Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Entorhinal Cortex”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,549 records · Page 86Linked to original sources
PubMed1988

Tracer 2-deoxyglucose kinetics in brain regions of rats given kainic acid.

The initial distribution of tracer amounts of 2-deoxyglucose between plasma and brain tissue, relative to native glucose, and the rate of accumulation of 2-deoxyglucose-6-phosphate were determined in brain regions of rats given kainic acid intravenously. Regional plasma flow was measured in a comparable group of animals. A previously described compartmental model was used to obtain estimates of rates of glucose transport and of glucose phosphorylation. Both rates were significantly increased in entorhinal cortex, hippocampus, amygdala, and septal nucleus. From measured brain tissue and plasma glucose concentrations, glucose fluxes were also calculated in terms of either irreversible or reversible Michaelis-Menten kinetics. In all brain regions of control rats and in six of the ten regions studied in rats given kainic acid, rates of glucose transport calculated in terms of the Michaelis-Menten models were consistent with those estimated by the tracer 2-deoxyglucose procedure. However, in the four regions in which glucose metabolism was stimulated, rates of glucose transport calculated from the behaviour of tracer 2-deoxyglucose were considerably higher than rates calculated from measured concentrations of glucose in plasma and brain tissue using Michaelis-Menten models. The possibility is considered that in those regions that are metabolically stimulated by kainate, there is an increasing asymmetry between the luminal and abluminal membranes of the capillary endothelium in the permeability to glucose and its analogs. An alternative proposal is that in the model used to analyse the tracer 2-deoxyglucose data, the assumption of a rapid mixing of tracer throughout the endogenous pool of tissue glucose prior to phosphorylation becomes invalid. The discrepancies between tracer and native glucose in these particular regions of rats given kainate are consistent with an apparent metabolic compartmentation. The influence of kainate on plasma flow was found to differ regionally, with flow in entorhinal cortex, hippocampus, and amygdala being unchanged. There is some evidence for increased rates of glycolysis relative to oxidative metabolism in these regions.

Animals↗
PubMed2003

Quantitative analysis of axon collaterals of single cells in layer III of the piriform cortex of the guinea pig.

Recent physiological and morphological studies suggest that the piriform cortex (PC) functions like the association areas of the neocortex rather than the typical primary sensory area as was previously assumed. The axon connection patterns of single cells are important for understanding the functional organization of the PC. The axon collaterals of three single pyramidal cells and one spiny multipolar cell in layer III of the PC were labeled and quantitatively analyzed by intracellular injections of biocytin in guinea pigs. The individual pyramidal and spiny multipolar cells have highly distributed axon collaterals, which display little tendency for patchy concentrations, within the PC and multiple higher order behavior/reward/contextual-related areas, such as the prefrontal cortex, amygdaloid nuclei, and entorhinal cortex. For the pyramidal cells, the average length of axonal collaterals is 143 mm; the average number of boutons is 12,930. For the spiny multipolar cell, the length of the axonal collaterals is 88 mm; the number of boutons is 7,052. The pyramidal cells in the anterior subdivision of the PC (APC) have both rostrally and caudally directed intrinsic association fibers, whereas the pyramidal and spiny multipolar cells in the posterior subdivision (PPC) have predominantly caudally directed intrinsic association fibers in the PC. Our results reveal that the connection patterns of single cells in layer III resemble those of pyramidal cells in layer II, suggesting that the PC performs correlative functions analogous to those in the association area of other sensory systems. The rostrally-to-caudally directed connections in the APC provide a substrate for the recurrent process, whereas largely caudally directed connections in the PPC suggest the dominance of the feed-forward process.

Animals↗
PubMed1983

The laminar distribution of intracortical fibers originating in the olfactory cortex of the rat.

