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H J Gabriel

Publications and source records attributed to H J Gabriel.

At least 19 recordsLinked to original sources
PubMed1999

Intrinsic optical signal measurements reveal characteristic features during different forms of spontaneous neuronal hyperactivity associated with ECS shrinkage in vitro.

We induced three different forms of spontaneous synchronous hyperactivity in adult rat hippocampal-entorhinal cortex slices in order to investigate effects on the intrinsic optical signal and associated changes in the extracellular space (ECS) volume. Low-Mg2+ artificial cerebrospinal fluid (ACSF) and the addition of 4-aminopyridine induced synchronous hyperactivity resulting mainly from increased synaptic transmission, while low-Ca2+ ACSF induced hyperactivity in the absence of evoked synaptic transmission. In the two models of enhanced synaptic transmission, spontaneous activity lead to an immediate increase of light transmission. In contrast, a decrease of light transmission took place during low-Ca2+-induced hyperactivity. All three forms of synchronous neuronal hyperactivity were associated with a shrinkage of the ECS volume, as revealed by the tetraethylammonium signal, measured with ion-sensitive microelectrodes. This indicates that the change in the intrinsic optical signal is not simply related to a shrinkage in ECS volume. We conclude that different forms of spontaneous synchronous neuronal hyperactivity are associated with characteristic optical signals and that the direction of the change in intrinsic optical signal does not reflect ECS shrinkage alone.

4-Aminopyridine↗
PubMed1996

Effects of cholecystokinin on Y, X, and W cells in the dorsal lateral geniculate nucleus of rats.

The role of the cholecystokinergic input to the rat's dorsal lateral geniculate nucleus (dLGN) was studied by examining the effect of iontophoretically administered CCK-8S on the neuronal response to stimulation of the receptive field center. Peristimulus activity was recorded extracellularly from 108 neurons grouped according to the type of receptive field (OFF, ON, or ON-OFF) and classified with respect to their Y, X, or W properties by means of discriminant analysis. CCK affected the response to a center-sized spot of light in two thirds of the neurons investigated. The center response decreased in 50 of 73 CCK-sensitive neurons (69%), predominantly in Y OFF and X OFF center cells (17 of 19). In the remaining 23 cells the center response increased, most consistently (11 of 17) in W ON center cells. Center and surround responses were similarly influenced. Inhibitions and excitations induced by CCK-8S were reproducible, dose dependent, and receptor mediated. The CCKB antagonist PD 135158 reduced the CCK effects in 10 of 14 cells; the CCKA antagonist KL 1001 reduced the CCK effects in 17 of 36 cells. The CCK-induced inhibition was B-receptor specific in 4 of 8 cells, A-receptor specific in 2 of 8 cells, and partially mediated by each of the two types of receptor in the remaining 2 cells. Blocking by the CCKA antagonist was more frequently observed in W cells than in cells with Y or X characteristics. The data show that CCK modifies the activity of dLGN cells in a variable direction depending on the specific cell type (Y, X, W) and response pattern (OFF, ON). The effects of CCK are discussed in relation to proposed functions of the superior collicular input to the dLGN.

Animals↗
PubMed1996

Interaction of cholecystokinin and glutamate agonists within the dLGN, the dentate gyrus, and the hippocampus.

The interaction of sulfated cholecystokinin (CCK-8S) with excitatory amino acids (EAA) was studied on single units of the dorsal lateral geniculate nucleus (dLGN), the dentate gyrus, and the hippocampal CA3 region in rats anaesthetized with urethane. lontophoretic co-administration of small, individually ineffective currents of CCK-8S and kainic acid or N-methyl-D-aspartate repeatedly elicited an increase of the discharge rate in nearly all geniculate and half of the dentate neurons but not in those of the CA3 region. The effect could be reduced by the CCKB receptor antagonist PD 135,158 more often than by the CCKA antagonist KL 1001. The increased firing due to co-administration of CCK and kainate could also be suppressed by the non-NMDA antagonist CNQX but not by the NMDA antagonists CPP or AP-5, which were otherwise able to prevent the neuron from responding to co-administration of CCK and NMDA. It is suggested that in distinct brain regions the effectivity of the "low level" EAA transmission may be enhanced by small amounts of CCK-8S. This is thought to be mediated by a coactivation of CCK and EEA receptors.

