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M Rowan

Publications and source records attributed to M Rowan.

12 recordsLinked to original sources
PubMed1991

Inhibition of an N-methyl-D-aspartate induced short-term potentiation in the rat hippocampal slice.

The effects of the phorbol ester 4 beta-phorbol-12,13 dibutyrate (PDBu) and the protein kinase (PK) inhibitors H-7 and sphingosine were investigated on the short-term potentiation (STP) of the population excitatory postsynaptic potential (EPSP) induced by perfusion of N-methyl-D-aspartate (NMDA) in the stratum radiatum of CA1 of the rat hippocampal slice. Bath perfusion of 130 microM NMDA for 10 s caused an initial depression of the population EPSP followed by a STP, which averaged 46% and lasted 16 min. PDBu (100 nM) perfused for 2 h completely inhibited the NMDA induced STP, suggesting that the stimulation of PKC inhibited an NMDA receptor activated process which induced the STP. The protein kinase inhibitors H-7 and sphingosine did not alter the NMDA induced STP.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1991

The effects of external calcium on the N-methyl-D-aspartate induced short-term potentiation in the rat hippocampal slice.

The effect of altered extracellular Ca concentration was studied on the N-methyl-D-aspartate (NMDA) induced short-term potentiation (STP) of the population excitatory post-synaptic potential recorded from the stratum radiatum of CA1 of the rat hippocampal slice. Perfusion of 130 microM of NMDA for 10 s in control media containing 2.0 mM extracellular Ca evoked an STP with a maximum amplitude of 46% and a duration of 16 min. Perfusion of media containing a reduced Ca concentration of 0.8 mM or 1.0 mM did not alter the amplitude or time course of the STP. However, raising the Ca concentration to 3.0 mM or 4.0 mM caused a significant reduction in the amplitude of the STP to 23% and 2% respectively. The abolition of the NMDA induced STP in 4 mM Ca could not have been produced by response saturation since an identical long-term potentiation (LTP) was produced in this high Ca media as in the control media. These studies show that the NMDA induced STP has a very different Ca dependency to LTP.

Animals↗
PubMed1991

The effects of trans-ACPD on long-term potentiation in the rat hippocampal slice.

Trans-ACPD, a metabotropic glutamate receptor agonist, enhanced both the short-term potentiation (STP) at 1 and 5 min, and long-term potentiation (LTP) at 20 min, following tetanic stimulation, of the population, excitatory postsynaptic potential (epsp) recorded from CA1 of the rat hippocampal slice. The enhancement of both STP and LTP also occurred in the presence of the protein kinase inhibitor sphingosine, indicating that the enhancement is most likely to occur through the inositol phosphate rather than the protein kinase limb following receptor activation and phosphoinositide hydrolysis. LTP of the low frequency population epsp was not induced by t-ACPD, even at 100 microM. The metabotropic glutamate receptor may have an important role in LTP induction or modulation.

Animals↗
PubMed1991

Dandelion dermatitis.

7 subjects, each giving a history suggesting dandelion dermatitis, were patch tested with extracts of dandelion as well as with other common members of the Compositae and to the sesquiterpene-lactone-mix. All were positive to dandelion extracts but only 2 reacted to the sesquiterpene-lactone-mix. Although the mix is a useful screening test for chrysanthemum dermatitis, it may miss dandelion allergy.

Aged↗
PubMed1988

The role of calcium in short-term potentiation in the rat hippocampal slice.

Short-term potentiation of extracellular field excitatory postsynaptic potentials (EPSP's) was investigated in the stratum radiatum of CA1 of the rat hippocampal slice in vitro. A presynaptic tetanus consisting of a single train of stimuli at 250 Hz evoked short-term potentiation (STP), but not long-term potentiation (LTP) of small amplitude, just suprathreshold, EPSP's in a medium containing 2 mM Ca and 2 mM Mg. Increasing the number of stimuli in the tetanus enhanced the initial amplitude of the STP to a maximum of 40-70% with 30-40 stimuli, and enhanced the decay time constant of STP to a maximum of 60-80 s. Increasing the Ca influx by raising external Ca, lowering Mg or adding the agent 4-aminopyridine caused a large increase in the initial amplitude of STP but only a very slight increase in the decay time of STP. LTP was frequently evoked in high Ca/Mg ratios of 2.0 or 4.0, but not in 1.0 or 0.5.

