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B Kocsis

Publications and source records attributed to B Kocsis.

At least 55 records · Page 3Linked to original sources
PubMed1996

Midbrain raphe cell firing and hippocampal theta rhythm in urethane-anaesthetized rats.

This study aimed to examine the functional coupling between midbrain raphe and the septohippocampal system at the level of neuronal firing. Raphe unit activity and hippocampal EEG were simultaneously recorded in urethane-anaesthetized rats and their relationship was examined in the frequency domain. Subsets of presumably non-serotonergic neurones in both the dorsal and median raphe nuclei fired rhythmically in synchrony with hippocampal theta activity. Theta cells in the median raphe showed higher coherence than those in dorsal raphe and formed a more homogeneous group of cells, according to their firing rates. Since the raphe-septal serotonergic system is known to desynchronize the hippocampal EEG, activation of a subset of nonserotonergic cells during theta in this nucleus indicates a feedback from the limbic circuitry on the ascending raphe control of forebrain activity.

Anesthesia, General↗
PubMed1996

Medial septal unit firing characteristics following injections of 8-OH-DPAT into the median raphe nucleus.

Extracellular single-unit recording techniques were used to examine the firing characteristics of neurons in the medial septum/diagnol band of Broca complex (MS/DB) following injections of the 5-HT1A agonist, 8-OH-DPAT, into the median raphe nucleus (MRN) of urethane-anesthetized rats. It had previously been shown that MRN injections of 8-OH-DPAT produce hippocampal theta rhythm. Injections of 8-OH-DPAT into the MRN produced a change in firing characteristics of MS/DB neurons from an irregular discharge to a pattern of rhythmical bursting in synchrony with hippocampal theta rhythm. Cross-correlational and coherence analyses demonstrated that the rhythmical firing pattern of MS/DB neurons strongly correlated with rhythmical fluctuations in the hippocampal EEG during periods of hippocampal theta produced by 8-OH-DPAT injections, but not during baseline conditions (i.e. hippocampal desynchronization). The results suggest that MRN control of the hippocampal EEG is modulated by the MS/DB. Serotonergic projections from the MRN to the MS/DB may normally act to inhibit the rhythmical bursting of MS/DB neurons, thereby producing hippocampal desynchronization. Suppression of MRN 5-HT neurons by MRN injections of 8-OH-DPAT would disinhibit MS/DB neurons, allowing them to burst rhythmically and thereby produce hippocampal theta rhythm.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1995

Baroreceptor influence on the relationships between discharges of different sympathetic nerves of the cat.

1. The sympathetic nerve discharge (SND) of three different nerves and the arterial blood pressure (BP) were recorded simultaneously in baroreceptor-intact cats. The linear correlation between different nerve pairs was characterized by the coherence spectrum and its baroreceptor-related component was estimated by partialization of the coherence on the basis of the blood pressure signal. 2. The SND-SND coherence values were higher than those found earlier in baroreceptor-denervated cats. As shown by partial coherence analysis, in about 50% of the experiments with high SND-BP coherence (25 nerve pair recordings), this could be explained by superposition of the effects of common central sources of activity and of the additional common rhythmic input from the baroreceptors. Partialization was ineffective in 50% of the experiments with high SND-BP coherence (22 nerve pairs) and also when the SND-BP coherence was relatively low (17 nerve pairs). On the group average, after elimination of the components explained by baroreceptor influence, the peak SND-SND coherence no longer correlated with the SND-BP coherence and both the numerical values and the relative pattern of coherences between different nerves became similar to those characteristic for baroreceptor-denervated cats. 3. It is suggested that the method used in this study represents a 'theoretical barodenervation' and may be of great value in experiments, when surgical or chemical denervation of the baroreceptors does not represent a real option, e.g. in human subjects.

Animals↗
PubMed1995

Injections of muscimol into the median raphe nucleus produce hippocampal theta rhythm in the urethane anesthetized rat.

