Anisomycin blocks the late phase of long-term potentiation in the dentate gyrus of freely moving rats.

Freely moving rats, chronically implanted with stimulation electrodes in the medial entorhinal cortex and recording electrodes in the dentate gyrus, received two 400 micrograms intraventricular injections of anisomycin during a tetanization procedure that induced a long-lasting potentiation (72 hours) of the monosynaptic field potential. Inhibition of protein synthesis during the tetanization procedure did not immediately influence the induction of long-term potentiation (LTP). However, 3-4 hours after the beginning of tetanization the potentiation effect decayed progressively and was abolished totally during the remaining 7 day observation period.

Failure of translational repression in the phage f2 op3 mutant is not due to an altered coat protein-RNA interaction.

A secondary phenotype of the op3 mutant of RNA bacteriophage f2 is the absence of translational repression of the phage replicase gene by the phage coat protein. We have synthesized RNA fragments corresponding to the site of translational repression for both the wild type and the op3 mutant. Using a quantitative assay, we show that the affinity of the closely related R17 coat protein for the mutant and wild type RNA fragments is the same.

Aminergic blockade modulates long-term potentiation in the dentate gyrus of freely moving rats.

Long-term potentiation (LTP) was induced in the dentate gyrus of freely moving rats by tetanic stimulation of the medial entorhinal cortex under conditions of catecholamine depletion by 200 mg/kg alpha-Methyl-para-tyrosine (AMPT) or blockade of alleged dopamine receptors by 0.5 mg/kg haloperidol. Both substances did not change significantly the normal excitability of the glutamatergic perforant pathway, but affected the establishment of LTP.

Enzymatic synthesis of a 21-nucleotide coat protein binding fragment of R17 ribonucleic acid.

An oligoribonucleotide with a sequence identical with the bacteriophage R17 replicase initiator region has been synthesized. The sequence also encompasses the binding domain of R17 coat protein, which is known to act as a translational repressor at this site. The 21-nucleotide fragment was synthesized entirely by enzymatic methods, T4 RNA ligase being used to join shorter oligomers.

Reversal of T4 RNA ligase.

Unexpected products detected in oligoribonucleotide synthesis reactions catalyzed by T4 RNA ligase are shown to be a result of a partial reversal of the enzyme reaction. A transfer assay for the reversal of the third step in the RNA ligase reaction mechanism and an exchange assay for the reversal of both the second and third steps are described. Reversal is confirmed by the formation of the expected covalent intermediates, adenylylated donor and adenylyl ligase, from a reaction containing 5'-AMP, unadenylylated ligase, and the tetranucleotide (Ap)3Cp.

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.

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.

Hemodialysis without heparin infusion using Cordis Dow 3500 hollow fiber.

1) Hemodialysis for 3-4 hrs with C-3500 without heparin infusion is possible. 2) Hemodialysis without heparin with C-3500 may be preferred for patients with active or potential bleeding. 3) Excessive clotting may occur when blood flow is less than 250 ml/min, blood transfusion is used during dialysis or dialysis is longer than 3.

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.

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.

[Effect of psychopharmaceutic agents on cortical potentials and long-lasting post-tetanic changes in excitability released through stimulation of the dental pulp].

Short-time tetanic stimulation of the tooth pulp with square pulses affords, depending on the stimulation parameters selected, a long-lasting facilitation in the response of subsequently applied test stimuli in the sensomotor cortex of rabbits. The benzodiazepin derivatives, chlorodiazepoxide, nitrazepam (10 mg/kg i.p.

[Long-lasting changes of irritability in the somatosensory cortex of rabbits following tetanic stimulation of the tooth pulp].

Tetanic stimulation of the tooth pulp produced long lasting increases in potentials released by stimulation of the tooth pulp with single stimuli in the sensomotor cortex of rabbits. Stimulation with 200 impulses/sec for 5 sec produced changes of irritability that are demonstrable for 10-50 min depending on the intensity of stimulation. The lower rate limit for producing such changes is 25 impulses/sec.