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T Ott

Publications and source records attributed to T Ott.

At least 91 records · Page 5Linked to original sources
PubMed1982

[Behavioral investigations following cholinergic deafferentiation of the hippocampus by septal lesions in rats (author's transl)].

Acquisition and retention of a visual discrimination task as well as changes in the exploratory activity and emotional state of the animals were investigated in rats with different lesions in the telencephalic septal area. The cholinergic deafferentiation of the hippocampal formation due to the lesion was determined by quantitative histochemical estimations of the loss in acetylcholine esterase activity in the various subfields of the hippocampus and the results were correlated to the behavioral experiments. Total bilateral septal lesion resulted mainly in an impairment of the acquisition processes of the discrimination task combined with an enhancement of the retention index. Slight tendencies for attenuated activity in the exploratory and emotional behavior were also present in this group. Assymmetric septal lesions leaving one lateral septal nucleus undamaged caused higher activities in the exploratory and emotional behavior. Some enhancement of the retention index was found, too. The degree of cholinergic innervation of the hippocampus was partially involved in the behavioral effects.

Acetylcholinesterase↗
PubMed1981

Stereochemical control of ribosomal peptidyltransferase reaction. Role of amino acid side-chain orientation of acceptor substrate.

The substrate specificity of the acceptor site of peptidyltransferase of Escherichia coli 70S ribosomes was investigated in the fMet-tRNA.A-U-G.70S ribosome and AcPhe-tRNA.poly(U).70S ribosome systems by using a series of 2'- and 3'-aminoacyldinucleoside phosphates as acceptors. These chemically synthesized compounds are analogues of the 3' termini of either 2'(3')-, 2'-, or 3'-aminoacyl transfer ribonucleic acids (AA-tRNAs) of the types C-A-aa, C-2'-dA-aa, C-3'-dA-aa, C-3'-dA-3'-NH-aa, and C-2'-dA-2'-NH-aa (aa = Phe, D-Phe, Lys, Leu, Ala, Glu, Pro, Gly, Asp, Met, and alpha-aminoisobutyryl). It was found that the 3'-aminoacyl derivatives of optically active amino acids are much better acceptors of N-formyl-L-methionine (fMet) or N-acetyl-L-phenylalanine (AcPhe) residues than the isomeric 2'-aminoacyl derivatives with affinity constant ratios (KM 2'/3') greater than 100. Likewise, C-A(D-Phe) is a weaker acceptor than the corresponding L derivative C-A-Phe. In contrast, all glycyl derivatives (C-2'-dA-Gly, C-3'-dA-Gly, C-3'-dA-3'-NH-Gly and C-2'-dA-2'-NH-Gly) are good acceptors of the fMet residue, with ratios (KM 2'/3') of approximately 2. On the basis of these results, a model for the stereochemical control of the peptidyl-transferase reaction is proposed. It assigns a major role to the orientation of the amino acid side chain in 2'- or 3'-AA-tRNA. A detailed model of the interaction of the acceptor terminus of 3'-AA-tRNA with the acceptor site of peptidyltransferase is also proposed. The model is strikingly similar to those for the active sites of proteolytic enzymes.

Acyltransferases↗
PubMed1981

Identical responses of the two hippocampal theta generators to physiological and pharmacological activation.

The possible existence of two separate RSA generators in the dorsal hippocampus raises questions as to the degree of coupling or independence of both. In order to answer these questions bipolar EEG recording were made in the CA1 and dentate gyrus of freely moving rats during conditions of RSA generation by different manipulations. The quantitative EEG parameters of simultaneous records were compared and cross correlation functions were calculated. Results indicate that even under different conditions of inducing RSA (physiological activation or injection of arecoline and nicotine) yielding RSA with different frequency characteristics, the quantitative EEG parameters were similar in both recordings. In addition, a high degree of concordance of both EEG was evidenced in the cross correlation function. These observations are discussed in terms of a high degree of coupling between both RS generators.

Animals↗
PubMed1980

Blockade of high frequency rhythmical slow activity by intrahippocampal injection of a glutamic acid antagonist.

Intrahippocampal injections of glutamic acid diethylester (GDEE) were performed in rats in order to study a possible implication of glutamate in the mediation of high frequency (8-12 Hz) rhythmical slow activity (RSA) elicited by 100 Hz electrical stimulation of the dorsomedial hypothalamus. This 8-12 Hz RSA was selectively and reversibly suppressed in hippocampal EEG 6 min and 15 min after 150 micrograms or 400 micrograms of GDEE, whereas no modifications were found in the low frequency RSA (6-8 Hz) evoked in hippocampus during exploratory behavior.

Animals↗
PubMed1980

The septo-hippocampal pathway: electrophysiological observations.

In 40 rats immobilized with gallamine evoked field potentials were elicited in the dorsal hippocampus by stimulation of the septal nuclei. Latency of the septohippocampal evoked potential (SHEP) elicited by stimulation of the medial septal nuclei, the variations of latencies and amplitudes with increasing stimulus intensities as well as the occurrence of frequency potentiation and post-tetanic potentiation allow the conclusion that the SHEP registered in the stratum granulare of dentate gyrus is mainly monosynaptically elicited. Nevertheless some data discussed in the paper point to the existence of a more complicated and not exclusively monosynaptic activation of granular cells caused by septal stimulation.

