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At least 109 records · Page 6Linked to original sources
PubMed1988

Glutamate decarboxylase-immunoreactive neurons in the aging rat hippocampus are more resistant to ischemia than CA1 pyramidal cells.

Glutamate decarboxylase (GAD)-immunoreactive, supposedly GABAergic inhibitory, neurons in various fields of the rat hippocampus and pyramidal cells in area CA1 were quantified 1 week after transient cerebral ischemia by 4-vessel occlusion. Whereas the number of CA1 pyramidal cells in Toluidine blue-stained semithin sections were found reduced by 50% when compared with controls there was no loss of GAD-immunoreactive cells in vibratome sections of hippocampus proper and fascia dentata. These data suggest that GABAergic hippocampal neurons are more resistant to ischemia than CA1 pyramidal cells.

Aging↗
PubMed1992

5-Hydroxytryptamine increases excitability of CA1 hippocampal pyramidal cells.

In the presence of spiperone to block the 5-HT1A-mediated inhibition of pyramidal cell activity, 5-hydroxytryptamine (serotonin, 5-HT) produces a rapid transient increase in amplitude of the extracellularly recorded population spike from area CA1 of the hippocampus. Intracellular recording techniques in area CA1 of rat hippocampal slices were used to identify the ionic mechanism and to characterize the 5-HT receptor mediating this excitatory response to 5-HT. Most of the experiments were conducted in the presence of spiperone to block the 5HT1A hyperpolarization. Since spiperone also has high affinity for 5-HT2 receptors, any response mediated by 5-HT2 receptors would also be blocked. Bath perfusion of the slice with 5-HT increased the rectification of pyramidal cells in the subthreshold region, increased the resistance, and increased the amplitude of subthreshold excitatory postsynaptic potentials (EPSPs) to initiate spike firing. The 5-HT2,1C-selective agonist DOI mimicked this effect of 5-HT, and the 5-HT2,1C antagonist ketanserin (1 microM) blocked the effect of DOI. There was no change in the amplitude of the slow afterhyperpolarization (sAHP) or the amplitude of evoked inhibitory postsynaptic potentials (IPSPs). The increase in rectification and EPSP amplitude by 5-HT occurred even in the presence of the 5-HT4-selective antagonist BRL 24924 to prevent the decrease in amplitude of the sAHP by 5-HT. We conclude that 5-HT produces a fast excitatory response by increasing subthreshold conductance in CA1 hippocampal pyramidal cells. The identity of the receptor mediating this response was not conclusively identified, but resembled the 5-HT1C receptor.

Action Potentials↗
PubMed1980

Excitatory action of opioid peptides and opiates on cultured hippocampal pyramidal cells.

Bath application of low concentrations of opioid peptides and higher concentrations of opiates increased the amplitude and duration of excitatory postsynaptic potentials of pyramidal cells and induced long-lasting depolarization shifts. These actions were reversible and blocked by the opiate antagonist naloxone. Synaptic isolation of the cells by exposure of the cultures to 8 mM Mg2+ not only abolished all spiking and synaptic activity, but also obliterated the peptide effects on pyramidal cells, although these cells were still excited by bath-applied glutamate. The opioid peptides had no detectable effect on resting membrane potential and on the input resistance of the penetrated cells. Experiments in which pyramidal cells were synaptically activated by field stimulation provided direct evidence for a disinhibitory action of the peptides.

Animals↗
PubMed1986

Hippocampal pyramidal cells and aging in the human: a quantitative study of neuronal loss in sectors CA1 to CA4.

A number of investigators have proposed that hippocampal pathology contributes to the memory impairment seen in normal aging. The published morphometric studies of aging-associated quantitative changes in pyramidal cells in human hippocampus have yielded somewhat inconsistent results. We measured the volume, pyramidal cell density, and neuronal and nuclear cross-sectional areas in sectors CA1 through CA4 in right and left hippocampi from the brains of 23 normal subjects (age range 4 to 98 years) in the Yakovlev Collection. All four hippocampal sectors tended to show a decline in volume and pyramidal cell density with age, but the degree of neuronal loss was statistically significant only in CA4. The aging-related cell loss did not appear to be linear, but was most obvious after age 65. Elderly subjects had 19% (CA1), 16% (CA2), 17% (CA3), and 25% (CA4) lower mean pyramidal cell density compared with subjects under age 65. The relatively greater neuronal loss in CA4 could possibly be related to its high catecholaminergic innervation.

