PubMed Health⌕ Search

Biomedical subjects

S Gralewicz

Publications and source records attributed to S Gralewicz.

53 records · Page 3Linked to original sources
PubMed1983

Effects of ethanol on after--discharges evoked by electrical stimulation of hippocampus in rabbits.

The influence of ethyl alcohol on the after-discharges provoked by electrical stimulation of dorsal hippocampus in rabbits was studied. The after-discharges were registered from frontal cortex reticular mesencephalic substance and contralateral hippocampus. The hippocampus was stimulated seven times every 30 min. in two sessions performed in a 7 days' interval. In the second session ethanol in doses 0.8 g/kg i.v. and 0.4 g/kg p. o. and i. v. was administered. Ethanol administered intravenously in a small dose increase, whereas in a larger dose prevented the increase of after-discharge duration during the session. The influence of ethanol on after-discharges correlated with its initial blood concentration.

Animals↗
PubMed1982

Effects of atropine sulphate on hippocampal rhythmic slow activity during a conditioned locomotor response in the cat.

In cats atropine sulphate injected intraperitoneally in doses of 1.0 and 2.0 mg/kg abolished the hippocampal rhythmic slow activity (RSA) accompanying the performance of instrumental active avoidance response in a shuttle box. The action of atropine consisted in a gradual elimination of RSA, the RSA of slower frequency occurring during latency (the period of attentive immobility between the CS onset and the beginning of the conditioned locomotor response) and during the poststimulus period disappeared first, and that of a higher frequency, accompanying the initiation of the conditioned locomotor response and barrier crossing disappeared last. The speed of this process was dose dependent. The data show that the whole spectrum of RSA in the cat is atropine sensitive, but the level of this sensitivity depends on the RSA frequency.

Animals↗
PubMed1981

Hippocampal electrophysiological correlates of an avoidance behaviour in the cat.

In 8 cats the hippocampal EEG was investigated during the avoidance behaviour in a shuttle box. It has been found that at the criterion phase of training the performance of the conditioned response (crossing a barrier) was accompanied by rhythmic, slow activity (RSA) in majority of trials. In cats with electrodes located in the dorsal part of the hippocampus a small irregular activity (SIA) might also appear during the AAR performance, especially in trials characterized by very short latencies and a fast locomotor response. Attentive postures during intertrial intervals, during latency and during conflict trials (in which the spatial location of the directional CS had been changed) were also accompanied by RSA. In the last case the RSA frequency reached the same values as during the AAR performance, though the locomotor response was absent. It has been found, however, that when RSA was present at the moment of the CS onset the latencies were shorter and the performance faster. The data support the view according to which RSA reflects a certain level of motor readiness but is not linked directly to the behavioural output.

Animals↗
PubMed1978

Proactive and retroactive effects of hippocampal stimulation on active avoidance learning, hippocampal EEG and brain acetylcholinesterase activity in cats.

The subject of this investigation were the effects of electrical stimulation of the hippocampus on the acquisition of active avoidance response (AAR) in a shuttle-box. The stimulation (200 microamperes, 50/s, negative rectangular pulses of 1.0 ms duration) was applied once for 10 s before or after each training session. It was found that the application of hippocampal stimulation before each session facilitated the acquisition of AAR; discontinuation of the stimulation after training did not cause a decrease of AAR performance. Application of the stimulation after each session inhibited learning in four out of six cats. However, the level of AAR performance increased rapidly in these cats after inversion of the trials-stimulation sequence. It was also found that the intensity of the somatic and vegetative symptoms evoked by stimulation (stupor, salivation, twitching of facial muscles, pupil dilatation, crying) increased gradually in successive experimental sessions, suggesting the development of the 'kindling effect in cats stimulated before each session. In cats stimulated after each session the intensity of these symptoms was greatly diminished as compared to sessions where the stimulation was not preceded by the avoidance training, or they did appear at all. However, normal sensitivity to stimulation returned after several applications of hippocampal stimulation before each experimental session. Electroencephalographic studies showed that hippocampal stimulation with the use of the same parameters as those used during training evoked hippocampal afterdischarges lasting 5-60 s. No changes of aceltycholinesterase activity in different brain regions were found in consequence of such stimulation.

Acetylcholinesterase↗
PubMed1978

Facilitatory and inhibitory effects of strong electrical hippocampal stimulation on performance of two-way avoidance response in cats.

The influence of a strong, seizure inducing electrical stimulation of the hippocampus on the performance of the active avoidance responses in a shuttle-box was studied. The stimulation (a 10 s train of rectangular, negative pulses, 50/s 200 microamperes) was applied at different stages of training 2 min before experimental sessions. The stimulation evoked a facilitatory or inhibitory effect on the avoidance performance. The kind of effect depended on the level of stabilization of the avoidance response. At an early stage of training facilitatory effect dominated, an inhibitory effect prevailed after stabilization of the avoidance response. Intraperitoneal administration of atropine sulphate decreased the inhibitory effect of stimulation. The results confirm the supposition that hippocampal stimulation influences the performance of conditioned active avoidance responses in a similar way as electroconvulsive shock does.

Animals↗
PubMed1976

Electrical stimulation of the hippocampus and acquisition of the conditioned avoidance response in shuttle-box in cats.

The effects of electrical stimulation and electrolytic lesions of the posterior part of the hippocampus on acquisition of the active avoidance response (AAR) in shuttle-box were studied in 35 cats. Both weak or strong hippocampal stimulation applied simultaneously with conditioned stimulus (CS) facilitated the acquisition of AAR. After discontinuation of stimulation the level of AAR performance in response to CS alone decreased in cats trained with the use of strong stimulation. However, if the stimulation was applied before each experimental session the level of AAR performance did not differ from that observed during the final phase of training. These changes of AAR were not observed in cats trained with the use of weak stimulation. The application of hippocampal stimulation alone did not evoke AAR in shuttle-box after training independently of stimulation parameters. There were no differences in the speed of AAR acquisition between unoperated cats, implanted controls and cats with lesions in the posterior part of the hippocampus.

