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Biomedical subjects

R S Arutiunian

Publications and source records attributed to R S Arutiunian.

At least 19 recordsLinked to original sources
PubMed2002

[Response of respiratory neurons of the medulla oblongata to the septum stimulation in hypoxia].

In the oxygen deficiency conditions, we studied influence of irritation of ventral (BNST), lateral (LSN) and medial (MSN) nuclei of the septum on the impulse activity of the bulbar respiratory neurons and on respiration. Phases of hypoxia were the model of experiment. In conditions of normal atmospheric pressure, the electrical stimulation of BNST, LSN and MSN nuclei of the septum exerted inhibiting as well as activating influence with the inhibiting influence prevailing. In difficult conditions of hypoxia (7.5-8 thousand meters) on the reduction of the impulse activity of neurons, stimulation of septum nucleuses induced uncharacteristic reactions of those neurons.

Action Potentials↗
PubMed1996

[The significance of motor activity in regulating the cholinergic sensitivity of cat muscle spindles].

Following a complete transection of the spinal cord at the Th12-L1, an augmented chemosensitivity of the nuclear bag and nuclear chain fibres was observed. The supersensitivity of the intrafusal fibres to subecholine was higher than to acetylcholine. The supersensitivity of the intrafusal muscle fibres against the background of intact anatomical projections suggests that the motor activity rather than axonal transport plays the leading role in regulation of the cholinergic sensitivity of intrafusal muscle fibres.

Acetylcholine↗
PubMed1990

[The role of axonal transport in regulating the chemosensitivity of muscle spindles in the cat].

The effects of acetylcholine, subecholine and succinylcholine on the afferent activity of the m.EDL muscle spindles were compared before and after suppression of axonal transport by colchicine (20 nM, 30 min). The colchicine increased cholinergic sensitivity of nuclear-bag fibres: i. a. administration of cholinergic substances at concentrations tenfold lower than in control animals, produced a sharp enhancement of afferent activity of the muscle spindles. The increase of chemosensitivity was maximal to Ach and less obvious for subecholine and succinylcholine. No increase of activity could be produced by cholinomimetics in afferents originating from nuclear-chain fibres either in control, or after suppression of axonal transport.

Acetylcholine↗
PubMed1987

[Effect of actinomycin D on the post-denervational changes of chemosensitivity in muscle spindles in the cat].

The effect of preliminary injection of the inhibitor of protein synthesis actinomycin D on development of extrajunctional cholinergic receptors in denervated intrafusal muscle in cats, was investigated. Chronic motor denervation of the soleus muscle (3-5 days after denervation) caused supersensitivity of intrafusal muscle fibres to acetylcholine (Ah), subecholine (SCh) and succinylcholine (Sh). Injections of actinomycin D prevented the supersensitivity, the latter being dependent on the synthesis of new cholinoreceptors and their incorporation in the extrajunctional region of intrafusal fibres.

Acetylcholine↗
PubMed1984

[Pharmacological actions on the activity of muscle spindles induced by electrostimulation of the pericruciate cortex in the cat].

In anesthetized cats, effects of a number of neuroactive substances on results of local electrical stimulation of the motor (field 4) and supplementory motor (field 6) cortex were studied in intra - and extrafusal elements of the foot flexors. Flaxedil in subparalytic doses blocked selectively the contractions of extrafusal fibers whereas facilitating effects on activity of muscle afferents from the fields 4 and 6 were preserved which attests a possibility of cortical regulation of the gamma-system irrespective of alpha-motoneurons. Nembutal (5 mg/kg) rapidly suppressed the cortico-fugal excitatory effects which was easily opposed by bemegride. Aminasine (3-5 micrograms/kg) completely and for a long time blocked the cortical-motoneuronal influences. The cortico-reticular projections, anatomically well developed in cats, are supposed to be an essential component of the systems originating in the field 4 and particularly field 6.

Animals↗
PubMed1983

[Modulation of the activity of muscle afferents during stimulation of the motor and premotor cortex in the cat].

Local stimulation of hind leg motor representation area within the cat postcruciate cortex (area 4) changed the afferent activity of muscle spindles in hindpad flexor muscles. The early cessation of background activity correlated with extrafusal muscle fibres contraction. After return of the muscle to initial length, a significant increase of afferent discharge was observed followed by recovery to the initial level. Stimulation of contra- and ipsilateral parts of precruciate cortex (area 6) evoked selective long-lasting facilitation with aftereffect without involving extrafusal muscle fibres. Similar changes, however less pronounced occurred in secondary endings. The independent action of areas 6 and 4 on muscle spindle activity indicates a specific role of area 6 in regulation of segmentary activity of the gamma-system.

Animals↗
PubMed1981

[Changes in the sensitivity of the muscle spindles of fast and slow-contracting muscle fibers following chronic deafferentation].

The activity of muscle spindles was investigated in fast (m. EDL) and slow (m. sol) muscles of the cat 2-5 weeks after chronic deefferentation. The spontaneous activity of spindles in both muscles remains unchanged. The background activity and activity in dynamic and static phases of stretching both in primary and in secondary endings was much in chronic denervated muscle than in control. This increase in spindle activity was more pronounced in the slow muscle.

Muscle Contraction↗
PubMed1978

[Responses to the spindles of "fast" and "slow" muscles to mechanical stimulation in the presence of hypokinesia].

The activity of muscle spindles was investigated in fast (extensor digitorum longus) and "slow" (soleus) muscles of the cat hind limb 2-5 weeks after immobilization. The spontaneous activity of spindles in both muscles remained unchanged. The background activity, the frequency of dynamic and static phases of stretching in primary as well as in secondary endings was much higher in immobilized muscle than in control. This increase in spindle activity was more pronounced in the "slow" muscle.

Animals↗
PubMed1978

[Functional state of muscle receptors in experimental hypocalcemia].

Removal of the parathyroid glands induced hypocalcemia in cats and sharply increased the spontaneous and the evoked activities of primary and secondary endings of muscle spindles. I. v. administration of calcium chloride diminished the firing rate in control and experimental animals both in the dynamic and the static phases of stretching. The increased activity of muscle spindles seems to be of major importance for the development of motor disturbances during the parathyroid insufficiency.

Animals↗
PubMed1976

[Effect of thyrotoxicosis on the activity of proprioceptors of the skeletal muscles].

A study was made of the influence of prolonged administration of the thyroid hormones on the pulse activity of the cat soleus muscle spindles. In the animals with thyrotoxicosis the response of the primary endings of the spindles on the continuously acting and sudden rapid extension proved to be considerably enhanced both during the dynamic and the static phase. The frequency of discharges of the secondary endings showed no significant changes. It is supported that the changes in the activity of the primary endings observed were connected with the disturbances in the metabolism of the muscle and also with its atrophy.

Animals↗
PubMed1976

[Responses of the muscle spindles of tenotomized and hypertrophied muscles to stretch and vibration].

Responses of primary and secondary endings of muscle spindles were studied after tenotomy and hypertrophy in the cat soleus muscles. Under constant load (100 g) background activity of primary endings in a control muscle was 17 +/- 1.5 imp/s. It did not change in hypertrophic muscle and increased after tenotomy to 26 +/- 1.5 imp/s. Responses of secondary endings did not change under the same conditions. The frequency of a response from primary and secondary endings of tenotomized and hypertrophic muscles were higher during dynamic and static phase of stretching as compared to response of normal muscle spindles. Primary endings of tenotomized and hypertrophic muscles were able to repeat vibration up to 200 Hz, while secondary endings responded only with some increase in the discharge frequency.

Animals↗