In this study, the autoradiographic method for tracing axonal connections was used to identify the laminar distribution of intracortical fibers originating in the olfactory cortical areas of the rat. Most of the projections can be divided into two major fiber systems with different laminar patterns of termination. The first of these, termed the layer Ib fiber system, arises in the anterior olfactory nucleus, the anterior and posterior piriform cortex, and the lateral entorhinal cortex, and terminates predominantly in layer Ib and, in many cases, layer III of the entire olfactory cortex. The second system, termed the layer II-deep Ib fiber system, originates in three relatively small olfactory cortical areas--the dorsal peduncular cortex, the ventral tenia tecta, and the periamygdaloid cortex--and terminates in and around the cells of layer II in most parts of the olfactory cortex. There is significant overlap in the laminar distribution of the two systems, although the distinction between them is readily apparent. Within the layer Ib fiber system there are relatively slight but consistent differences in the lamination of fibers from different areas. The fibers from the anterior olfactory nucleus are concentrated in the deep part of layer Ib while those from the anterior piriform cortex are concentrated in the superficial part of this layer. The fibers from the posterior piriform cortex tend to be densest in the middle of layer Ib. These differences are maintained in all areas of termination of each set of fibers, both ipsilaterally and contralaterally. In addition, intracortical fibers from the anterior cortical nucleus of the amygdala are distributed throughout layer I, including layer Ia and Ib. Fibers from the nucleus of the lateral olfactory tract terminate bilaterally around the cells of the islands of Calleja and the medial edge of the anterior piriform cortex.

Amygdala↗
PubMed1994

Localization of somatostatin (SRIF) SSTR-1, SSTR-2 and SSTR-3 receptor mRNA in rat brain by in situ hybridization.

In situ hybridization histochemistry was performed to analyse the distribution of the messenger RNA (mRNA) of three putative somatostatin (SRIF) receptors in rat brain, using oligonucleotide probes derived from the cDNA coding for SSTR-1, SSTR-2, and SSTR-3 receptors. SSTR-1 signals were found in layers V-VI of the cerebral cortex, in primary olfactory cortex, taenia tecta, subiculum, entorhinal cortex, granular layer of the dentate gyrus, amygdala and cerebellar nuclei. Signals for SSTR-2 were found in the frontal cerebral cortex (layers IV, V and VI), taenia tecta, claustrum, endopiriform nucleus, locus coeruleus, medial habenula, subiculum, granular cell layer of the dentate gyrus and amygdala. High levels of SSTR-3 hybridization were found in the olfactory bulb, primary olfactory cortex, islands of Calleja, medial habenula, amygdala, granular layer of the dentate gyrus, various thalamic and pontine nuclei and in the granular and Purkinje cell layers of the cerebellum. The distribution of the hybridization signals of the oligoprobes is consistent with the labelling of specific SRIF binding sites in rat brain. Especially, SSTR-2 and SSTR-1 oligos seem to label regions in which SS-1 and SS-2 receptors, respectively, have been previously characterized in autoradiographical studies. The situation is less clear with SSTR-3 mRNA, since SRIF binding in adult rats is usually low or absent in cerebellum, although some cerebellar nuclei appear to be labelled in the adult. The localization of SSTR-1, SSTR-2 and SSTR-3 mRNAs suggests that SRIF receptor subtypes in rat brain show profound differences in their distribution and are involved in a variety of central, in addition to neuroendocrine, functions.

Animals↗
PubMed1984

Brain stimulation reward and dopamine terminal fields. II. Septal and cortical projections.

The boundaries and relative sensitivities of the substrates of septal and cortical brain stimulation reward were mapped in relation to the dopamine terminal fields in these regions using a dorsal-ventral moveable electrode. Brain stimulation was rewarding at all levels of the posterior lateral septum and not just in the region of dopamine terminal innervation. Reward thresholds, ease of training, maximum response rates and stability of responding were all unrelated to the proximity of the stimulating electrode to the band of dopamine terminals revealed by glyoxylic acid-induced dopamine fluorescence. Stimulation was also rewarding in the anterior lateral septum; the best sites were in the ventral portions of this region although dopamine terminal fluorescence was uniform throughout. Thus the anatomy of the brain stimulation reward substrate of the lateral septal nucleus does not bear a special relation to the anatomy of dopamine terminals within this region. Stimulation was also rewarding in each of the dopamine terminal fields of the cerebral cortex. The best self-stimulation was obtained with electrodes in the medial frontal cortex; sulcal frontal cortex was next best, entorhinal cortex was next, and pyriform cortex, though reliably positive, supported the weakest self-stimulation. Variations in self-stimulation threshold were seen as electrodes were moved through homogeneous regions of dopamine terminal density in some regions, while stable thresholds were associated with movements through areas of varying dopamine terminal density in others; thus, again, there was no special relation between goodness of self-stimulation and density of dopaminergic innervation. These data suggest that rewarding brain stimulation in these regions is not due to direct activation of either the dopaminergic terminals or the cells that they innervate.

