[Study of the activity of receptors with nonmyelinated fibers during heat exposure of the hairy cat skin]. / Issledovanie aktivnosti retseptorov s bezmielinovymi voloknami pri nagrevanii volosistoi kozhi koshki.

A nerve activity in heating of the cat hairy skin was studied in acute experiments in order to find out if the C-receptors take part in peripheral coding of heat information. An integrative cross-correlation technique was used to analyse neurograms in the real time. No C-afferent activity was found in the thermal stimulation up to 41 degrees C of the hairy skin.

[An analysis of the afferent flows from the glabrous skin receptors of cat foot pads during thermomechanical effects]. / Analiz afferentnykh potokov ot retseptorov goloi kozhi podushechek lap koshki pri mekhanotemperaturnykh vozdeistviiakh.

Cooling of the cat paw skin augmented the afferent activity in the n.n. plantaris whereas warning of the paws exerted an opposite affect. The code of thermomechanical sensory signals depended on the physical-mechanical condition of the skin.

[The activity of myelinated nerve fibers to heat and burn exposures of the skin]. / Aktivnost' mielinizirovannykh volokon pri teplovom i ozhogovom vozdeistviiakh na kozhu.

Activity of myelinated fibres in the n. saphenus was investigated by the crosscorrelation method in the cat's skin stimulated by heat and burn. The decrease of the total nerve activity under the heat action is proved to be related mostly to a change in A beta-fibres. It is shown that pain caused by heating of the skin over 42 degrees C activated A delta-fibres. The results obtained permit solving the problem of the heat information code from the view-point of the flow "pattern" theory.

[Pathways of nociceptive information transmission from different parts of the skin on cat paws]. / Issledovanie putei peredachi notsitseptivnoi informatsii ot razlichnykh uchastkov kozhi lap koshki.

Nociceptive reactions for damage and week actions on hairless and hairy skin was studied in acute experiments on cats. The damage stimulation of the hairless skin did not result in nociceptive reflexes, and in the case of hairy skin it always did. Using a cross-correlation method, some quantitative characteristics of afferent impulse discharges in the nerve plantaris of the cat were obtained under exposure damage and weak stimuli on the hairy and hairless skin. The afferent flow from the hairy skin has the C-afferent activity whereas in the case of hairless skin this activity was not observed. Peripheral coding of nociceptive signals under the damage action on pads of the cat is, obviously, impossible due to the absence of the C-afferent system in this kind of the hairless skin.

[Spike discharges from skin receptors during cooling]. / Issledovanie impul'snykh potokov ot retseptorov kozhi pri ee okhlazhdenii.

Using a crosscorrelation method some quantitative characteristics of afferent impulse discharges in the n. saphenus of cat were obtained during skin cooling. A 10 degrees C drop in the skin temperature at different cooling gradients caused activity in the A beta-, A sigma- and C-fibres. The C-fibres were activated first, than A delta-, A beta- and the quick-conductive A beta-groups successively. The latent period of the escitation of the C-fibres remained constant at different cooling rates of the skin, while for the A-fibres it increased with slowing down of the temperature drop rate. Both in A- and C-fibres the level of the maximum activity did not depend on the gradient of the skin cooling. But in all the mentioned groups of the fibres the starting time of the maximum activity decreased with the rise in the cooling rate.

Afferent flow patterns in a cat cutaneous nerve during painful and painless mechanical stimulation of the skin.

Quantitative characteristics of afferent flows coding information from a number of receptors were obtained by the gliding impulses method. The frequency spectrum of activity in a cutaneous nerve, the relative numbers of active Abeta, Adelta, and C fibers and their distribution by impulse transition frequency during stimulation of the cat's skin with pins and needles were determined. The afferent flow recorded in the nerve during pricking of the skin is characterized by high density, due to the number of excited fibers and the frequency of activity in them. The higher density of the afferent flow during the application of a painful than of a painless stimulus is mainly due to activity in C fibers. Unmyelinated fibers subjected to the action of the same stimulus and of chemically active substances liberated from the cells during tissue injury are excited directly and generate high-frequency spikes which increase the flow density in the nerve. The number of active myelinated fibers and the spike frequency during the action of a painful stimulus are only a little greater than the corresponding characteristics of the afferent discharge during painless stimulation.

[Impulse flow structure following exposure of a cutaneous nerve to nociceptive solutions of potassium chloride]. / Struktura impul'snogo potoka pri deistvii notsitseptivnykh rastvorov khloristogo kaliia na kozhnyi nerv koshki.

Using the cross-correlation method, the pattern of impulses flow coding a nociceptive signal is studied in the n. saphenus of the cat. It is found that nociceptive solutions of KCl (125-1000 mM) stimulate both myelinated and nonmyelinated fibres. The flow density increases with time of the stimulation action, reaching a level sufficient for the appearance of nociceptive pressure reflexes. The maximum of these reflexes coincides with the appearance of synchronous pulsations in the group of non-myelinated fibres. Thus a nociceptive signal caused directly by the exposure of the nerve to strong solutions of KCl is coded by a high density of the impulse flow, in which synchronous pulsations are likely to be found.

[Several characteristics of afferent flow following skin injuries]. / Nekotorye kharakteristiki afferentnogo potoka pri povrezhdaiushchikh vozdeistviiakh na kozhu

Using a crosscorrelation method, the quantitative characteristics of afferent impulse flow in the n. saphenus were investigated under stimulation of cat's skin with acid, needles, and pins. The appearance of the nociceptive reaction served as a noxious stimulation test. Noxious mechanical and chemical stimuli affecting directly the nerve fibres activate the same afferent fibres as those activated by weak tactile ones exciting the receptors. The impulse flows under such conditions differ by the amount of active A and C fibres, their correlation and the activity duration in them. The nociceptive reaction is realized owing to a considerable predominance of activity in C fibres over that in A fibres and owing to the long activity duration in both kinds of fibres, particularly in C fibres. The paper demonstrates the possibility to use an optic correlometer for the analysis of the activity in a whole nerve.

Analysis of activity in A and C fibres under mechanical and thermal stimulation of the skin receptor field.

A conduction velocity spectrum in nerve fibres of 0.15 to 90 m/sec was found by means of electrophysiological methods of analysis and computer-aided processing of experimental data. A greater portion of the non-myelinated fibres in the cutaneous nerve proved to be afferent. Patterns of afferent impulse flows entering the central nervous system are determined under various mechanical and thermal stimulations of cat's cutaneous receptive field. Differences of these flows are considered to be the reasons for various sensation modalities. The mechanism of cutaneous mechanoreceptor excitation under temperature stimuli is discussed. Special attention is paid to the contraction of cutaneous collagen under cooling. Experimental data on the change of cutaneous mechanical properties and the electrophysiological changes corroborating the thermomechanical hypothesis of receptor excitation are given.