Biomedical subjects

B Eckersdorf

Publications and source records attributed to B Eckersdorf.

At least 19 recordsLinked to original sources

PubMed2001

Window effect of temperature on carbachol-induced theta-like activity recorded in hippocampal formation in vitro.

The effect of different temperatures of ACSF (18-42 degrees C) on carbachol (CCH)-induced field potentials were examined in the present study. Two hundred and thirty one experiments were performed on hippocampal formation slices maintained in a gas-liquid interface chamber. All slices were perfused with 50 microM CCH. A recording electrode was positioned in the region of CA3c pyramidal cells. The experiments gave two main findings. First, in a presence of continuous cholinergic stimulation the temperature of the bathing medium per se determined the rate of synchronization of the field potentials and pattern of EEG activity recorded. Second, within the temperature range from 33 degrees to 37 degrees C a window effect of temperature on CCH-induced theta-like activity (TLA) was noted: in this temperature range all slices tested responded only with one pattern of EEG activity-TLA. The results are discussed in light of temperature effects on hippocampal neuronal networks.

Action Potentials↗

PubMed2000

In vitro recorded theta-like activity in the limbic cortex: comparison with spontaneous theta and epileptiform discharges.

The generation of EEG theta rhythm in the mammalian limbic cortex is a prime example of rhythmic activity that involves central mechanisms of oscillations and synchrony. This EEG pattern has been extensively studied since 1938, when Jüng and Kornmüller (1938) demonstrated the first theta recordings in the hippocampal formation of rabbits. In 1986 in collaboration with Drs. B.H. Bland, S.H. Roth and B.M. MacIver we demonstrated for the first time that bath perfusion of hippocampal slices with the cholinergic agonist, carbachol, resulted in theta-like oscillations. Since this initial demonstration of in vitro theta-like activity, we have carried out a number of experiments in an attempt to answer the basic question: what are the similarities between cholinergic-induced in vitro theta-like activity and theta rhythm which naturally occurs in the in vivo preparation. Thus far, our studies have provided strong evidence that theta-like activity recorded in vitro shares many of the physiological and pharmacological properties of theta rhythm observed in vivo. The question whether in vitro theta-like oscillations reflect features of epileptiform activity is also addressed in this review.

Animals↗

PubMed1999

The effect of intraseptal procaine injection of hippocampal theta in freely moving cat.

Numerous studies have demonstrated that in the rodent, the septum is a critical site for the generation of hippocampla rhythmical field activity (theta, RSA). The aim of the present study was to clarify the role of the medial septal area in theta generation in the cat. Results indicate that (1) the microinfusion of the local anesthetic procaine into the medial septal region temporarily suppressed spontaneous as well as sensory and electrically induced hippocampal theta; (2) the suppression lasted 15 min and then amplitude and power of the hippocampal theta showed a progressive increase reaching preprocaine levels 60 min from the infusion onset. Theta frequency, in contrast, did not differ from control levels. The results provide evidence for the medial septal mediation of the hippocampal theta in the cat. This region is responsible for controlling theta amplitude but not its frequency. The present data supported the earlier results obtained in the rat and determined that the medial septal region plays a critical role in the generation of the hippocampal theta activity in cat.

Anesthetics, Local↗

PubMed1997

Theta-like activity in hippocampal formation slices: the effect of strong disinhibition of GABAA and GABAB receptors.

The involvement of GABAA and GABAB receptors in neural mechanisms responsible for the production of theta rhythms in hippocampal formation (HPC) slices is addressed in the present study. In a number of papers published in the last decade, we have demonstrated that theta-like activity can be successfully recorded in the limbic cortex maintained in vitro when the cholinergic agonists, acetylcholine, carbachol or muscarine, were added to the bath. Recently, we have also shown a strong GABAA modulation of the cholinergic-induced in vitro theta-like activity. This study presents a report of the first demonstration of in vitro theta-like field responses induced a consequence of simultaneously inhibiting hippocampal GABAA and GABAB receptors. HPC slices (350 microns) were maintained in a gas-liquid interface chamber (35 degrees C). Theta-like activity was induced in the presence of bath perfusion of bicuculline (GABAA antagonist) and 2-hydroxysaclophen (GABAB antagonist). This in vitro induced field response was antagonized both by muscimol (GABAA agonist) and baclophen (GABAB agonist). In addition, the experiments presented here revealed that bicuculline/2-hydroxysaclophen-induced in vitro theta-like activity also had a strong cholinergic M1 involvement: it was abolished by hemicholinium-3 (choline transport blocker) and pirenzepine (specific antagonist of M1 receptor), but not by gallamine (specific antagonist of M2 receptor). The results of the present study provided further evidence for a strong GABAergic/cholinergic interaction in the neural mechanism responsible for production of theta-like activity in the hippocampal formation slices.