Animals↗
PubMed1986

Entorhinal lesions result in increased nerve growth factor-like growth-promoting activity in medium conditioned by hippocampal slices.

Nerve growth factor (NGF) is present in high concentrations in the rat hippocampal formation where it may be involved in sympathetic sprouting following septohippocampal denervation. In addition, recent evidence suggests that some forebrain cholinergic neurons, including septohippocampal neurons, are responsive to exogenous NGF. Since septohippocampal neurons have been shown to sprout in response to entorhinal lesions both in rats and, recently, in humans, we sought to determine whether endogenous NGF-like activity increases in the rat hippocampal formation following injury to the entorhinal cortex. We found that entorhinal lesions which result in extensive denervation of the dentate granule cells, and subsequent sprouting of septohippocampal axons, do result in greater NGF-like growth-promoting activity in medium conditioned by slices of the denervated tissue when compared to medium conditioned by control tissue. These results suggest that brain NGF may be involved in injury-induced sprouting of forebrain cholinergic neurons.

Acetylcholinesterase↗
PubMed1993

Restoration of mnemonic function in rats with glutamergic temporal systems disrupted: dose and time of glycine injections.

Disruption of the connections between the temporal cortex (TC) and lateral entorhinal cortex (LEC) in rats causes impaired memory accompanied by decreased levels of glutamate in these neocortical areas. Administration of glutamergic agonists to rats with TC/LEC disruptions improves retroactive memory. The purpose of this study was to test effects of glycine on proactive memory. The results show that a relatively large dose of glycine (750 mg/kg) injected just prior to training enhanced both acquisition and retention of a discrimination task in TC/LEC rats. Glycine given 1 day prior to training impaired the initial phase of acquisition but improved retention (Experiment 1). Injection of glycine immediately following training or just prior to retrieval reinstated normal mnemonic function in TC/LEC animals, whereas glycine given midway between learning and retention had no such effect (Experiment 2). A potential mnemonic model function of TC/LEC lesion is suggested, and possible beneficial effects of glycine on patients with Alzheimer's disease are discussed.

Animals↗
PubMed1992

Selective lesions in the temporal-hippocampal region of the rat: effects on acquisition and retention of a visual discrimination task.

The first purpose of this study was to investigate whether lesions in the temporal region may affect acquisition or retention of a discrimination task. In Experiment 1, rats with lesions of the temporal cortex (TC), the lateral entorhinal cortex (LEC), or their interconnections were tested postoperatively in simultaneous brightness discrimination. The results show that neither TC lesions nor LEC lesions affected acquisition of the task, and only LEC lesions impaired retention. TC/LEC transections impaired both acquisition and retention. The second purpose was to investigate effects of hippocampal lesions and perforant path transections on the discrimination task (Experiment 2). Both hippocampal and perforant path lesions impaired acquisition of the task, whereas retention was unaffected. It is suggested that TC and LEC are primarily involved in information storing and that hippocampal function is primarily involved in information processing.

Animals↗
PubMed2000

An autoradiographic study of [3H]AMPA receptor binding and in situ hybridization of AMPA sensitive glutamate receptor A (GluR-A) subunits following morphine withdrawal in the rat brain.