Action Potentials↗
PubMed1980

[Histochemical and biochemical study of the hippocampus and neocortex of the wistar rat. II. The activity of carboxylic acid esterases and transmitter enzymes after a learning experiment].

In the present paper the behaviour of the enzymes monoaminoxidase, GABA-transaminase, acetylcholinesterase, nonspecific cholinesterase, A-, B-, C-esterase and acid phosphatase was investigated by histochemical and biochemical methods for 1 min, 1, 4 and 24 h after a "brightness-discrimination" of male wistar rats in a Y-chamber. Learning induced significant changes of activity of the B-esterase in the hippocampus region 4 h (increase of 30%) and 24 h (decrease of 25%) and of the acetylcholinesterase in the cingular cortex 4 h after training (increase of 38%) are to be observed and regarded and discussed as hints for a changed protein synthesis (B-esterase) or altered synaptic activity (acetylcholinesterase). On the strength of these results and various findings in the literature it may be reputed as sure, that the protein synthesis of the cells of hippocampus in evident. Certain proteins show increased rates of synthesis by the influence of a learning experiment. These proteins are at least partially enzymes, serving as extension of the protein synthesis apparatus of the neurons and may be regarded as part mechanism of the intracellular regulation of the synaptic connectivity.

4-Aminobutyrate Transaminase↗
PubMed1980

The influence of cholinergic drugs on evoked field potentials in the gyrus dentatus of immobilized rats.

We reported previously the elicitation of presumably monosynaptic evoked field potentials in the dentate gyrus of immobilized rats by stimulation of the medial septal nuclei. The septo-hippocampal pathway mediating this evoked potential (SHEP) is widely assumed to be cholinergic in nature. In order to further verify this assumption we studied the effects of muscarinic drugs on the SHEPs. Scopolamine as muscarinic cholinolytic and arecoline as muscarinic cholinergic agent influenced the SHEP in the expected manner. We conclude that the SHEP is elicited by cholinergic muscarinic activation.

Animals↗
PubMed1978

The multiple forms of brain acetylcholinesterase. II. A suggestion of their functional importance.

The pattern of the multiple forms of the acetylocholinesterase (AChE, E.C. 3.1.1.7) of the rat brain is investigated using polyacrylamide gradient micro-gel electrophoresis with regard to a possible functional importance of this individual forms. The patterns of the AChE-forms of selected regions of the CNS are compared and certain differences could be shown. After increased cholinergic input (into the hippocampus by electrical stimulation of the nc. septi medialis) an aggregation of AChE subunits is detectable. Subletal intoxication with an irreversible inhibitor of AChE is followed by a faster recovery of the smaller forms. A suggestion of a possible functional role of the multiple forms of AChE is discussed.

Acetylcholinesterase↗
PubMed1978

Influence of post-training intrahippocampally applied oxotremorine on the consolidation of a brightness discrimination.

The posttraining intrahippocampal injection of oxotremorine revealed an improvement of the retention performance in a brightness discrimination task. The oxotremorine effect seemed to be dependent on distinct variables of training and was restricted to rats exhibiting a good acquisition performance. Scopolamine impaired the retention performance of animals with few training errors. The role of hippocampal cholinergic synapses for consolidation was discussed.

Animals↗
PubMed1978

Retention improvement by topical application of uridine monophosphate into different brain areas.

This study aimed to demonstrate the effect of uridine monophosphate (UMP) on the consolidation of a brightness-discrimination reaction after topical application of this RNA precursor into the hippocampus, the neocortex or the mesencephalic reticular formation (MRF). Thirty minutes before the rats started their training in a Y-chamber, UMP was injected into each animal through cannula implanted into the particular brain area. When injected into hippocampus or MRF UMP exerted no influence on acquisition, but after epidural UMP injection an impairment of acquisition was observed. After intrahippocampal or epidural UMP application the retention test carried out 48 hour after training showed a significant improvement in retention performance, whereas UMP injection into MRF showed no influence on retention. Consequently, the retention-improving effect of UMP is probably not induced by activation of ascending neuronal systems.

Administration, Topical↗
PubMed1977

Effects of orotic acid and pirazetam on cortical bioelectrical activity in rabbits.

In order to obtain further evidence of the pharmacological effects of retention-facilitating substances, the influence of sodium-orotate, methylglucamine orotate, and pirazetam on the bioelectrical activity of central nervous system structures were studied. Sodium orotate showed no influence on the cortical and hippocampal spontaneous EEGs of conscious nonimmobilized rabbits. The amplitude of the first surface-positive wave of the cortical evoked potential that was elicited by stimulation of tooth pulp was, however, significantly increased in long-lasting terms by both pirazetam and the two salts of orotic acid. Similarly, the three substances also influenced the changes in excitability induced by PTP of tooth pulp. The findings suggest that these chemicals facilitate in nonspecific manner responses to externally applied stimuli through central structures. The relationships between the altered stimulus response and the retention-facilitating action of these substances are discussed.

Animals↗