Adolescent↗
PubMed1983

Field-potential evidence for extrasynaptic alterations in the hippocampal CA1 pyramidal cell population during paired-pulse potentiation.

The mechanisms of paired-pulse potentiation of the CA1 pyramidal cell population were examined by determining input-output relations for control and potentiated responses originating from the activation of radiatum fibers in the hippocampal slice preparation. Two types of potentiation for synchronously discharging pyramidal cells (population spike) were observed. In the first type, the potentiation of the population spike was found to be a combination of synaptic and extrasynaptic factors. This form of potentiation was observed in 16 of 28 slices. In the second type, the potentiation of the population spike was attributed entirely to the potentiation of summated dendritic depolarizations (population EPSP). This synaptic process of potentiation was observed in 12 of 28 slices. The involvement of only extrasynaptic mechanisms in the paired-pulse potentiation of the population spike was not observed. For the potentiation originating from a combination of synaptic and extrasynaptic mechanisms, 60% of the potentiation of the population spike was a result of synaptic factors and 40% could be attributed to extrasynaptic factors. These results support the concept that alterations in the excitability of postsynaptic neurons serve as a component of the mechanisms of paired-pulse potentiation in the radiatum fiber-CA1 pyramidal cell system.

Action Potentials↗
PubMed1990

Effects of dopamine, D-1 and D-2 dopaminergic agonists on the excitability of hippocampal CA1 pyramidal cells in guinea pig.

In hippocampal pyramidal cells (HPCs), Dopamine (DA) application (1 microM) produced, in 50% of recorded cells, an hyperpolarization of the resting membrane potential (r.m.p.) and an increase of the afterhyperpolarization (AHP) amplitude and duration in 79% of recorded cells. DA-induced effects on both the r.m.p. and AHP were mimicked by bath application of a D-1 selective agonist, SKF 38393 (20 microM). In addition, we have observed that a D-1 selective antagonist such as SCH 23390 (1 microM) abolished the action of both DA and SKF 38393. In contrast, the activation of D-2 receptors through LY 171555 (10 microns) produced, in 50% of cells, a depolarization of the r.m.p. and a depression of the AHP in 67% of recorded cells. These results suggest that the effects observed in hippocampal pyramidal neurons after DA application of micromolar concentration are mediated by D-1 subtype of receptors.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1976

On the fine structure of the small, heavily pigmented non-pyramidal cells in lamina II and upper lamina III of the human isocortex.

With the aid of a newly developed technique for the successive examination of both the Golgi and pigment picture of individual neurons (Braak, 1974a) Braak (1974b) demonstrated that within lamina II and upper lamina III of the human isocortex, heavily pigmented non-pyramidal cells are distributed irregularly and sparsely. The lipofuscin pigment granules serve as excellent internal markers to identify these non-pyramidal cells in ultrathin sections. This favourable circumstance facilitates the study of these interneurons in the electron microscope. The heavily pigmented non-pyramidal cells are small, spherical to avoid with diameters of about 12-15 mum. One pole of the cell comprising a large cytoplasmic area gives rise to a few dendrites, while the other pole is occupied by the nucleus and in some cases is in close apposition to another nerve cell body. The nucleus is deeply invaginated by the large cytoplasmic area and occasionally displays nuclear inclusions. Among the usual organelles distributed within the large cytoplasmic area the mitochondria with a moderately electron dense matrix are abundant and the coarse lipofuscin pigment granules are the most striking elements. The latter contain densely packed filamentous or tubular material and a single vacuole. The perikaryon rarely receives more than 3 type I and type tii synapses per section per cell, whereas the dendrites receive numerous synapses of both type I and type II. Within the apposition zone to another nerve cell body (which in no case is a heavily pigmented non-pyramidal cell) puncta adhaerentia occur and also contacts in which the cleft of 8 nm is intersected by a dense stratum. Some of the ultrastructural findings are summarized in the schematic drawing of Figure 15.

