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At least 1,639 records · Page 91Linked to original sources
PubMed1989

The development of long-term potentiation in hippocampus and neocortex.

The development of long-term potentiation (LTP), an enduring alteration in synaptic efficacy following afferent activation, was examined in CA1 hippocampus and primary visual cortex of rat. Both regions show little LTP prior to postnatal day 5, demonstrate a maximal potentiated response around postnatal day 15, and a subsequent decline to adult levels. These results are discussed with respect to the underlying mechanism of action and behavioral significance of these critical-period phenomena.

Aging↗
PubMed1983

"Stick out your tongue": tongue protrusion in neocortex and hypothalamic damaged rats.

Easily administered tests, analogues to the human neurological "stick out your tongue" tests, were devised to assess tongue use in normal, lateral hypothalamic (LH) and decorticate rats. LH and decorticate rats showed loss of tongue protrusion and licking immediately after surgery. Even though LH rats did not recover spontaneous eating dry food and drinking water, they showed extensive recovery of tongue protrusion and use. Decorticate rats regained the ability to eat dry food and drink water, but they showed minimal recovery of tongue protrusion and use. Comparisons of rats with variously located circumscribed neocortical lesions showed maximal tongue protrusion deficits followed orbital frontal cortex ablations. The results show: (1) that the tests developed and described are useful for routine examination of rats that have feeding abnormalities; (2) the feeding abnormalities of decorticate and LH rats can be dissociated; and (3) the orbital frontal cortex and corticofugal pathways passing through or adjacent to the LH may play a special role in the control of tongue and mouth use.

Animals↗
PubMedDate not supplied

Estrogen formation in the mammalian brain: possible role of aromatase in sexual differentiation of the hippocampus and neocortex.

Recent studies suggest that sex differences in cognitive function may involve effects of circulating androgens on the developing cerebral cortex and hippocampus. The mechanism of these effects is not understood. In rhesus monkeys, aromatase activity is present in the hippocampus and several areas of the cerebral cortex during late fetal and early postnatal life. Similarly, work in rats and mice indicates that the hippocampus and cerebral cortex may be capable of estrogen biosynthesis during early development. These results are consistent with the hypothesis that the actions of androgens on the developing cerebral cortex and hippocampus may involve local estrogen-mediated effects similar to those responsible for differentiation of the hypothalamic mechanisms controlling reproductive function.

Animals↗
PubMed1983

Loss of cholinergic neurons in the rat neocortex produces deficits in passive avoidance learning.

Bilateral kainic acid lesions of the ventral globus pallidus produced a significant and selective cortical decrease in choline acetyltransferase activity in the rat brain. When lesioned and control subjects were compared on performance of a step-through passive avoidance task, lesioned rats showed a marked retention deficit 24 hr after the initial training trial. This experimentally-induced memory deficit associated with a cortical cholinergic neuronal loss resembles the deficits in senile dementia of the Alzheimer type and may provide a useful animal model for studying the disease.

Acetylcholine↗
PubMed1990

Effect of partial removal of frontal or parietal bone on concentrations of mRNAs coding for preprocholecystokinin and preprosomatostatin in rat neocortex.

Partial removal of the frontal or parietal bone increased concentrations of mRNAs coding for preprocholecystokinin and preprosomatostatin in rat parietotemporal cortex by more than 170 and 67%, respectively, when measured 3 days after the operation. The increases were independent of the anaesthetic agent used during the operation and were transient with a maximum usually observed 3 days after the operation. They occurred not only in areas close to or under the removed bone part, but also in more distant areas. Thus, removal of the frontal bone also enhanced levels of preprocholecystokinin- and preprosomatostatin-mRNA in the parietotemporal and occipital cortex. mRNA concentrations were increased in the inner as well as outer layers of the cortex. The possible experimental and pathophysiological implications of the observed changes in gene expression of both neuropeptides in neocortical neurons are discussed.

Animals↗
PubMed1988

Estimation of the numerical density of synapses in rat neocortex. Comparison of the 'disector' with an 'unfolding' method.

The numerical density of synapses in the molecular layer of the parietal cortex of normal 28-day-old rats has been estimated by using two stereological methods, namely an unfolding technique and the disector method. For the unfolding technique it was assumed that the synapses formed a polydispersed population of disc-shaped particles. The technique also relies upon various assumptions regarding the size, shape and projection of synapses in the plane of section, these assumptions producing a result that is biased to an unknown extent. Such simplifying assumptions are unnecessary for the disector method. The mean +/- S.E.M. numerical density of synapses was found to be 2.16 +/- 0.14 x 10(9)/mm3 using the disector method. This was not significantly different (paired t-test; P less than 0.05) from the value of 2.41 +/- 0.22 x 10(9)/mm3 obtained using the unfolding technique with correction for truncation ('lost caps'). When the unfolding method was used without a correction for lost caps the numerical density was 1.98 +/- 0.10 x 10(9)/mm3, a value also not significantly different from that obtained using the disector method. The mean projected height (Hs) of the synaptic particles was also determined using both procedures; the results were not significantly different. When the variances of the final estimates and the time taken to carry out the procedures described were taken into account, it was estimated that the disector method was about 86% more efficient than the unfolding method with capping correction. Although the unfolding method can give essentially similar values for the numerical density of synapses to those obtained by the disector method, it is biased and much less efficient. It is concluded, therefore, that the disector method is the superior method for the estimation of the number and size of particles such as synapses, particularly when they have complex spatial configurations.

Animals↗