Animals↗

PubMed1996

Kainic acid versus carbachol induced emotional-defensive response in the cat.

The emotional-defensive response (EDR) and accompanied neurotoxic and electroencephalographic (EEG) effects induced by injection of kainic acid (KA, 0.1; 0.2 microgram) into the midbrain periaqueductal grey region (PAG) and antero-medial hypothalamus (AMH) in the cat were examined and compared with EDR and accompanied neurotoxic and EEG effects induced by injection of cholinergic agent, carbachol (CCH), into the same sites. The injections of KA (0.2 microgram) into the PAG induced EDR which closely resembled the defense behavior typically observed after administration of CCH. However, in contrast to CCH-induced EDR, the defensive response induced by KA was found to be accompanied by EEG symptoms of epileptiform activity in the limbic cortex and a massive cell loss in the site of injection. It is proposed that KA-induced EDR and seizure activity may have resulted from the activation of different cell populations localized either in the vicinity of the injection (i.e., PAG region) and in the area remote from the injection loci, the limbic cortex. KA induced activation of PAG neuronal network would trigger the 'local response' (emotional-defensive response) and produce a remote effect-epileptiform activity.

Agonistic Behavior↗

PubMed1996

Cholinergic/GABAergic interaction in the production of EEG theta oscillations in rat hippocampal formation in vitro.

The generation of EEG theta rhythm (RSA) in the hippocampal formation is a prime example of rhythmic activity involving central mechanisms of oscillation and synchrony. Cholinergic nature of the in vitro and in vivo induced RSA has been undoubtedly established. Recently, we have demonstrated in vitro that the hippocampal formation theta rhythm resulted from interaction between the cholinergic and GABAergic systems. In the present study we have provided additional in vitro evidence that the hippocampal GABA-A receptors are actively involved in the mechanism of theta production. Specifically, we demonstrated that bicuculline-GABA-A antagonist significantly augmented carbachol induced theta response increasing amplitude and power of rhythmical slow waves. In separate experiments the carbachol+bicuculline induced RSA were studied in the presence of muscarinic M1 and M2 antagonists--pirenzepine and gallamine (respectively) and GABA-A agonist--muscimol. Both pirenzepine and muscimol antagonized induced theta oscillations and gallamine was found to be completely ineffective in blocking this EEG response. The results provided evidence for M1 cholinergic/GABA-Aergic interaction in mechanisms responsible for theta production.

Animals↗

PubMed1996

The spontaneous theta rhythm recorded from the hypothalamus posterior in the cat in vivo.

Rhythmical slow activity (theta) was mapped in the hypothalamic region in freely moving cats. We recorded well synchronized and high amplitude theta rhythm in the medial part of the hypothalamus posterior area. The EEG recordings made from lateral part of this hypothalamic region contained only irregular activity. These findings support earlier observations concerning the topography of hippocampal formation desynchrony and synchrony system. The observations of the present study also suggest that the hypothalamus posterior area is actively involved in the mechanisms responsible for generating theta oscillations in the cat.

Animals↗

PubMed1996

The rhythmic slow activity recorded from entorhinal cortex in freely moving cats.

The relationships between the entorhinal cortex (EC) and the hippocampal formation (Hipp) field potentials were examined in the present study. The detailed analyses of the signal let us group the patterns of theta appearance into three categories: (1) Theta rhythm dominating in both recordings from the EC and from the Hipp (2) Theta rhythm dominating in the Hipp with irregular activity in the EC (3) Theta rhythm dominating in the EC with irregular activity in the Hipp. These findings provide the evidence for the intrinsic generator of theta rhythm to be localized in entorhinal cortex in cats.

Animals↗

PubMed1995

Regional specificity of the emotional-aversive response induced by carbachol in the cat brain: a quantitative mapping study.