It has previously been shown that serotonergic [5-hydroxytryptamine (5-HT)] neurons of the median raphe nucleus (MR) are critically involved in the control of the hippocampal electroencephalogram (EEG). Activation of MR 5-HT neurons desynchronizes the hippocampal EEG, whereas inhibition of MR 5-HT activity produces hippocampal theta rhythm. The MR contains an intrinsic population of gamma-aminobutyric acid (GABA) containing neurons that synapse on 5-HT cells of the MR. The present study examined the effects on the hippocampal EEG of injections of the GABAA agonist muscimol hydrobromide into the MR. Low doses of muscimol (0.5 microgram) produced hippocampal theta rhythm at a mean latency of 6.81 min and for a mean duration of 23.6 min. Higher doses (1.0 microgram and 3.0 micrograms, respectively) produced theta at mean latencies of 2.24 min and 3.2 min and for mean durations of 31.84 min and 24.88 min. Injections of muscimol into regions adjacent to the MR generated theta at significantly longer latencies or were without effect. The present results indicate that MR injections of muscimol produce theta by inhibiting the activity of MR 5-HT neurons. It is concluded that MR GABAergic systems, via their influence on MR 5-HT cells, serve an important role in the control of the hippocampal EEG.

Anesthesia↗
PubMed1995

The supramammillary nucleus: is it necessary for the mediation of hippocampal theta rhythm?

Recent evidence suggests that the supramammillary nucleus of the posterior hypothalamus serves as an important relay in a brainstem to septum/hippocampus pathway involved in the generation of hippocampal theta rhythm. In order to examine the role of the supramammillary nucleus as a possible relay/mediator of hippocampal theta rhythm, electrolytic lesions and procaine injections were administered to the supramammillary nucleus of freely moving and urethane-anesthetized rats, respectively. In the urethane-anesthetized rat, it was found that procaine injections attenuated both the frequency and amplitude of theta rhythm elicited by stimulation of the pontine reticular formation. These data suggest that the pontine reticular elicitation of hippocampal theta rhythm is mediated through connections with the supramammillary nucleus. However, it was found that lesions of the supramammillary nucleus failed to produce significant changes in the hippocampal electroencephalogram of freely moving animals. Several explanations concerning this apparent discrepancy are discussed. The most compelling is that multiple brainstem to septum/hippocampus pathways may serve to generate or facilitate the generation of theta rhythm in the freely moving animal. The present report demonstrates that the supramammillary nucleus plays a questionable role in the mediation of hippocampal electroencephalogram signals which are thought to be important for mnemonic processes.

Animals↗
PubMed1994

Separation of hippocampal theta dipoles by partial coherence analysis in the rat.

In order to separate the effect of different theta generators in the hippocampus and to characterize the pattern of relationships between them, in this study, we calculated the coherence that remains between EEG signals, recorded (1) in the stratum oriens of the CA1 region and (2) close to the hippocampal fissure in the dentate gyrus of the right or left hippocampus, after the variations, common also for a third recording site is eliminated (partialization). We found that in both anesthetized and freely moving rats, there is a selective high correlation (coherence) between theta rhythmic activities of contralateral homonymous sites of the hippocampus. The coherence between field potentials recorded in ipsilateral superficial and deep layers was eliminated when allowance was made for any of the contralateral hippocampal recordings. On the other hand, coherence between contralateral homonymous theta dipoles did not decrease when partialized by a heteronymous hippocampal EEG signal. The present results support earlier findings on multiple hippocampal theta dipoles and indicate that they can be separated using partial coherence analysis. The left and right superficial and deep dipoles oscillate as if they formed two separate systems one extending over the superficial CA1 layers on both sides and the other consisting of the left and right deep hippocampal theta dipoles. The results also suggest an important role of the commissural projections in interhemispheric theta synchronization.

Animals↗
PubMed1994

Injections of excitatory amino acid antagonists into the median raphe nucleus produce hippocampal theta rhythm in the urethane-anesthetized rat.