Animals↗
PubMed1995

Cholecystokinin excites neostriatal neurons in rats via CCKA or CCKB receptors.

The effect of iontophoretically applied cholecystokinin (CCK) on neurons of the neostriatum was studied in rats anaesthetized with urethane. The most frequently observed effect of the sulphated octapeptide (CCK-8S) on striatal neurons was excitation. Spontaneously active neurons responded more often to CCK-8S than quiescent cells. Silent, primarily non-responsive neurons could often be stimulated with CCK-8S using glutamate to induce an ongoing discharge. Thus, 45.8% of the 177 neurons studied changed their discharge rate by more than 30%. Certain CCK receptor antagonists could prevent the effect of CCK-8S, fully or at least partly, in the majority of CCK-responsive neurons. The data suggest that cholecystokinin modulates the firing of active neostriatal neurons via the CCKA or the CCKB receptor type. Furthermore, we compared neuronal responses to glutamate with those recorded during concomitant administration of CCK-8S in order to study the interaction of both transmitters, which may be colocalized in striatal afferents. CCK-8S mainly enhanced the excitatory effect of glutamate on striatal neurons, but in several neurons the response to glutamate was reduced. The CCKB receptor antagonist could prevent CCK-8S from increasing the glutamate-induced activation.

Animals↗
PubMed1995

Cholecystokinin affects the neuronal discharge mode in the rat lateral geniculate body.

Neurons of the dorsal lateral geniculate body (dLGB) discharge either continuously with single spikes or in bursts, that is, groups of action potentials with an interspike interval < or = 4 ms. The influence of the sulphated octapeptide of cholecystokinin (CCK-8S) on the discharge mode of dLGB neurons was studied in rats anesthetized with urethane. Unit activity was recorded during repeated stimulation with diffuse light. The occurrence of bursts was determined during control conditions and during iontophoretic administration of CCK-8S and its antagonists. CCK-8S frequently increased the number of bursts. The percentage of spikes involved in bursts was mainly augmented in neurons that responded after short latency to light or were excited by light-off. It was predominantly reduced in units responding to light after long latency with a primary excitation. CCKA receptors seem to contribute to burst induction, since CCK-8S reduced bursting in the presence of the CCKA receptor antagonist Ge 410 and increased bursting when applied with the CCKB receptor antagonist PD 135,158. These bursts were frequently related to light stimuli.

Amino Acid Sequence↗
PubMed1994

Cholecystokinin-induced activity changes of dorsal lateral geniculate neurons in rats.

The effects of iontophoretically applied cholecystokinin fragments and cholecystokinin antagonists on neurons of the dorsal lateral geniculate nucleus were investigated with extracellular recordings in rats anesthetized with urethane. The peptide cholecystokinin-8S, which has affinity for both cholecystokinin-A and -B receptors, altered the baseline firing as well as the responses to visual stimuli of about one half of the investigated neurons (90 out of 190). Excitatory effects predominated (P < 0.01, Wilcoxon test), although inhibitory effects were also observed. The effects of cholecystokinin-8S were dose-dependent. Neurons sensitive to cholecystokinin-8S could be found in all regions of the dorsal lateral geniculate nucleus, but they differed in their susceptibility to cholecystokinin in relation to their location. The B-agonist, BOC-cholecystokinin-4, also changed the baseline firing as well as the light-evoked activity of dorsal lateral geniculate nucleus neurons. The effects were either excitatory or inhibitory. Changes induced by cholecystokinin-8S could be effectively blocked by the cholecystokinin-B antagonist, CAM 1028 (19 out of 22 cholecystokinin-sensitive neurons tested). The cholecystokinin-A antagonist, Ge 410, blocked cholecystokinin-induced effects in 10 out of 16 neurons. These results indicate that the modulation of geniculate cell firing by cholecystokinin is mediated by both A-and B-receptor types.

Animals↗
PubMed1993

SLOW and FAST lateral geniculate neurons are differently influenced by acetylcholine.

