LP, an area which otherwise receives little if any direct retinal input. The present study used GAP-43 antibodies to examine the interaction between abnormally routed optic fibers and the cells in the anomalous thalamic target zone. Immunohistochemistry revealed very little GAP-43 in the abnormal retinal projection to the LP, indicating that the normal developmental decline in GAP-43 levels occurs even in an inappropriate extracellular environment. Moreover, retinal fibers were found to exclude the protein from its normal territory, forming negatively-stained islands in those regions of the LP containing the retinal terminals. In order to identify the normal source of GAP-43-positive terminals in the LP, we surgically removed two major extrinsic afferents to this region, or we chemically eliminated local interneurons. Whereas removing projections from the SC or posterior cortex did not alter GAP-43 immunoreactivity in the LP, destruction of local interneurons with ibotenic acid resulted in markedly diminished levels of this protein. These results show that retinal terminals induced to form in an abnormal target area undergo their normal diminution of GAP-43, and that these retinal projections displace other GAP-43-rich terminals in the LP that appear to arise from local interneurons.

Animals↗
PubMed1991

Characterization and distribution of estrogen receptors in the diencephalon of the gray short-tailed opossum.

The Brazilian gray short-tailed opossum is a pouchless marsupial whose young are born sexually undifferentiated making this animal ideal for developmental studies. Previously, Etgen and Fadem (Dev. Brain Res., 49 (1989) 131-133; Gen. Comp. Endocrinol., 66 (1987) 441-446) detected estrogen receptor (ER) in the hypothalamus-preoptic area, and compared males and females in the adult and during development. In this study we characterized the ER and determined its distribution in specific diencephalic regions in the brains of adult male and female opossums. ER were measured by the in vitro binding of [3H]estradiol to cytosol of microdissected brain nuclear regions. Radioinert moxestrol (R2858) was used to define non-specific binding. Saturation analysis showed a single high-affinity binding site. Binding was displaced by estradiol (E2), diethylstilbestrol (DES) and R2858, but not by non-estrogenic steroids. Ligand bound receptor adhered to DNA-cellulose and was eluted as a single peak with 0.2-0.3 M NaCl. High levels of ER were found in the medial preoptic-periventricular area. Intermediate levels were seen in the ventromedial hypothalamic nucleus, medial amygdala and arcuate nucleus. No sex differences were observed. The presence of a neural ER and its similarity of distribution to that of the laboratory rat support the use of this animal model in studies examining steroid dependent organization of the hypothalamus.

Animals↗
PubMed1992

Changes in rapidly transported proteins associated with development of abnormal projections in the diencephalon.

The development of the hamster visual system is accompanied by striking changes in the pattern of proteins that are synthesized in retinal ganglion cells and rapidly transported to their nerve terminals. To determine whether any of these protein changes are regulated by interactions between the developing nerve endings and the cells with which they form synapses, we induced retinofugal axons to form abnormal projections in the lateral posterior (LP) nucleus of the thalamus and dense patches of hyperinnervation in the lateral geniculate nucleus (LGN) by removing their principal target, the superior colliculus (SC), the day after birth. Under these experimental conditions, two rapidly transported proteins, including the neural cell adhesion molecule, NCAM, showed significant changes in their time course of expression. NCAM, identified here using a monospecific antibody, is normally synthesized and transported at high levels at early stages of development and then declines during the second and third postnatal weeks. However, this decline was delayed when optic fibers were re-routed. A second rapidly transported protein, M(r) = 67 kDa, pI = 4.7, normally shows a rise in its synthesis and transport during terminal arbor formation and a subsequent decline, but it also remained elevated for a prolonged period when the SC was absent. These findings cannot be accounted for by a simple delay in the retinal ganglion cells' program of axonal growth, since other rapidly transported proteins, including the growth-associated protein GAP-43, showed a normal developmental time-course when the SC was removed. Target interactions therefore appear to influence the retinal ganglion cells' expression of different proteins in a specific fashion.

Aging↗
PubMed1995

Efferent connections from the anterior pretectal nucleus to the diencephalon and mesencephalon in the rat.

The anterior pretectal nucleus has been described as part of the visual pretectal complex. However, several electrophysiological and behavioural studies showed that this area is involved in somatosensory modulation, more specifically, antinociception. The efferents of the anterior pretectal nucleus have not been identified taking into account the different function of this nucleus in relation to the rest of the pretectal complex. In the study herein described, a sensitive anterograde tracer Phaseolus vulgaris leucoagglutinin was used to trace the mesencephalic and diencephalic efferents of the anterior pretectal nucleus in the rat. The majority of the connections were ipsilateral. Fibres with varicosities were observed in discrete areas of the thalamus (central lateral, posterior complex), hypothalamus (lateral, posterior and ventromedial), zona incerta, parvocellular red nucleus, intermediate and deep layers of the superior colliculus, central grey, deep mesencephalon, pontine parabrachial region, and pontine nuclei. Fibres en passant were detected in the medial lemniscus, from the level of the injection site to rostral medullary levels. Some labelled axons were seen coursing to the contralateral side through the posterior commissure and the decussation of the superior cerebellar peduncle. These results show that the anterior pretectal nucleus projects principally to areas involved in somatosensory and motor control in a manner that permits sensory modulation at higher and lower levels of the brain. These connections may explain the antinociceptive and antiaversive effects of stimulating the anterior pretectal nucleus in freely moving animals.

Animals↗