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Biomedical subjects

Y Lamour

Publications and source records attributed to Y Lamour.

At least 127 records · Page 7Linked to original sources
PubMed1981

[Laminar distribution of excitatory responses to acetylcholine in rat somatic sensory cortex: a microionophoretic study].

The laminar distribution of excitatory responses to iontophoretically applied acetylcholine (ACh) was studied in the first somatic sensory cortex (SI) of the Rat, using extracellular dye deposits for reconstruction of the electrode tracks. Most of the responses were recorded from neurons located in the lower half of the cortex, namely in layers V and VI. ACh sensitive neurons were found in two locations: one encompassing layer V and upper part of VI and the other at the border between cortex and white matter. The functional significance of this distribution is discussed.

Acetylcholine↗
PubMed1979

Thyrotropin-releasing hormone selectively depresses glutamate excitation of cerebral cortical neurons.

The microiontophoretic application of thyrotropin-releasing hormone causes a selective reduction in neuronal excitation evoked by L-glutamate but not by acetylcholine in rat cerebral cortex. Thyrotropin-releasing hormone has no influence on the activity of acetylcholinesterase or on choline uptake and release from cerebral synaptosomes. This evidence for a selective interaction between a centrally acting peptide and an excitatory amino acid neurotransmitter may indicate a specific locus of thyrotropin-releasing hormone action at glutamate-activated receptor sites.

Acetylcholine↗
PubMed1979

Effects of some divalent cations on motoneurones in cats.

In cats under Dial, Co, Mn, La, and Sr were injected extracellularly near lumbosacral motoneurones. All tended to improve intracellular recording, but when the membrane potential was initially stable, Mn, and especially Co, had a moderate and reproducible depolarizing action. Both Mn and Co depressed excitatory postsynaptic potentials evoked by dorsal root stimulation. The prominent after-hyperpolarization (a.h.p.), which normally follows the motoneuronal action potential, was consistently and reversibly depressed by Mn and Co (as well as La), the underlying conductance increase being also diminished, but there was no significant reduction in the after-depolarization. By contrast, Sr tended to potentiate the a.h.p., especially when this was depressed by a previous injection of Co or Mn. Unlike the other cations, Co had a marked depressant effect on the action potential, particularly its rate of rise. Since the action potential could be immediately restored by hyperpolarization or by an injection of Sr (in the absence of depolarization), Co may enhance Na inactivation.

Action Potentials↗
PubMed1979

Intracellular divalent cations and neuronal excitability.

Itracellular injections of Mg into cat spinal motoneurones have a depolarizing action, associated with a fall in input conductance, and depression of the postspike hyperpolarizing after-potential (a.h.p.) as well as its underlying conductance increase. There is also an increase in excitability, sometimes leading to outright discharge, and a change in the current-firing relation: the normal primary range is largely abolished and the firing appears to have the characteristics of the normal secondary range. Intracellular effects of Mg are thus mainly opposite to those of Ca, possibly owing to competition at sites where Ca activates K channels. Intracellular injections of Mn also tend to depress the a.h.p. but have relatively little effect on resting potential and conductance, or action potentials. Co also depresses the a.h.p. but has a more pronounced depolarizing action, and produces particularly strong depression of action potentials. By contrast intracellular Sr tends to raise the membrane conductance and has a mild hyperpolarizing effect. During the injection of Sr, a.h.p's are depressed but this is followed by a rebound of increased a.h.p. amplitude and conductance. Unlike the other divalent cations tested, Sr strongly depressed excitatory postsynaptic potentials. In most respects Sr appears to behave like Ca.

Action Potentials↗
PubMed1978

Motoneuronal after-potentials and extracellular divalent cations.

In cats under Dial anesthesia, microiontophoretic injections of Co2+ or Mn2+ outside lumbosacral motoneurones regularly diminish the postspike hyperpolarizing after-potential (AHP) without any clear reduction of the deplorarizing after-potential (ADP). Comparable injections of Sr2+ have the opposite effect of augmenting the AHP. These results indicate that the AHP is indeed initiated by an influx of calcium linked to the action potential, but the ADP is unlikely to be mainly a manifestation of a calcium inward current.

Action Potentials↗
PubMed1978

Intracellular actions of monoamine transmitters.

Intracellular injections of noradrenaline or dopamine in spinal motoneurones of cats have a clear depolarizing action associated with particularly marked depression of spike potentials and their after-hyperpolarization, but with little slowing-down of the falling phase of the action potential. These effects are associated with an increase in input resistance, and they are reversible and reproducible in the same neurone. Intracellular injections of 5-hydroxytryptamine have some depolarizing action and increased input resistance, but they produced no comparable depression of the action potential and tended to enhance the after-potentials and increase excitability. It is concluded that changes in intracellular levels of monoamines, whether physiological or drug induced, may be of significance for central neuronal function.

Action Potentials↗
PubMed1975

[Electrophysiological study of the blinking reflex of Macacus cynomolgus].

An electromyographic study of the blink reflex has been undertaken in the monkey Macacus cynomolgus. Reflex responses were evoked by stimulating trigeminal or facial afferent pathways and their modifications studied when a conditioning stimulus was applied to other afferences. The response may have two components (R1 = short latency, R2 = long latency) but R1 was only present after stimulating the ipsilateral supra-orbital nerve, whereas R2 alone occurred when either facial or contralateral supra-orbital nerves were stimulated. Previous stimulations of facial or contralateral supra-orbital nerves resulted in a facilitation of the reflex followed by some inhibition of R1 and R2 which became complete when the time interval was sufficient. The responses were depressed from 5 c/s (R1) or 2 c/s (R2).

Animals↗
PubMed1975

[Electrophysiological analysis of facial reflex in monkeys: trigemino-naso-labial reflex].

Electrical stimulation of the awake monkey's supra orbital nerve, elicits two successive reflex discharge in both naso-labialis muscles (NL). The responses have a similar high threshold. Similar responses are also elicited on electrical stimulation of the facial skin, whereas flash, click or tapping on the muscle belly are ineffective. These responses bear some resemblances to those obtained in orbicularis oculi muscles ; but the higher threshold and the different organization of the NL responses would suggest that such reflexes may serve a different function from that of the blink reflex.

Animals↗