Action Potentials↗
PubMed1988

The effects of external calcium on long-term potentiation in the rat hippocampal slice.

Extracellular excitatory postsynaptic potentials (EPSPs) were recorded from the stratum radiatum of CA1 of the rat hippocampal slice. The effect of altering the external Ca concentration was studied on the amplitude of the low frequency evoked EPSP preceding and following the production of long-term potentiation (LTP). The double logarithmic plot of the relationship between the EPSP amplitude and external Ca had a maximum slope of 2.1, implying Ca cooperativity in transmitter release. The production of LTP did not alter the slope. The amplitude of LTP was found to be highly dependent on the external Ca concentration, with LTP increasing from a 5% increase in the EPSP amplitude in 0.8 mM Ca, to a 65% increase in the EPSP amplitude in 2.0 mM Ca.

Animals↗
PubMed1987

Electroconvulsive treatment reduces long-term potentiation in rat hippocampus.

The effect of repeated electroconvulsive treatment (ECT) was investigated on long-term potentiation (LTP) in the rat hippocampal slice. Extracellular, recordings of population spikes and excitatory postsynaptic potentials (EPSP) were made from the pyramidal cell layer of CA1 in response to stimulation of the stratum radiatum. LTP was induced by 5 high-frequency trains of stimuli. ECT (10 treatments, 1 treatment every day for 20 days) markedly inhibited LTP of the population spike and EPSP. Thus LTP of the 25% maximum population spike was 104% in control, and 20% in rats 24 h after ECT. LTP of the EPSP was 35% in control and 12% after ECT.

Animals↗
PubMed1987

Caffeine inhibits post-tetanic potentiation but does not alter long-term potentiation in the rat hippocampal slice.

The effects of caffeine were investigated on the extracellular excitatory postsynaptic potentials (EPSPs) recorded in the stratum radiatum of CA1 of the rat hippocampal slice in response to stimulation of the Schaffer collaterals. Caffeine in concentrations from 500 microM to 10 mM caused an increase in the amplitude of the EPSP, which reached a peak after 5-10 min perfusion. This increase was antagonized by pretreatment with 20 microM trifluoperazine. Paired-pulse facilitation, augmentation and potentiation were strongly inhibited by caffeine. Augmentation was most sensitive to caffeine, being abolished by 500 microM caffeine. Long-term potentiation (LTP) induced by high-frequency stimulation was not significantly inhibited by caffeine either by 5-10 min or by 60 min perfusion with 10 mM caffeine. Moreover, the caffeine-induced increase in the low-frequency EPSP could be reversed by 30 min washout, demonstrating that it was not an LTP type increase.

Afferent Pathways↗
PubMed1986

4-Aminopyridine-mediated increase in long-term potentiation in CA1 of the rat hippocampus.

The effect of 4-aminopyridine (4-AP) on long-term potentiation (LTP) was studied in the hippocampal slice preparation of the rat. Field excitatory postsynaptic potentials (EPSPs) were recorded and evoked in the stratum radiatum of the CA1. Both the low frequency EPSP and LTP of the EPSP were significantly increased by treatment with 4-AP. These effects were inhibited by increasing the magnesium concentration from 1 to 4 mM. Pretreatment with 20 microM DL-2-amino-5-phosphonovalerate antagonized only the increase in LTP produced by 4-AP. It is suggested that 4-AP enhances Ca influx either pre- or postsynaptically and thereby increases LTP.

4-Aminopyridine↗