Chronic treatment with opioids is well known to result in the development of physical dependence. More recently, glutamatergic mechanisms have been implicated in expression of the withdrawal syndrome from opioids. To better examine glutamatergic involvement, an autoradiographic study of [3H]AMPA receptor binding and an assessment of in situ hybridization of AMPA sensitive glutamate receptor A (GluR-A) subunits in the rat brain were each performed 7 h after withdrawal from morphine infusion. Animals were rendered dependent by intracerebroventricular (i.c.v.) infusion of morphine (26 nmol/microl/h) via osmotic minipumps for 3 days. Brain sections of 14-microm thickness were incubated with 15 nM [3H]AMPA for quantitation of binding to the AMPA receptor. The probe for in situ hybridization was labeled at its 3' end using terminal deoxynucleotidyl transferase and [35S]dATP. The highest degree of [3H]AMPA binding was shown in the hippocampus. The extent of [3H]AMPA binding was increased significantly in the cortex areas (18-21%), caudate-putamen (20%), and hippocampus (7-9%) of rats following withdrawal from morphine. The highest levels of mRNA for GluR-A, flop and flip subunits, were found in the dentate gyrus and in the CA3 region of the hippocampus, respectively. The levels of mRNA for the flop form of GluR-A were decreased in the CA3 of hippocampus (8%) of the rat brain. The levels of mRNA for the flip form of GluR-A were increased in the parietal cortex (7%) and the entorhinal cortex (8%). Increases in the binding of [3H]AMPA to its receptor may play an important role during withdrawal from morphine dependence.

Animals↗
PubMed1999

Odor-induced fast waves in the dentate gyrus depend on a pathway through posterior cerebral cortex: effects of limbic lesions and trimethyltin.

Previous research has shown that the odor of a variety of organic solvents and of components of the anal scent gland excretions of various predators will elicit a burst of fast waves of about 20 Hz in the olfactory bulb, pyriform cortex, and dentate gyrus of the rat. The present experiments show that large lesions of the caudal cerebral cortex, involving particularly the entorhinal and subicular cortices and the angular bundle, abolish the olfactory fast wave response of the dentate gyrus, but not the similar response of the olfactory bulb. In confirmation of previous work, such a lesion also abolishes an average evoked response elicited in the dentate gyrus by electrical stimulation of the olfactory bulb. Systemic treatment with the neurotoxin trimethyltin abolished the olfactory fast wave response in the olfactory bulb and both the olfactory fast wave and the olfactory evoked potential in the dentate gyrus. Large lesions of the amygdala or the septal nuclei did not eliminate either the dentate olfactory evoked potential or the odor-induced dentate fast wave response. However, the septal lesion reduced the amplitude of both spontaneous and odor-induced dentate fast wave activity. It is suggested that olfactory stimuli elicit 20 Hz dentate fast waves via a pathway from the olfactory bulb through the entorhinal cortex and, further, that cholinergic interneurons in the dentate gyrus may be essential to the dentate fast wave response.

Amygdala↗
PubMed1994

Differential expression of Fos protein in the brain of female mice dependent on pup sensory cues and maternal experience.

Immunoreactivity for Fos protein following 30 min of sensory and behavioral experience with foster pups was measured in different brain areas of nulliparous female Balb/c mice who were intact, ovariectomized, or selectively depleted of olfactory bulb noradrenaline. Fos expression was also investigated in intact nulliparous female mice undergoing distal exposure to pup sensory cues. Behavioral interaction with pups increased Fos immunoreactivity in the olfactory areas (anterior olfactory nucleus, piriform cortex, corticomedial amygdala, and entorhinal cortex) as well as in the medial preoptic area, and this occurred regardless of whether females were intact or ovariectomized. Noradrenaline depletion of the olfactory bulb prevented Fos induction in primary olfactory areas, but not in the medial preoptic area, whereas distal exposure to pup cues enhanced Fos expression in the olfactory areas but not in the medial preoptic area.

Amygdala↗
PubMed2001

Regulation of 5-HT(1A) receptor-stimulated [35S]-GtpgammaS binding as measured by quantitative autoradiography following chronic agonist administration.