Adult↗
PubMed1982

The relationship of dendritic branching complexity to ontogeny and cortical connectivity in the pyramidal cells of the monkey amygdala: a Golgi study.

A quantitative analysis of the dendritic branching complexity of pyramidal cells in the small pyramidal celled divisions of the monkey amygdala reveals a systematic variation among the divisions. This variation provides a basis for the identification and differentiation of the divisions in the Golgi impregnated rhesus monkey amygdala. The order of increasing dendritic branching complexity of the divisions under consideration is as follows: cortical nucleus, medial basal nucleus, parvocellular accessory basal nucleus and ventromedial portion of lateral nucleus, and dorsolateral portion of the lateral nucleus. The order of these divisions in terms of their dendritic branching complexity bears a direct relationship to their ontogenetic developmental sequence and to their progressive transition in connectivity from allocortical to more highly evolved isocortical input.

Amygdala↗
PubMed1988

Responses of hippocampal pyramidal cells to putative serotonin 5-HT1A and 5-HT1B agonists: a comparative study with dorsal raphe neurons.

In low cerveau isolé transected rats, the effects of microiontophoretic application of putative serotonin 5-HT1A and 5-HT1B agonists on the spontaneous firing rate of CA1 pyramidal cells were compared to those of 5-HT. In contrast to the large current-dependent suppression of unit activity observed with 5-HT, the 5-HT1A compounds, ipsapirone, 8-OH-DPAT (8-hydroxy-2-(di-n-propylamino)-tetralin) and LY 165163 (p-aminophenylethyl-m-trifluoromethylphenylpiperazine) and the 5-HT1B compounds, mCPP (m-chlorophenylpiperazine) and TFMPP (trifluoromethylphenylpiperazine), produced only weak inhibition of spontaneous firing. Conversely, using identical ejection parameters, ipsapirone and LY 165163 (previously reported) and 8-OH-DPAT were as effective as 5-HT in inhibiting markedly the baseline activity of serotonergic dorsal raphe neurons; mCPP and TFMPP (previously reported) were only weakly active. In view of the minor suppressant effects of the 5-HT1A agonists on the firing of pyramidal cells, a modulatory role for these compounds was sought. Excitation of pyrimadal cells, induced by microiontophoretic application of glutamate, was attenuated by ipsapirone and 8-OH-DPAT; however, when directly compared in the same cells, ipsapirone was no more effective than the 5-HT1B agonist, mCPP. In summary, the inability of CA1 pyramidal cells to distinguish the actions of 5-HT1A and 5-HT1B ligands is in sharp contrast to the striking differences observed for these compounds with dorsal raphe neurons. Consistent with these findings is the idea that 5-HT1A compounds are full agonists on dorsal raphe neurons but only partial agonists on pyramidal cells.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1985

On layer III pyramidal cells in the parastriate borderzone of man.

The parastriate borderzone in the human occipital cortex is made conspicuous by clusters of large pyramidal cells in layer III (limen parastriatus gigantopyramidalis: von Economo and Koskinas 1925). Experiments in higher primates provide evidence that the vertical meridian is represented in this region and that these large pyramidal cells connect the parastriate borderzone of both hemispheres via callosal fibres. Golgi preparations of the human parastriate borderzone reveal that the large pyramidal cells generate a stout apical dendrite which gives rise to several side branches in layer III and terminal ramifications in layer II. An unusual feature is that the apical dendrite is almost devoid of spines and that its side branches are only sparsely spined as well. Both the basal and lateral portions of the cell body give rise to spiny dendrites having their domain within layers III and IV. In pigment-Nissl preparations, the large layer III pyramids are marked by coarse and distinct Nissl bodies and a bowel-shaped accumulation of faintly tinged lipofuscin granules located close to the nucleus. Electron micrographs show that up to 30% of the soma membrane are covered by large boutons which make multiple synaptic contacts. This contrasts to the appearance of most other types of cortical pyramydal cells which normally show only a few axo-somatic contacts.

Adult↗
PubMed1987

Hippocampal pyramidal cell orientation in schizophrenia. A controlled neurohistologic study of the Yakovlev collection.