In this paper, the emotional-aversive response induced by intracerebral injection of carbachol has been studied in cats by recording their vocalization as an index of emotional behavior. The carbachol-induced responses were quantitatively mapped in the basal forebrain and diencephalic regions using the cumulative time of the animal's vocalization as a measure of response. The areas inducing the emotional- aversive response extended along two axes: 1. longitudinally along the neuraxis, from the reticular formation through the hypothalamus to the rostro-basal forebrain; and 2. vertically along the fornix, from the mediobasal hypothalamus to the septal area. The highest magnitude of the response (vocalization time) was obtained from a strip of tissue extending from the septum and preoptic area to the dorsal perifornical area, the dorsomedial hypothalamic nucleus, the paraventricular nucleus and the periventricular stratum. The pattern of distribution of reactive and nonreactive sites showed anatomic specificity, with the highest sensitivity found within the close periventricular tissue of the third ventricle. It is suggested that carbachol mapping selectively delineates the muscarinic cholinoceptive portion of the aversive, emotional brain system.

Animals↗

PubMed1994

Muscarinic (M1) mediation of carbachol-induced theta in the cat entorhinal cortex in vitro.

Entorhinal cortex slice preparations obtained from the cat exhibited theta rhythm during perfusion with 50 microM carbachol. The effect of carbachol was antagonized by the muscarinic blocker atropine sulphate, but not by hexamethonium and mecamylamine, which are antagonists of the nicotinic receptor. Further analysis of the pharmacological profile of these carbachol-induced theta oscillations showed that M1 receptor subtype to be involved in mediation of this EEG activity: the theta rhythm was antagonized by the M1 receptor blocker pirenzepine, but was unaffected by gallamine, an antagonist of the M2 receptor subtype.

Animals↗

PubMed1993

Muscarinic (M1) mediation of hippocampal spontaneous theta rhythm in freely moving cats.

The effects of intrahippocampally applied different doses of muscarinic (atropine sulphate, pirenzepine, gallamine) and nicotinic (hexamethonium, mecamylamine) antagonists on the spontaneous theta rhythm in the cat hippocampal formation were investigated. The injections of atropine and pirenzepine abolished spontaneous theta but administration of gallamine did not affect the EEG pattern. The intrahippocampally administered nicotinic blockers, hexamethonium and mecamylamine, were completely ineffective in antagonizing theta waves. The data suggest that the spontaneous theta rhythm in the cat is mediated by the M1 receptor subtype.

Animals↗

PubMed1993

Emotional-aversive nature of the behavioral response induced by carbachol in cats.

Intrahypothalamic-preoptic application of carbachol induces a characteristic, emotional-aversive response in cats similar to their natural defensive behavior. This study was undertaken to provide quantitative evidence that the magnitude of the carbachol-induced, emotional-aversive response follows the same rules as natural responses to threat. An aversive emotional response can be described in terms of a spatiotemporal relationship between the animal and the relevant threat stimulus (potential danger). The physical distance to the threat stimulus and its movements should be predictive of the magnitude of the emotional response. The goal of the study was to test the relationship for the carbachol-induced response. The presentation of a threat stimulus (a human hand) to cats injected with carbachol caused a significant increase in vocalization. The magnitude of the response was inversely proportional to the physical distance between the cat and the threat stimulus. The hand in motion caused significantly longer vocalization than the immobile hand and cats not familiar with the experimental situation vocalized significantly more than those that had been exposed to the hand before. The spatiotemporal relationship between the animal and the threat stimulus strongly suggests that the carbachol-induced response is emotional and aversive in nature and does not differ from the relevant natural responses.

Animals↗

PubMed1992

Carbachol-induced rhythmic slow activity (theta) in cat hippocampal formation slices.

Application of the cholinergic agonist, carbachol, produced theta-like rhythmical waveforms, recorded in the stratum moleculare of the dentate gyrus in the cat hippocampal formation slices. This effect of carbachol was antagonized by atropine but not D-tubocurarine. These results provide first direct evidence that the hippocampal formation neuronal network in the cat is capable of producing synchronized slow wave activity when isolated from pulsed rhythmic inputs of the medial septum.

Animals↗

PubMed1992

Carbachol-induced theta-like activity in entorhinal cortex slices.