The median raphe nucleus (MR) exerts a pronounced desynchronizing influence on the hippocampal EEG. MR stimulation disrupts theta, while MR lesions produce constant uninterrupted theta. The MR receives pronounced excitatory amino acid (EAA)-containing afferents that have been implicated in several MR-mediated behaviors. The present study examined the effects on the hippocampal EEG of MR injections of the following EAA antagonists in the urethane-anesthetized rat: 2-amino-7-phosphonoheptanoate (AP-7), dizocilpine maleate (MK-801), and gamma-glutamyl-aminomethylsulfonic acid (GAMS). MR injections of the competitive (AP-7) and non-competitive (MK-801) N-methyl-D-aspartic acid (NMDA) receptor antagonists produced theta at short latencies (2.86 min; 4.02 min, respectively) and for long durations (116.1 min; 66.8 min, respectively). It was further shown that the theta-eliciting effects of AP-7 injections could be reliably and temporarily reversed with MR injections of NMDA. MR injections of the kainate/quisqualate receptor antagonist (GAMS) also produced theta at relatively short latencies (6.5 min) and for long durations (60.5 min) indicating that EAA effects on the MR are not NMDA receptor specific. Injections of each of the foregoing EAA antagonists into regions of the brainstem adjacent to the MR including the dorsal raphe nucleus and the medullary or pontine reticular formation generated theta at very long latencies or were without effect. The present findings indicate EAA afferents to the MR normally exert an excitatory influence on the MR in its desynchronization of the hippocampal EEG, whereas the removal of EAA inputs to MR produces the opposite: a reduction of MR activity and hence the elicitation of theta.(ABSTRACT TRUNCATED AT 250 WORDS)

2-Amino-5-phosphonovalerate↗
PubMed1994

Projections of the dorsal raphe nucleus to the brainstem: PHA-L analysis in the rat.

Early studies that used older tracing techniques reported exceedingly few projections from the dorsal raphe nucleus (DR) to the brainstem. The present report examined DR projections to the brainstem by use of the anterograde anatomical tracer Phaseolus vulgaris leucoagglutinin (PHA-L). DR fibers were found to terminate relatively substantially in several structures of the midbrain, pons, and medulla. The following pontine and midbrain nuclei receive moderate to dense projections from the DR: pontomesencephalic central gray, mesencephalic reticular formation, pedunculopontine tegmental nucleus, medial and lateral parabrachial nuclei, nucleus pontis oralis, nucleus pontis caudalis, locus coeruleus, laterodorsal tegmental nucleus, and raphe nuclei, including the central linear nucleus, median raphe nucleus, and raphe pontis. The following nuclei of the medulla receive moderately dense projections from the DR: nucleus gigantocellularis, nucleus raphe magnus, nucleus raphe obscurus, facial nucleus, nucleus gigantocellularis-pars alpha, and the rostral ventrolateral medullary area. DR fibers project lightly to nucleus cuneiformis, nucleus prepositus hypoglossi, nucleus paragigantocellularis, nucleus reticularis ventralis, and hypoglossal nucleus. Some differences were observed in projections from rostral and caudal parts of the DR. The major difference was that fibers from the rostral DR distribute more widely and heavily than do those from the caudal DR to structures of the medulla, including raphe magnus and obscurus, nucleus gigantocellularis-pars alpha, nucleus paragigantocellularis, facial nucleus, and the rostral ventrolateral medullary area. A role for the dorsal raphe nucleus in several brainstem controlled functions is discussed, including REM sleep and its events, nociception, and sensory motor control.

Animals↗
PubMed1994

Pharmacological suppression of the median raphe nucleus with serotonin1A agonists, 8-OH-DPAT and buspirone, produces hippocampal theta rhythm in the rat.