The finding of marked disorganization of the hippocampal pyramidal cell layer in the brains of schizophrenic patients has recently been reported. The present study was undertaken to determine whether similar abnormalities could be found in the brains of a population of schizophrenic patients, most of whom were never exposed to neuroleptics. Though statistical analysis of 2808 pyramidal cells failed to reveal significantly greater disorganization in a group of seven alleged schizophrenic brains than in brains of age-matched, nonpsychotic controls, the data suggest a relationship between the degree of pyramidal cell disarray and the severity of behavioral impairment due to psychosis. The implications and pitfalls in interpreting these findings are discussed.

Adult↗
PubMed1984

Voltage-clamp study on GABA response desensitization in single pyramidal cells dissociated from the hippocampus of adult guinea pigs.

Acutely dissociated pyramidal cells prepared from the hippocampus of adult guinea pigs were used for the present study. The characteristic dual response of pyramidal cells to GABA as demonstrated in the in vivo and slice preparations was retained in the dissociated cells. The results show that the fading of the GABA hyperpolarizing response during prolonged GABA application cannot be accounted for by the development of an opposing depolarizing response, nor can it be explained by changes in the intracellular ionic composition during GABA action. The data strongly suggest that GABA receptors mediating the hyperpolarizing response exhibit desensitization and the time course of the GABA response is significantly controlled by this property of the receptors.

Animals↗
PubMed1989

Chronic estrogen effects on 5-hydroxytryptamine-mediated responses in hippocampal pyramidal cells of female rats.

Intracellular recording techniques were used to assess the effect of chronic estrogen treatment of ovariectomized (OVX) rats on CA1 pyramidal cell properties and serotonin (5-HT)-mediated responses in the dorsal hippocampus. The magnitude of the 5-HT1A-mediated hyperpolarization and concomitant change in membrane resistance elicited by 15 microM 5-HT was greater in pyramidal cells from OVX rats treated with estrogen (OVX + ES) than in pyramidal cells from OVX rats. Estrogen treatment did not alter the cellular membrane properties or the reduction in AHP amplitude elicited by 15 microM 5-HT. The modulation of 5-HT neurotransmission by estrogen may contribute to variations in mood which are associated with the menstrual cycle.

Animals↗
PubMed1991

Non-pyramidal cells in the CA3 region of the rat hippocampus: relationships of fine structure, synaptic input and chemical characteristics.

The non-pyramidal cells of the hippocampus are heterogeneous with respect to their morphology, peptide content, physiological properties, and postsynaptic targets. Here we demonstrate that the content of peptides (cholecystokinin, somatostatin) and calcium-binding proteins (parvalbumin and calbindin) of non-pyramidal cells is not related to a characteristic fine structure or synaptic input. Varying numbers of GABA-negative and GABA-positive input synapses of non-pyramidal cells indicate that these neurons are differently integrated in inhibitory and disinhibitory circuits.

Animals↗
PubMed1981

Electrotonic coupling between pyramidal cells: a direct demonstration in rat hippocampal slices.

Intracellular recordings from pairs of neurons in slices of rat hippocampus directly demonstrated electronic coupling between CA3 pyramidal cells. When two neurons were impaled simultaneously (as verified by subsequent double staining with horseradish peroxidase), current pulses injected into one cell caused voltage changes in other cells. These interactions were bidirectional. Fast prepotentials, historically thought to represent spike activity in dendrites, resulted from action potentials in other electronically coupled pyramidal cells. These data directly demonstrate electrotonic coupling between neurons in the mammalian brain and indicate that some fast prepotentials are coupling potentials. Coupling between pyramidal cells could mediate synchronization of normal rhythmic activity and of burst discharges during seizures.

Action Potentials↗
PubMed1990

Gonadal steroids regulate dendritic spine density in hippocampal pyramidal cells in adulthood.