Animals↗
PubMedDate not supplied

Interaction of chlorphenvinphos with cholinergic receptors in the rabbit hypothalamus.

The purpose of this study was to find out whether chlorphenvinphos (CVP), an organophosphorous pesticide, interacts with the muscarinic cholinergic receptors in CNS. To attain this goal, the effects of intrahypothalamic injections of oxotremorine (Ox), a muscarinic agonist, and physostigmine (Phys), a carbamate anticholinesterase, were compared with those produced by intrahypothalamic injections of CVP in the rabbit. It was found that the infusion of Ox (20 micrograms) as well as Phys (200 micrograms) into the anterior hypothalamus leads to an increase in the 4-7 Hz theta rhythm in the hippocampus and to the appearance of behavioral symptoms suggestive of a threat response. In the case of Ox, the effects could be prevented by injections of 20 micrograms scopolamine, a muscarinic antagonist. Pretreatment of the hypothalamus with 100 micrograms hemicholinium (HC-3) did not prevent the effects of Phys injected 2 h later. (HC-3 prevents the resynthesis of acetylcholine by blocking choline reuptake. This leads to a gradual depletion of ACh stores and to an inhibition of the cholinergic transmission). It suggests that Phys activates directly postsynaptic muscarinic receptors. Intrahypothalamic injections of CVP in doses of up to 1360 micrograms produced no overt changes in behavior nor in the hippocampal EEG of the rabbit and did not prevent the effect of subsequent injections of Ox. This suggests that CVP is neither an agonist nor antagonist of the muscarinic receptors in the rabbit hypothalamus.

Acetylcholinesterase↗
PubMedDate not supplied

Behavioral changes following 4-week inhalation exposure to pseudocumene (1,2,4-trimethylbenzene) in the rat.

Pseudocumene (1,2,4-trimethylbenzene, TMB) is a component of several solvent mixtures. During recent studies on rats we investigated the effect of a 4-week (6 h/day, 5 days/week) inhalation exposure to TMB at concentrations of 0, 25, 100, or 250 ppm on radial maze performance, open field activity, passive avoidance, active two-way avoidance, and shock-induced changes in the pain sensitivity reflecting the magnitude of the shock-induced fear response (hot plate test). The tests were performed between days 14 and 54 after the last exposure. The radial maze performance was not disturbed in any dose group. During testing in the open field grooming was significantly increased in rats exposed to 100 ppm TMB. In rats exposed to 100 and 250 ppm TNB, a foot shock applied after stepping off an elevated platform (a safe area) resulted in a significantly smaller increase in the step-down latency (i.e., passive avoidance, on days 3 and 7 after the foot shock) than in sham-exposed animals. Learning of a two-way active avoidance was slightly retarded in rats exposed to 250 ppm of TMB. Results of the hot plate test revealed no differences between groups in the paw sensitivity to heat (54.5 degrees C) before a 2-min intermittent food shock, but in rats exposed to 100 and 250 ppm of TMB the foot shock-induced fear response persisted apparently longer. These results suggest that inhalation exposure to TMB may lead to long-lasting disturbances in CNS functions.

Animals↗
PubMedDate not supplied

Amphetamine anorexia in cats: the effect of encouraging to ingestive behavior.

The effect of encouraging to ingestive behavior was examined in cats pretreated with amphetamine (AMPH) in a dose sufficient for evoking anorexia (2 mg/kg). AMPH evoked complete refusing of spontaneous food ingestion in all animals. However, the cats could eat in even frantic manner when they were encouraged to ingestive behavior by moving the bowl with food around the place where the animal was sitting in the experimental cage. This result reveals that so called "anorexic syndrome" does not consist simply in a loss of appetite. It may be temporarily suppressed by some additional external stimuli which enable to channel the animal's behavior to the ingestive one.

Amphetamines↗
PubMedDate not supplied

Changes in the amplitude of hippocampal evoked potentials during avoidance behaviour in the cat.

In seven cats changes in the hippocampal EEG and in the hippocampal evoked potentials (EP-s) produced in Ca-1 field by stimulation of the contralateral hippocampus, ipsilateral hippocampus and entorhinal cortex were investigated during a conditioned, active avoidance response (AAR). The highest amplitudes of the EP-s were observed before the CS (conditioning stimulus) onset, when the animal was relaxed and an irregular activity of variable amplitude and frequency, dominated in the hippocampal EEG record. The lowest amplitudes were recorded during performance of the conditioned locomotor response, associated with a rhythmic, slow activity (RSA) or, occasionally, with a small irregular activity (SIA) in the hippocampal EEG. The course of changes in EP amplitude during trials might be expressed in the form of an U-shaped curve. The data suggest that changes in the hippocampal EP-s and in the hippocampal EEG are due to changes in the intensity of the same unspecific process.

Animals↗
PubMedDate not supplied

Effects of electrical stimulation of the hippocampus on the behavior of cats and their defensive conditioned responses in a shuttle-box.

In seven cats the effect of posterior hippocampal stimulation on the number of passings over a transverse bar in a shuttle-box was determined before and after induction of a conditioned avoidance reaction in the same experimental situation. The effect of hippocampal stimulation on the reaction was also studied applying it during the conditioning stimulus. It was observed in these experiments that a behavior imitating the conditioned reaction acquired during training, appeared in most cases during stimulation. It was also found that only strong stimulation of the posterior hippocampus applied together with the conditioning stimulus inhibited the reaction.

Animals↗