The effects on the hippocampal electroencephalogram of microinjections of procaine hydrochloride and the serotonin1A agonists, 8-OH-DPAT and buspirone, into the median raphe nucleus were examined in the urethane anesthetized rat. Injections of procaine, 8-OH-DPAT or buspirone into the median raphe nucleus produced a change in the hippocampal electroencephalogram from a spontaneous desynchronized pattern to a synchronized pattern (theta rhythm) within short latencies and for long durations post-injection. Procaine was shown to elicit theta at a mean latency of 52 s and for a mean duration of 21.75 min; buspirone at a mean latency of 2 min and for a mean duration of 34.5 min. A dose dependent relationship was observed between 8-OH-DPAT injections and latencies but not durations. Small doses (0.5 micrograms) of 8-OH-DPAT produced theta at a mean latency of 1.33 min and large doses (3.0 micrograms) at a mean latency of 1.17 min. 8-OH-DPAT injections generated theta for a mean duration of 62 min. Injections of each of these substances into structures dorsal, lateral or rostrocaudal to the median raphe (dorsal raphe nucleus, pontine reticular formation, caudal linear nucleus or raphe pontis, respectively) failed to generate theta or in a few cases produced theta at very long latencies (> 24 min). Saline injections in the median raphe nucleus or control structures were without effect. The demonstration that agents injected into the median raphe nucleus that inhibit its activity (procaine and serotonin1A agonists) produce theta indicate that serotonin-containing median raphe neurons normally suppress theta or are involved in the control of hippocampal desynchronization. The present findings are consistent with previous work showing that median raphe nucleus stimulation desynchronizes the hippocampal electroencephalogram and that median raphe nucleus lesions produce constant theta, but are at odds with the proposal that serotonergic mechanisms may play a role in the generation of the theta rhythm.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1994

Basis for differential coupling between rhythmic discharges of sympathetic efferent nerves.

The relationships between activities of three sympathetic efferents [vertebral (VN); cardiac (CN); and renal nerves (RN)] of 45 chloralose-urethan anesthetized cats were investigated using multivariate spectral analysis. The multiple coherences measuring the extent to which one nerve signal may be predicted from the other two were very high (0.77-0.83) at the peak frequency of synchronized rhythmic activity, indicating that specific components comprised < 20% of the power in the nerve signals. The pattern of sympathetic activity was characterized by the partial coherences calculated for different nerve pairs after the components common for all three nerve signals were removed. In baroreceptor-intact cats, partialization on the CN signal drastically reduced the coherences between the VN and RN (0.25), whereas the coherences between the CN activity and either of the vasoconstrictors remained high after partialization on the other vasoconstrictor (0.52 and 0.43). In baroreceptor-denervated cats, partial coherence was high between vertebral and cardiac nerves (0.52) and low between renal and any other nerve discharge (0.19-0.20). In individual experiments, five different patterns of coupling were observed, and their separation was tested by cluster analysis.

Animals↗
PubMed1994

Characterization of neurons of the supramammillary nucleus and mammillary body that discharge rhythmically with the hippocampal theta rhythm in the rat.

We examined the activity of single cells of the supramammillary nucleus (SUM), the mammillary body (MB), and adjacent regions of the diencephalon with respect to the hippocampal electroencephalogram (EEG) in urethane-anesthetized rats. Twenty-nine of 170 cells were found to discharge synchronously with the theta rhythm of the hippocampus (theta-related neurons). All of the 29 theta-related cells were localized to the SUM or MB. A subset of theta-related cells of SUM and MB discharged in short-duration bursts comparable to the pyramidal complex spike cells of the hippocampus. In contrast to hippocampal complex spikes, however, which predominantly exhibit this mode of firing during non-theta states, the burst firing of SUM/MB cells was strongly correlated with the theta rhythm. The proportion of bursting neurons was higher in MB than in SUM. Using partial coherence analysis, we examined the relationship between SUM/MB theta-related cells and the two generators of theta of the dorsal hippocampus. The theta-related cells of MB showed a stronger correlation with "CA1" than with "dentate" theta, whereas no such asymmetry was found in the relationship between neuronal firing of SUM cells and the two generators of theta in the hippocampus. The foregoing suggests that the theta-related cells of MB are driven by descending projections from the hippocampal formation (CA1), whereas those of the SUM are not. The SUM and MB are intimately connected with the hippocampal formation--the SUM mainly via ascending projections to the dentate gyrus, and the MB via direct descending projections from the subiculum. Theta-related SUM/MB cells may be directly involved in the generation of theta and/or the transfer of theta rhythmicity to various parts of the limbic system and forebrain.