Gonadal steroids are known to influence hippocampal physiology in adulthood. It is presently unknown whether gonadal steroids influence the morphology of hippocampal neurons in the adult intact rat brain. In order to determine whether female sex hormones influence hippocampal morphology in the intact adult, we performed Golgi impregnation on brains from ovariectomized rats and ovariectomized rats which received estradiol or estradiol and progesterone replacement. Removal of circulating gonadal steroids by ovariectomy of adult female rats resulted in a profound decrease in dendritic spine density in CA1 pyramidal cells of the hippocampus. Estradiol replacement prevented the observed decrease in dendritic spine density; progesterone augmented the effect of estradiol within a short time period (5 hr). Ovariectomy or gonadal steroid replacement did not affect spine density of CA3 pyramidal cells or granule cells of the dentate gyrus. These results demonstrate that gonadal steroids are necessary for the maintenance of normal adult CA1 hippocampal pyramidal cell structure. The short time course required to observe these effects (3 d for the estradiol effect and 5 hr for the progesterone effect) implies that CA1 pyramidal cell dendritic spine density may fluctuate during the normal (4-5 d) rat estrous cycle.

Animals↗
PubMed1984

Penicillin-induced epileptogenesis in immature rat CA3 hippocampal pyramidal cells.

Penicillin's ability to produce epileptiform discharges in the CA3 region of hippocampus was examined both extracellularly and intracellularly in slices taken from immature rats 3-25 days of age. Comparisons were made to similar recordings from slices taken from mature rats. Between postnatal days 9 and 19 penicillin treatment resulted in spontaneous extracellular epileptiform bursts and coincident intracellular depolarization shifts. These events were more prolonged and less frequent than in slices from mature rats, and the bursts were followed by prolonged afterdischarges, often 20-30 s in duration. Intracellularly these afterdischarges consisted of large, rhythmic slow depolarizing potentials, which resulted in one or more action potentials in individual CA3 pyramidal cells. Extracellular field recordings showed these events to be simultaneous with synchronous discharges of a large population of CA3 pyramidal cells. In pups 1-2 weeks of age the ability of hippocampus to produce prolonged afterdischarges was associated with a slow depolarizing afterpotential, which followed the downstroke of the depolarization shift. Coincident with this afterpotential was a prolonged negative field in the CA3 pyramidal cell body layer. By postnatal days 24 and 25 the tendency to generate afterdischarges was greatly reduced. In addition, afterdischarges were observed infrequently in slices taken during the first postnatal week. Spike trains produced by prolonged intracellular current injection in slices taken on postnatal days 9-19 were followed by large afterhyperpolarizations and were unable to produce afterdischarges in individual CA3 pyramidal cells. Intracellular recordings from presumed glial cells suggest that extracellular K+ accumulation may play a role in the pronounced capacity of hippocampus from 1- and 2-week-old rat pups to generate prolonged afterdischarges.

Age Factors↗
PubMed1991

Endogenous opioids released from perforant path modulate norepinephrine actions and inhibitory postsynaptic potentials in guinea pig CA3 pyramidal cells.

The stimulus parameters needed for the release of endogenous opioid peptides were investigated using an in vitro radioligand displacement assay in living guinea pig hippocampal slices. Electrical stimulation of the enkephalin-containing fibers in the perforant path caused the release of endogenous opioid peptides and the subsequent displacement of [3H]-[D-Ala2,N-methyl-Phe4,glyol5]enkephalin binding. High frequency trains of stimuli (10 Hz for 1 sec every 10 sec) were more effective than lower frequency stimulation (1 Hz continuous) at evoking opioid peptide release. Having identified an effective stimulation paradigm able to release endogenous opioids, the electrophysiological effects of endogenous opioids on CA3 pyramidal cells were measured in the guinea pig hippocampal slice preparation. Unlike exogenously applied opioids, stimulated release of endogenous opioid peptides from the perforant path did not significantly reduce inhibitory postsynaptic potential (IPSP) amplitudes recorded in CA3 pyramidal cells. However, perforant path stimulation in the presence of naloxone did cause a dramatic increase in IPSP amplitudes. CA3 pyramidal cells were not directly affected by perforant path stimulation. The naloxone-sensitive increase in IPSPs was delayed 3 min in onset and lasted for several minutes. In addition, the increase in the IPSPs was specifically blocked either by the beta adrenergic antagonist propranolol or by pretreating the animals with reserpine. These findings indicate that endogenous opioids regulate the effects of norepinephrine in the CA3 region of the guinea pig hippocampus. In addition, endogenously released norepinephrine appeared to act on GABAergic interneurons to increase the amplitude of the IPSP recorded in CA3 pyramidal cells.

Animals↗