1. Because changes 5-HT(1A) receptor number do not occur following repeated agonist treatment, we hypothesized that the basis for 5-HT(1A) receptor desensitization involves changes in receptor-G protein coupling. We measured the effect of repeated agonist administration on 5-HT(1A) receptor-stimulated [(35)S]-GTPgammaS binding in forebrain areas, (i.e. anterior cingulate cortex, lateral septum, hippocampus, entorhinal cortex), and serotonergic cell body areas, the dorsal and median raphe nuclei. 2. Following treatment of rats with (+/-)8-OH-DPAT (1 mg kg(-1), s.c.) for 7 or 14 days, 5-HT(1A) receptor-stimulated [(35)S]-GTPgammaS binding was significantly attenuated in both the dorsal and median raphe nuclei. 3. 5-HT(1A) receptor-stimulated [(35)S]-GTPgammaS binding was significantly attenuated in the CA(1) region of the hippocampus after 7, but not 14 days of 8-OH-DPAT administration. 5-HT(1A) receptor-stimulated [(35)S]-GTPgammaS binding was not altered in other forebrain areas examined. 4. The binding of [(3)H]-MPPF to 5-HT(1A) receptor sites was not altered in any brain region examined following repeated agonist administration, suggesting that the observed changes in (+/-)8-OH-DPAT-stimulated [(35)S]-GTPgammaS binding were not due to changes in 5-HT(1A) receptor number. 5. Our data indicate that in serotonergic cell body areas the regulation of presynaptic 5-HT(1A) receptor function following repeated agonist administration occurs at the level of receptor-G protein interaction. In forebrain areas, however, the regulation of postsynaptic 5-HT(1A) receptor sensitivity appears not to be at the level of receptor-G protein coupling.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed2003

A challenge to chaotic itinerancy from brain dynamics.

Brain hermeneutics and chaotic itinerancy proposed by Tsuda are attractive characterizations of perceptual dynamics in the mammalian olfactory system. This theory proposes that perception occurs at the interface between itinerant neural representation and interaction with the environment. Quantifiable application of these dynamics has been hampered by the lack of definable history and action processes which characterize the changes induced by behavioral state, attention, and learning. Local field potentials measured from several brain areas were used to characterize dynamic activity patterns for their use as representations of history and action processes. The signals were recorded from olfactory areas (olfactory bulb, OB, and pyriform cortex) and hippocampal areas (entorhinal cortex and dentate gyrus, DG) in the brains of rats. During odor-guided behavior the system shows dynamics at three temporal scales. Short time-scale changes are system-wide and can occur in the space of a single sniff. They are predictable, associated with learned shifts in behavioral state and occur periodically on the scale of the intertrial interval. These changes occupy the theta (2-12 Hz), beta (15-30 Hz), and gamma (40-100 Hz) frequency bands within and between all areas. Medium time-scale changes occur relatively unpredictably, manifesting in these data as alterations in connection strength between the OB and DG. These changes are strongly correlated with performance in associated trial blocks (5-10 min) and may be due to fluctuations in attention, mood, or amount of reward received. Long time-scale changes are likely related to learning or decline due to aging or disease. These may be modeled as slow monotonic processes that occur within or across days or even weeks or years. The folding of different time scales is proposed as a mechanism for chaotic itinerancy, represented by dynamic processes instead of static connection strengths. Thus, the individual maintains continuity of experience within the stability of fast periodic and slow monotonic processes, while medium scale events alter experience and performance dramatically but temporarily. These processes together with as yet to be determined action effects from motor system feedback are proposed as an instantiation of brain hermeneutics and chaotic itinerancy.

Animals↗
PubMed1987

Long-term neuropathological and neurochemical effects of nucleus basalis lesions in the rat.

The long-term effects of excitotoxic lesions in the nucleus basalis magnocellularis of the rat were found to mimic several neuropathological and chemical changes associated with Alzheimer's disease. Neuritic plaque-like structures, neurofibrillary changes, and neuronal atrophy or loss were observed in the frontoparietal cortex, hippocampus, amygdala, and entorhinal cortex 14 months after the lesions were made. Cholinergic markers in neocortex were reduced, while catecholamine and indoleamine metabolism was largely unaffected at this time. Bilateral lesions of the nucleus basalis magnocellularis increased somatostatin and neuropeptide Y in the cortex of the rat by at least 138 and 284 percent, respectively, suggesting a functional interaction between cholinergic and peptidergic neurons that may differ from that in Alzheimer's disease.