Action Potentials↗
PubMed1993

Differential sympathetic reactions during cerebral ischaemia in cats: the role of desynchronized nerve discharge.

1. Sympathetic nerve discharge (SND) of three postganglionic nerves with different functions and anatomical locations was simultaneously recorded at rest and during severe cerebral ischaemia (Cushing reaction). The three nerves, controlling the heart (inferior cardiac nerve), visceral (renal nerve) and skeletal muscle circulation (vertebral nerve), were selected with the assumption that their activity pattern will represent the differential central autonomic command to the major players of the circulatory response to cerebral ischaemia. 2. Changes in the power density spectra of the nerve signals, and in the pairwise coherence functions, elicited by the cerebral ischaemia, were evaluated separately for the rhythmic (R-SND, i.e. between 0 and 6 Hz) and high-frequency (HF-SND, i.e. between 12 and 100 Hz) components of the nerve signals. 3. The sympathetic nerve response to cerebral ischaemia developed in two phases. Phase 1 was a massive R-SND reaction and phase 2 was characterized by SND desynchronization and by the emergence of HF-SND. The power of HF-SND occupied a wide band between 12 and 80 Hz with maximum between 20 and 30 Hz. All three nerves were involved in the Cushing response but the magnitude and character of the reactions were specific for each nerve. In the cardiac nerve, the power of the rhythmic component of the discharge increased almost twice the control and remained dominant during the whole reaction, strongly modulating HF-SND during the second phase. In the vasomotor nerves, R-SND was suppressed during phase 2 and HF-SND occupied 65% of the total power of the signal. Near equal R- to HF-SND proportions, however, were reached on different activity levels in renal and vertebral nerves. Whereas total renal SND did not change, the power of the vertebral SND increased more than twice. In addition, desynchronization in the vertebral SND was preceded by a massive R-SND reaction during phase 1, which was missing in the renal nerve. 4. For all possible nerve pairs, R-SND was highly coherent before the reaction and remained so during intracranial pressure elevation, regardless of the direction and magnitude of the changes in absolute and/or relative power of this component in different nerves. On the other hand, HF-SND never correlated between any of the nerve pairs indicating that this component in each nerve originated from specific sources of regional sympathetic activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Coordination between cardiovascular and respiratory control systems during and after cerebral ischemia.

The dissociation of cardiovascular (arterial hypertension) and respiratory (depression) reactions to severe cerebral ischemia seems to be inconsistent with the usual cooperative behavior of the two systems and their role in managing disturbances in the central chemical environment. In the present study the Cushing reaction was elicited by transient increase of the intracranial pressure 4-11 times in each experiment. The pressor response and changes in the vertebral sympathetic nerve discharge (SND) were compared with the respiratory reaction and with changes in the phrenic nerve activity. The reaction in both nerves developed in two phases. In the phrenic nerve, an initial hyperactivity (increased discharge amplitude and frequency) coincided with augmentation of the rhythmic SND (phase 1) and complete nerve depression developed when the SND was desynchronized (phase 2). The transition in both systems correlated in their latencies and the severity of the ischemia needed for their stimulation. Repetition of the ischemic stimuli increased the occurrence of the respiratory-related rhythmicity in the SND and later changed its character from rhythmic amplitude modulation to respiratory-related high-frequency bursting SND coinciding with the inspiration. It is concluded that, despite the apparent dissociation between the cardiovascular and respiratory reactions, there is a parallel response between the neurophysiological correlates of the two systems to increasing severity of cerebral ischemia.