In rats anesthetized with urethane, potentials of 108 neurons were recorded extracellularly in the dorsal part of the lateral geniculate body (dLGB). Neuronal responses to diffuse light stimuli were studied before and during the iontophoretic application of acetylcholine (ACh). Although individual cells of all groups of functionally different neuron types could be influenced by ACh, responses to flashes were most pronounced and uniformly enhanced in the groups of SLOW ON-like cells located in the dorsolateral and caudal parts of the dLGB. The activity in primary response phases to light flashes increased also in caudally located SLOW OFF-like cells. In the group of ventromedially located FAST OFF-like cells the postinhibitory offdischarge in the response to flash was significantly augmented. Only few cells of FAST ON-like groups were affected and some of them inhibited by ACh. off

Acetylcholine↗
PubMed1991

Regional differences in the control of neuronal transmission in the lateral geniculate nucleus during conditioning in rats.

Responses of neurons of the dorsal part of lateral geniculate nucleus (dLGN) to light were recorded before, during and after termination of pairing with electrical tail stimulation in urethane anesthetized rats. Response changes were induced in about 45% of cells studied during conditioning. These changes persisted in 25% of the cells during the extinction period. Cells which changed their response were mainly located in the caudodorsolateral part of the dLGN. Cells with persistent response modulations are mainly of the slow type. The results are discussed in relation to the known difference of afferentation of the dLGN.

Animals↗
PubMed1990

Conditioning-related changes of unit activity in the dorsal lateral geniculate nucleus of urethane-anaesthetized rats.

Changes in geniculate unit activity of urethane-anaesthetized and freely moving rats were investigated during conditioning. The conditioned stimulus (CS) was a flash which was paired with an electrical stimulation of the tail as unconditioned stimulus (US). The discharge rates evoked by the CS during forward conditioning were significantly higher in responding units than those evoked by reversal of CS and US (backward conditioning) or by pseudoconditioning. Tail stimulation alone did not cause significant changes in the firing rate of most of the neurons. In 25% of the investigated neurons the facilitation of activity evoked by forward conditioning persisted during an extinction period of more than 15 min. The effect of conditioning on neuronal activity appeared to be comparable in urethane-anaesthetized rats and in freely moving ones which responded to the US with a slight freezing behavior.

Anesthesia↗
PubMed1990

Different modulation of flash responses of fast and slow relay cells by aversive electrical brain stimulation.

Electrical activity of single neurons of the dorsal lateral geniculate nucleus of rats was recorded from stereotactically fixed animals. The neurons were classified as fast or slow ones, according to their response latency to electrical stimulation of the chiasma opticum. After this, the responses to diffuse flashes, to aversive electrical stimulation of the brain (ESB) and to a combination of both, brain stimulation immediately followed by a flash, were recorded. One week prior to testing, bipolar nichrom electrodes had been implanted into the tectotegmental region for the ESB, and their effectiveness was tested behaviorally. Out of 78 neurons 56 fast and 22 slow ones were found. Fast neurons have a significantly higher background activity than slow neurons. Both classes show a modulation of flash evoked responses by the ESB, although the ESB has nearly no effect on the spontaneous discharge frequency in any of the neurons. The influence on the flash response differs according to the cell class: the class of fast neurons is predominantly facilitated up to 1100 ms after the flash application, whereas the class of slow neurons is inhibited during this period. Later on (up to 2260 ms after flash) fast cells show no clear net effect, and slow cells were still slightly inhibited.

Animals↗
PubMed1987

Classification of geniculo-cortical relay cells of albino rat dorsal lateral geniculate nucleus by means of multivariate analysis.

It was tested if responses of geniculo-cortical relay (GCR-) cells in rat dorsal lateral geniculate nucleus (dLGN) to diffuse light flashes contain features permitting a separation of the cell population into slow and fast cells like the response latency to stimulation of optic chiasm (OX-latency). The location of neurons within the dLGN found additional consideration. Using hierarchical cluster analysis two clusters were obtained for on- as well as off-like neurons, which reflected to a high degree the classification into slow and fast cells by OX-latency. Two subgroups were detected in the cluster of slow cells. Multivariate discriminance analysis made it possible to separate the cell population into two classes. The latency of primary excitation to flash (primary inhibition for off-cells), the number of impulses in the first excitation peak (duration of inhibitory period) and the location of the cells within the dLGN were suited for this separation differing in 11 up to 17% from that achieved by OX-latency classification.

Animals↗
PubMed1986

Influence of atropine microinjection into nucleus reticularis thalami on activity of lateral geniculate nucleus neurones in freely moving rats.