The present study was conducted for two purposes: the first was to evaluate whether activation of cholinergic receptors of the entorhinal cortex in vitro (complete deafferentation) with carbachol (100 microM) was capable of producing theta (theta)-like slow activity. The second purpose was to determine whether carbachol-induced slow waveforms were mediated by muscarinic or nicotinic receptors. We demonstrated that carbachol was capable of producing theta-like slow activity. This activity was not altered by nicotinic antagonists, (+)-tubocurarine and hexametonium. Atropine and scopolamine, in contrast, completely blocked in vitro induced slow waves, indicating entorhinal muscarinic receptors to be actively involved in the mechanism generating cholinergic theta rhythm.

Animals↗

PubMed1992

Cholinergically-induced theta-like oscillations in the hippocampal formation of freely moving cats.

The present investigation was undertaken to assess the role of the cholinergics in the production of theta (theta) rhythm in the cat hippocampal formation. Intrahippocampal injections of carbachol, muscarine or eserine produced a well synchronized high frequency cholinergic theta activity (HFC) in a range of 5-12 Hz. Subsequent intrahippocampal injection of muscarinic antagonist, atropine sulphate, completely blocked this cholinergic-induced EEG pattern. The nicotinic antagonist, hexamethonium, was without any effect on the cholinergic-induced rhythmical waves. We suggest that HFC may result from the activation of the oscillatory mechanism intrinsic to the cat hippocampal formation.

Animals↗

PubMed1992

Hippocampal rhythmic slow activity (RSA) in the cat after intraseptal injections of muscarinic cholinolytics.

Influence of intraseptal injections of cholinolytics on hippocampal rhythmic slow activity (RSA) was investigated in cats. Results of the first experiment have shown that neither atropine (At) nor scopolamine (Sc) injected into the medial septum in doses of 20 micrograms prevented the induction of RSA by a cholinergic (carbachol-CCh) stimulation of the anterior hypothalamus as well as by electrical stimulation of posterior hypothalamus or periaqueductal grey substance (PAG), and were only partially effective in prevention of the spontaneous RSA. RSA did not appear spontaneously and could not be induced by electrical brain stimulation after intraperitoneal injections of At (2.0 mg/kg) or Sc (0.2 mg/kg). Results of the second experiment have shown that intraseptal injections of At (5.0 or 10.0 micrograms) are also ineffective in prevention of RSA induction by CCh (2.5 micrograms) injected into the same septal locus. The data suggest that the medial septum cannot be regarded as the common muscarinic link within the RSA generating system of the cat.

Animals↗

PubMed1990

Evidence for involvement of endogenous acetylcholine in emotional-aversive response in the cat.

1. The purpose of the present study was to provide evidence for involvement of endogenous acetylcholine in naturally as well as pharmacologically induced emotional behaviour in the cat. 2. Emotional-aversive responses of 10 cats were naturally evoked by presentation of a dog or the responses were pharmacologically induced by intracerebral injections of cholinomimetics. 3. Naturally evoked emotional behaviour was abolished by i.p. pretreatment with atropine sulfate (1 mg/kg), but not by atropine methyl nitrate, or it was significantly decreased by bilateral intracerebral injection of atropine sulfate (5 micrograms/microliter). 4. On the other hand, intracerebral injections of physostigmine (100 micrograms/microliter), an acetylcholinesterase inhibitor which elevates the level of endogenous acetylcholine, induced the fully developed emotional-aversive response comparable with natural behaviour and with responses induced by carbachol (10 micrograms/microliter). 5. The results demonstrate that the endogenous acetylcholine in the basal forebrain and diencephalic areas play a role in naturally occurring emotional aversive behaviour in cats.

Acetylcholine↗

PubMed1989

Kainic acid lesions of the cat's midbrain periaqueductal grey region and emotional-defensive response evoked by carbachol injection to the same loci.

Injections of carbachol (CCh) through a chronic cannula into the midbrain periaqueductal grey region (PAG) of the cat induced an emotional-defensive response (EDR) which was evaluated by duration and number of growls in a 30-min experimental session. That response was examined before and after injection of kainic acid (KA) to the same loci of midbrain. Injections of this excitotoxin into the PAG decreased EDR level. The degree of changes depended on the agent dose. A low KA dose (3 microgram/2 microliters) produced only prolongation of EDR latency, whereas a high dose of KA (6 micrograms/2 microliters) brought a statistically significant reduction of response level (reaching approximately 80%). The results have demonstrated the sensitivity of these cells of the PAG that are responsible for EDR.

Aggression↗