Acetylcholinesterase↗
PubMed1988

Seizures induce dramatic and distinctly different changes in enkephalin, dynorphin, and CCK immunoreactivities in mouse hippocampal mossy fibers.

Light microscopic immunocytochemical techniques were used to evaluate the influence of recurrent limbic seizure activity on the immunoreactivity for 3 neuropeptides--enkephalin, dynorphin, and cholecystokinin (CCK)--contained within the mouse hippocampal mossy fiber axonal system. Seizures were induced either by the placement of a small unilateral electrolytic lesion in the dentate gyrus hilus or by intraventricular injection of kainic acid. Both treatments induce epileptiform activity in hippocampus lasting several hours. Four days after either lesion placement or injection of 0.05-0.1 microgram kainic acid, immunoreactivity for all 3 peptides was altered throughout the intact mossy fiber system, bilaterally, but in distinctly different ways: enkephalin immunoreactivity (ENK-I) was dramatically elevated, dynorphin immunoreactivity was reduced, and CCK immunoreactivity (CCK-I) was either severely reduced or completely absent in the mossy fiber system. ENK-I was also clearly increased in other areas, including the lateral septum, the entorhinal cortex, and within the entorhinal (perforant path) efferents to temporal hippocampus. In contrast, the loss of CCK seemed restricted to the mossy fiber system in that immunostaining appeared normal in scattered hippocampal perikarya, within the dentate gyrus commissural system, as well as within other limbic structures. Four days after injections of 0.2 or 0.25 microgram kainic acid, mossy fiber ENK-I was greatly elevated, dynorphin immunoreactivity was reduced, but, unlike the situation with lower kainic acid doses, CCK-I was only modestly reduced in the mossy fibers and was clearly reduced in other hippocampal systems as well. These data indicate that epileptiform physiological activity differentially affects the regulation of 3 neuroactive peptides contained within the hippocampal mossy fiber system and suggest a mechanism through which seizurelike episodes can have a lasting influence on the operation of specific hippocampal circuitries.

Animals↗
PubMed1995

Morphological evidence for the sprouting of inhibitory commissural fibers in response to the lesion of the excitatory entorhinal input to the rat dentate gyrus.

Recently a commissural fiber projection that terminates in the outer molecular layer of the fascia dentata was described in normal rats (Deller et al., 1995). In the present article, Phaseolus vulgaris leucoagglutinin (PHAL) tracing was used to analyze the contribution of this previously unknown projection to the commissural sprouting response after entorhinal cortex lesion. Rats 4-8 weeks after unilateral entorhinal lesion received a single PHAL deposit into the hilus of the fascia dentata contralateral to the lesion side. Unlesioned control animals received a similar PHAL deposit. The degree of axonal arborization and the bouton density per axon length were determined for individual PHAL-labeled commissural axons to the outer molecular layer of the dentate gyrus. A significant increase in both parameters was observed in the lesioned group. The PHAL-labeled commissural fibers established symmetric synapses in the denervated outer molecular layer. Postembedding immunocytochemistry indicated that some of these sprouting commissural fibers are GABAergic. Our findings provide morphological evidence for lamina-specific sprouting of an inhibitory commissural projection that normally terminates in the outer molecular layer. This suggests that inhibitory fibers participate in the replacement of the excitatory perforant pathway after entorhinal lesion.

Afferent Pathways↗
PubMed1994

[C-fos expression in rat brain during seizure and electroacupuncture].

C-fos proteins were visualized immunohistochemically in the brain of rats after seizures induced by injecting penicillin into hippocampus and by penicillin+electroacupuncture treatment. Three hours following seizures there was an evident expression of c-fos proteins in the hippocampus (CA1 area), dentate gyrus, piriform cortex, dorsal part of entorhinal cortex, and amygdaloid nucleus, and there was a dramatic increase of c-fos proteins in CA3 area and the areas mentioned above except the CA1 area where c-fos proteins apparently decreased after electroacupuncture treatment. The results showed that seizures can induce c-fos proteins in some nuclei related with seizure and that electroacupuncture can also regulates the c-fos expression after seizure.

Animals↗