The influence of the microinjection of atropine into the visual part of the nucleus reticularis thalami (TR) on flash-evoked unit responses of the dorsal lateral geniculate nucleus (dLGN) was investigated in freely moving rats. Atropine induced a significant prolongation and accentuation of the postexcitatory inhibitory phases in water-deprived trained rats, to which light flashes acted as conditioned stimuli and initiated a drinking behaviour. In satiated relaxed rats atropine did not change the unit activity significantly. Acetylcholine injected into TR caused a facilitation of the dLGN transmission. Since the decrease of flash-evoked excitatory response phases in thirsty, trained rats as compared to satiated ones could not be blocked by atropine, not all behaviourally dependent changes are mediated by a disinhibitory action of cholinergic fibres on TR.

Animals↗
PubMed1986

Lateral geniculate cells of different channels of the rat's visual pathway: response changes and functional plasticity.

Potentials of single cells of the dorsal lateral geniculate nucleus (dLGN) were recorded extracellularly in albino rats by means of micropipettes filled with trypan blue for iontophoretic marking of tip localization. The cells were grouped concerning their response latencies to photic stimuli, their response patterns, and their localization within the dLGN. It could be shown in a conditioning paradigm that combination of light with electrical tail stimulation resulted in temporary response changes of "fast" OFF-cells which are mainly localized in the rostroventromedial part of dLGN. "Fast" ON-cells had mainly stable response patterns to light. Changes which persisted after the end of tail stimulation trials occurred in "slow" oN- and oFF-cells located in the dorsolateral and caudal part of dLGN.

Acoustic Stimulation↗
PubMed1985

Regional distribution of fast and slow geniculo-cortical relay cells (GCR-cells) within the rat's dorsal lateral geniculate nucleus (LGNd).

Unit activity of 135 GCR-cells in rat's LGNd was recorded extracellularly using micropipettes filled with trypan blue for subsequent marking of recording sites. The latencies of responses to electrical stimulation of the optic chiasma (OX) were mapped, and in accordance with Fukuda (1973) each GCR-cells was classified as fast or slow. Fast cells predominate in the rostroventromedial subregion and slow cells in the caudal part. Both fast and slow subtypes were found in the remaining rostrodorsolateral zone where slow cells made up two thirds of the subsample. The results fit the suggestion that in the LGNd of rats a fast retino-geniculate pathway relays in the ventromedial region, whereas slow pathways exist in the caudal as well as in the dorsolateral zone.

Animals↗
PubMed1985

Distribution of ON- and OFF-cells within the rat dorsal lateral geniculate nucleus.

Neurons responding to light flashes with a primary suppression of activity (OFF-like cells), and those responding with excitation (ON-like) differ significantly in their localization within the rat's dorsal lateral geniculate nucleus (dLGN). ON-cells are aggregated in the dorsolateral part, OFF-cells predominantly in the ventromedial part.

Animals↗
PubMed1984

[The perforated gallbladder in sonography].

The most dangerous complication in cholelithiasis is the perforation of the gallbladder wall. Ultrasound examination of patients with this disease is an easy technique for diagnosis. Four cases of sonographically detected perforation of the gallbladder are reported. Several distinctive sonographic diagnostic patterns depending on the side of perforation have evolved and are described. Suspicion of gallbladder perforation should be considered particularly in elderly patients with cholelithiasis and suddenly evolving pain in the right upper quadrant.

Aged↗
PubMed1982

Lateral geniculate unit activity in freely moving rats. I. Relation to behavior and stimulus relevance.

Using semimicroelectrodes implanted in the dorsal lateral geniculate body unit responses to light stimuli were recorded in two groups of rats in the state of water deprivation and after satiation. The animals of one group were trained to keep still in order to receive water, the others were trained to approach water dispenser on the light stimulation with a water reward. Responses of about two thirds of the units recorded in both groups differ depending on the animals’ behavior or motivational state. Drinking before stimulation had little influence. In spite of a similarity of behavior in both groups there was a significant tendency only in the LT-group, consisting of a prolongation of the postexcitatory suppression periods and an increase of the second excitation in satiated animals vs. water deprived ones. This might be ascribed to processes connected with the biological meaning of the light stimulus.

Animals↗