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Biomedical subjects

P Monmaur

Publications and source records attributed to P Monmaur.

36 records · Page 2Linked to original sources
PubMed1984

Decrease in both choline acetyltransferase activity and EEG patterns in the hippocampal formation of the rat following septal macroelectrode implantation.

A decrease in both choline acetyltransferase (CAT) activity and theta (theta) rhythm were observed in the hippocampal formation of rats implanted with a macroelectrode in the dorsomedial part of the septum. The decrease in CAT activity and in theta occurred simultaneously and in parallel, and there was no instance where the two parameters were uncoupled. These observations suggest that a common neurophysiological mechanism is involved in both CAT activity control and theta rhythm production in the hippocampal formation. From a methodological point of view, these observations should be borne in mind in septohippocampal investigations using septal electrode implantation procedures.

Animals↗
PubMed1983

Topographic organization of septal cells innervating the dorsal hippocampal formation of the rat: special reference to both the CA1 and dentate theta generators.

We determined the topographic organization of septal cells innervating monosynaptically the two generators of theta rhythm of the rostral hippocampal formation of the rat. Under ether anesthesia, horseradish peroxidase (HRP) was injected into the dorsal CA 1 region close to the corpus callosum, the ventral part of CA 1 region close to the hippocampal fissure, and the dentate hilus. The HRP micropipet tip was positioned in these hippocampal-dentate sites by recording the hippocampal EEG through the micropipet itself before HRP injection. The major findings were: (i) Injection of HRP in the superficial part of the dorsal CA 1 region (i.e., the septal pole) resulted in labeling of neurons situated mainly in the diagonal band of Broca, ipsilateral to the injection site. (ii) Injection of HRP in the deep part of the dorsal CA 1 region resulted in the labeling of a few cells scattered in the septal region ipsilateral to the injection site. (iii) After injection of HRP in the dentate hilus, labeled cells were selectively detected in the rostral half of the medial septal nucleus mainly ipsilateral to the injection site. A high degree of organization was revealed in the connections between the septal region and the rostral hippocampal formation of the rat, two cerebral regions critically involved in theta production. The results are relevant to the two-generator hypothesis of theta.

Animals↗
PubMed1982

Radioautographic analysis of [14C]2-deoxyglucose uptake in hippocampal formation of the rat during enforced locomotor activity-induced theta.

The [14C]2-deoxyglucose ( [14C]2-DG) uptake in the hippocampal formation of the rat was studied following enforced locomotor activity-induced theta (M theta). M theta was found to be essentially associated with an increase in 2-DG uptake in the stratum oriens of the hippocampal CA1-CA2 areas. These data contrast with our previous findings that physostigmine-induced theta (I theta) is specifically associated with a decrease in 2-DG uptake in the stratum lacunosum moleculare of hippocampal CA1-CA2 areas. When both of our sets of radioautographic data are considered together, M theta and I theta appear to have a distinct neurophysiological basis.

Animals↗
PubMed1982

The neocortex of rats behaving in a driven rotating wheel shows a band characterized by preferential uptake of deoxyglucose.

In comparison with control rats placed in a glass chamber, the neocortex of experimental rats performing in a motor-driven activity wheel shows a limited region of high metabolic activity, as revealed by the deoxyglucose radioautographic method. This region consists of a bilateral band located in the somesthetic area SI. An overlap of this labeling with the sensory and/or motor cortical representation of the head, and especially a correlation with head posture and movements, is discussed.

Animals↗
PubMed1982

Hippocampal theta rhythms from CA1 and dentate generators during paradoxical sleep of the rat: differential alterations after septal lesion.

Hippocampal theta (theta) rhythm was recorded from CA1 and dentate generators respectively, before and after septal lesion in the freely moving rat. It was observed that theta recorded from CA1 generator and theta recorded from dentate generator can be differentially affected by the lesion. In agreement with our previous data, these findings strongly support the hypothesis that CA1 and dentate generators producing the hippocampal theta are functionally independent. The existence of two independent septo-hippocampal neural systems which might mediate theta CA1 and theta dentate separately is discussed.

Animals↗
PubMed1981

Phasic hippocampal activity during paradoxical sleep in the rat: selective suppression after diazepam administration.

