Biomedical subjects

V Chao

Publications and source records attributed to V Chao.

4 recordsLinked to original sources

PubMed1999

Synaptogenesis of mossy fibers induced by spatial water maze overtraining.

Synaptic plasticity has been proposed as a mechanism underlying learning and memory. Synaptic reorganization of hippocampal mossy fibers has been observed after experimentally induced epilepsy, and after brief high-frequency activation inducing long-term potentiation. Furthermore, it has been suggested that synaptic changes in the hippocampus may occur after spatial learning. In this study, by using a zinc-detecting histologic technique (Timm), we demonstrate a significant increase of mossy fiber terminals in the CA3 stratum oriens region induced by training rats during 3 days in a spatial Morris water maze. In contrast, animals trained for only 1 day and animals that were just allowed to swim or were overtrained in a stress-motivated inhibitory avoidance task did not show increments of mossy fiber terminals in the stratum oriens. Electron microscopy confirmed that synaptic density of mossy fiber terminals in the stratum oriens increases significantly in water maze overtrained animals compared with the swimming control animals. Taken together, these results suggest that overtraining in a spatial learning task induces mossy fiber synaptogenesis that could be involved in the mechanisms underlying long-term memory storage. Hippocampus 1999;9:631-636.

Analysis of Variance↗

PubMed1998

The NMDA receptor antagonist CPP impairs conditioned taste aversion and insular cortex long-term potentiation in vivo.

It has been proposed that long-term potentiation (LTP) a form of activity-dependent modification of synaptic efficacy, may be a synaptic mechanism for certain types of learning. Recent studies on the insular cortex (IC) a region of the temporal cortex implicated in the acquisition and storage of conditioned taste aversion (CTA), have demonstrated that tetanic stimulation of the basolateral nucleus of the amygdala (Bla) induce an N-methyl-d-aspartate (NMDA) dependent LTP in the IC of adult rats in vivo. Here we present experimental data showing that intracortical administration of the NMDA receptor competitive antagonist CPP (-3(-2 carboxipiperazin-4-yl)-propyl-1-phosphonic acid) disrupts the acquisition of conditioned taste aversion, as well as, the IC-LTP induction in vivo. These findings are of particular interest since they provide support for the view that the neural mechanisms underlying NMDA dependent neocortical LTP, constitute a possible mechanism for the learning related functions performed by the IC.

Animals↗

PubMed1998

In vivo long-term potentiation in the insular cortex: NMDA receptor dependence.

It has been demonstrated that the insular cortex (IC) plays an important role in the acquisition and storage of different aversive motivated learning tasks like conditioned taste aversion, spatial maze and inhibitory avoidance. It is of particular interest to investigate whether activity-dependent modification of synaptic efficacy, a presumptive mechanism for learning and memory, is present in this cortical region. Here, we address this issue by examining the induction of synaptic plasticity, long-term potentiation (LTP) in in vivo preparations. The results showed that high frequency stimulation of the basolateral amygdaloid nucleus (Bla) induced LTP in the IC. The LTP induced by tetanus was blocked by application of the N-methyl-D-aspartate (NMDA) receptor antagonists CPP and MK-801, indicating that NMDA receptors were responsible for its induction. These results suggest that in vivo tetanus induced LTP of the Bla-IC projection is a possible mechanism for the memory-related functions performed by the IC.

Amygdala↗

PubMed1997

Tissue distribution of estrogen receptors alpha (ER-alpha) and beta (ER-beta) mRNA in the midgestational human fetus.

We compared the expression profiles of the mRNAs of both estrogen receptors, ER-alpha and the recently cloned ER-beta, in the midgestational human fetus by semiquantitative RT-PCR. ER-alpha was most abundant in the uterus, and smaller quantities were detected in the ovary, testis, skin and gut. High amounts of ER-beta mRNA were present in fetal ovaries, testes, adrenals and spleen. In these tissues, the levels of ER-beta mRNA were higher than ER-alpha. In the uterus, however, ER-alpha mRNA was more abundant, and ER-beta mRNA was expressed only moderately. ER-beta mRNA was present at moderate to low levels in the thymus, pituitary gland, skin, lung, kidney and brain cortex. In the course of our work, using the ER-beta primers on genomic DNA, an intron of 2468 bp in length, located between nt 222 and 223 in the A/B domain of ER-beta cDNA, was detected, cloned and sequenced. The study shows that the expression profile of the two ERs is different, and ER-beta is expressed in a variety of tissues during human fetal development, suggesting different, organ-specific roles for the two receptors.

Cloning, Molecular↗