Animals↗
PubMed1992

Dorsal raphe neurons: synchronous discharge with the theta rhythm of the hippocampus in the freely behaving rat.

1. Single-unit activity of 30 dorsal raphe (DR) neurons was recorded along with the cortical and hippocampal electroencephalogram and neck muscle electromyogram in freely behaving rats during sleep-waking states. 2. On the basis of firing rates, DR cells were divided into slow-firing (S-cells), fast firing (F-cells), and very fast firing (FF-cells) units. The S-cells (8 units) fired at rates of < 10 Hz, the F-cells (11 units) at 10-40 Hz, and the FF-cells (11 units) at 55-70 Hz. 3. The activity of 17 of 30 DR units was correlated with the theta rhythm of the hippocampus. They included both slow and rapidly firing DR neurons. These cells typically fired irregularly (single spikes or short-duration bursts of activity) during non-theta states of quiet waking and slow-wave sleep. With the change of behavioral state to awake-moving or rapid eye movement sleep, the activity of these units switched to a regular bursting pattern synchronous with the hippocampal theta rhythm. Seven of these 17 units were classified as theta-rhythmic cells on the basis of the tight phase-locking of their discharge to the hippocampal theta rhythm. The remaining 10 units were classified as theta-modulated cells on the basis of a smaller but significant coherence between unit discharge and the theta rhythm.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Effect of preexisting brain ischemia on sympathetic nerve response to intracranial hypertension.

The performance of the sympathetic nervous system during sustained moderate cerebral ischemia (CI) was examined in the present study. For this purpose, a Cushing response was elicited repeatedly during incomplete global CI in anesthetized artificially ventilated cats after vagotomy and baroreceptor denervation. In control animals without CI, sympathetic activity in response to brief elevation of intracranial pressure (ICP) showed a well-repeatable two-phase reaction. During CI there was a progressive deterioration of background sympathetic nerve discharge (SND) over a period of 30 min. SND response to repeated elevation of ICP was initially similar to control response but later with progression of CI was seriously changed. 1) Instead of the usual hyperactivation, sympathetic nerve activity was depressed during intracranial hypertension. 2) The characteristic desynchronized activity either appeared later during the reperfusion period or remained absent. The progressive loss of SND response to raised ICP in developed CI was compared with the changes seen in experiments in which repeated ICP elevations were superimposed on asphyxia. These findings suggest that the sympathetic component of the Cushing reaction strongly depends on the actual state of brain stem autonomic circuits and may be seriously altered in pathological situations involving ischemic brain injury.

Animals↗
PubMed1990

[Markers of peripheral B lymphocytes and their function in IgA nephropathy].

Peripheral blood B-lymphocyte markers and functions were observed in 21 patients with IgA nephropathy (IgA NP), 18 patients with systemic lupus erythematosus (SLE) and 16 controls. IgA NP B-lymphocytes similarly to that of SLE B-lymphocytes expressed significantly higher positivity with Leu 1 (CD 5) monoclonal antibody than controls. CD 5 positive B-lymphocytes are thought to be a distinct subset of the B-cells (autoregulatory B-lymphocytes) inducible in IgA NP by lipopolysaccharide (LPS) stimulation in parallel to their expression of surface IgM heavy chain positivity. The activated state of IgA NP B-lymphocytes have been proved by their higher OKIa (HLA-DR) positivities but lower IOB1a (CD 21, C3b-receptor) and decreased IgG-Fc-receptor (ox- rosette) expression. IgA NP B-lymphocytes showed a higher IgA but also IgG and IgM polyclonal immunoglobulin production than control B-lymphocytes in co-cultures with T-lymphocytes. Not only regulatory T-lymphocyte subsets but also serum derived from IgA NP patients stimulated the immunoglobulin production of IgA NP B-lymphocytes.

Antibodies, Monoclonal↗