The effects of diazepam on tonic (T theta) and phasic (P theta) components of the paradoxical-sleep hippocampal theta rhythm were studied in the rat. Results show that diazepam, a benzodiazepine analogue known to interfere with the putative neurotransmitter gamma-aminobutyric acid (GABA) in the mammalian central nervous system, selectively abolishes P theta. They confirm previous data according to which sedative/anaesthetic drugs cause an apparent dissociation of T theta and P theta of the paradoxical-sleep hippocampal theta rhythm. Moreover, they suggest a possible involvement of GABA in the neurochemical mechanisms underlying P theta in the rat.

Animals↗
PubMed1980

[Hippocampus theta rhythms of wakefulness and paradoxical sleep in the rat : a comparative study].

In the urethane anaesthetized Rat, hippocampal theta rhythm has been recorded during wakefulness and during paradoxical sleep under the same behavioral and postural conditions. A comparative study of these two rhythms shows the following data: 1) The wakefulness and paradoxical sleep theta rhythms significantly differ from each other in frequency and amplitude. 2) The wakefulness theta rhythm recorded in CA1 region and the paradoxical sleep theta rhythm recorded in dentate gyrus can be selectively eliminated by a septal lesion. In agreement with our previous data the present results are in favor of the existence of two kinds of theta activity having different anatomophysiological bases: one associated with wakefulness and the other with paradoxical sleep. In addition, these results suggest that the two intrahippocampal generators of theta rhythm are functionally independent.

Animals↗
PubMed1978

[Experimental dissociation between hippocampal theta activity in wakefulness and hippocampal theta activity in paradoxal sleep in the rat].

The effects of electrolytic lesion of the septum on the theta activity of the dorsal hippocampus were studied in the chronically implanted Rat during wakefulness and paradoxical sleep. The experimental results show that depending on its localization, septal lesion can either: (1) eliminate the wakefulness theta rhythm without suppressing that of paradoxical sleep; (2) eliminate the paradoxical sleep theta rhythm without suppressing that of wakefulness. These results suggest that there are two kinds of theta activity having different anatomophysiological bases and a different functional significance: one associated with wakefulness and the other with paradoxical sleep.

Animals↗
PubMed1978

[Effects of bilateral dorsolateral pontine tegmentum lesions on hippocampus theta rhythm during paradoxical sleep in the rat].

Electrolytic lesions of the dorsolateral pontine tegmentum aimed at the locus coeruleus (LC) were performed bilaterally in 13 chronically implanted Rats. Following lesions, transient alterations of characteristic components of theta rhythm appeared. No shortening of duration of paradoxical sleep (PS) was observed. These results do not support the hypothesis that neurons of LC are directly involved in the production of theta rhythm during PS; moreover they seem not to be necessary to the normal appearance of this state of sleep.

Animals↗
PubMed1977

[Ontogenetic analysis of the theta rhythm during paradoxical sleep in rats].

In the rat, an ontogenetic study of theta rhythm during paradoxical sleep shows a clear evolution between the 14th and the 30th postnatal day. During this period, its mean frequency increases from 5 to 7 cycles per second, and its spectrum shows significant changes. These parameters (mean frequency and spectral components) of the theta rhythm could be a useful index of brain maturation in the rat.

Animals↗
PubMed1976

[Statistical relationship between "slow-wave sleep" and "paradoxical sleep" in rats].

In the Rat, statistical analysis of slow sleep (SS) and paradoxical sleep (PS) episodes disclosed two significant (p less than 0,01) positive correlations: (1) Over a four-hour period, the mean duration of PS episodes was correlated to the mean of the just preceding "light" SS episodes; (2) On the contrary, from cycle to cycle of sleep-wakefulness, the duration of each PS episode was correlated to that of the "light" SS episode of the next cycle.

Animals↗
PubMedDate not supplied

Short-term memory, exploration and locomotor activity in aged rats.

Behavioral profiles of young (3-6 months) and aged (24-27 months) rats were compared in three respects: (1) short-term memory, (2) exploration and (3) locomotor activity. Compared to young rats, aged rats were impaired in the 8-arm radial maze acquisition, but not in the delayed reinforced alternation acquisition. They had lower scores of spontaneous alternation, of exploration of a novel object and of a novel environment. Their exploratory activity was lower in a simple environment but similar in a complex environment. Their spontaneous locomotor activity was lower during the dark part of the cycle (8 p.m.-8 a.m.) but not different during the light part of the cycle (8 a.m.-8 p.m.). These results suggest that with respect to short-term memory and exploration, differences between aged and young rats may be influenced by a "complexity" factor and may be secondary to differences in motivation and reactions to novelty.

Aging↗