[Intensification of c-fos expression in the spinal cord initiated by the signals from fatigue skeletal muscles].

Immunohistochemical studies of c-fos expression in the lumbar and neck segments of spinal cord after fatiguing stimulation of the mm. gastrocnemius-soleus or m. trapezius and m. splenius, were carried out on the anaesthetized (chloral-hydrate 400 mg/kg, i.p.) rats. The patterns of the Fos-immunoreactive neurons distribution in the grey matter of spinal cord in the L4 and L5 segments, as well as the C2 and C3 were similar. The highest number of marked cells was registered in the dorsal horn in the first, fourth and fifth layers of grey matter, i.e. within the areas of termination of high-threshold muscle afferents of group III and IV. It is assumed, that the types of afferents could be activated by muscle fatigue-induced metabolites. The signals incoming to the spinal cord could be involved into the presynaptic inhibition of muscle spindle volleys than resulted in the impairment of motor output performance. This mechanism is substantial for limitation of the force of muscles contraction and prevention the injury of the muscles under the excessive physical loading.

[Systematic positioning errors and electromyographic activity of muscles in the human single-joint movements].

Accuracy of positioning was studied on the elbow joint movements in healthy adult humans. Individual trials consisted of the conditioning and test movements (CM, TM) produced with visual guidance and without it, correspondingly. The two types of CMs included a phase of slow movement (flexion - P1, or extension - P2) to the same target position (50 degrees in the most experiments). P1 and P2 CMs started, correspondingly, from the full extension position (0 degrees), or after preliminary flexion (100 degrees). Subjects were asked to remember the target position during CMs and to reproduce it in TM. The experiments have shown that position errors depend on the type of CMs. The subjects overestimated the target position, the errors were more significant in TMs produced after P2 CMs as compared with P1 CMs. Full-wave rectified, averaged EMGs were compared for the two types of CMs. In flexors the dynamic phases ofEMG activity were statistically greater in P1 than in P2 CMs (a group of 25 subjects), while the stationary components of EMG did not differ. Possible mechanisms of the position errors are discussed. It is suggested that after-effects in the activity of muscle spindles may be the main source for the position errors.

[Effects of experimental muscle pain on short and long-latency components of stretch-reflex in the elbow muscles of the unanaesthetized cat].

Electromyographic (EMG) activity of the elbow joint muscles induced during passive extension of the joint was recorded from the unaesthetized cat before and after injection of 5% NaCl solution which has been used as an activator of nociceptors. It was shown that the amplitude of the long-latency M2 component of flexor stretch-reflex was significantly increased after injection of saline while the amplitude change of shot-latency M1 component was insignificant. The latency of EMG in flexor significantly decreased. The changes of extensor EMG response parameters were similar but less expressed. Duration of such effect could achieve 20 minutes, after that all response parameters of stretch-reflex returned to the standard values.

[Effect of tonic painful squeezing of the finger distal joint on the evoked potential of different spectral frequency ranges in electroencephalogram of humans].

EEG changes caused by the tonic squeezing of the distal joint of the little finger of both hands were investigated on 12 healthy volunteers, age 20-56 (average 35.5). Pain stimulation applied to the right hand was stronger than that applied to the left. Power spectra was measured in 7 EEG ranges: delta--2-4, theta1--4-6, theta2--6-8, alpha1--8-10.5, alpha2--10.5-13, beta1--13-20 and beta2--20-35 Hz. The increase of power in the different areas of the cerebral cortex was a dominant effect of pain influence in beta1 and beta2 as well as in both alpha-ranges. The pain stimulation influenced EEG-parameters bilaterally. It was supposed that increment of alpha-synchronization during peripheral pain reflected the inhibition processes in the thalamo-cortical system. This process most likely limited the area of afferent activation in the cortex. The topography of the significant power changes in alpha1- and alpha2-ranges was different during strong pain as well as after its cessation. Different parameters of functional brain activity during pain stimulation seemed to be reflected in alpha1- and alpha2-rhythms. The significant increment of spectral power in alpha-, beta- and theta2-ranges was demonstrated after cessation of strong pain in comparison to the pre-pain condition. Thus, the changes in EEG parameters reflect the latent and inertial character of the pain effects.

[Central neuronal pathways in the Bezold-Jarisch reflex in rats].

The distribution of the Fos-immunoreactive (Fos-ir) and NADPH-diaphorase-positive/NOS-containing neurons in the medulla and thoracic spinal cord in rats was studied after the veratrine injection into v. jugularis ext. followed by reproduction of the Bezold-Jarisch reflex. Fos-ir neurons were found in the nucleus tractus solitarius (Sol), coudoventrolateral (CVL) and rostroventrolateral (RVL) areas, intermediate reticular nucleus (IRt), and lateral paragiganrocellular nucleus (LPGi) of the medulla. The intensity of c-fos expression was as follows: Sol > CVL > RVL > LPGi. The intensity of NADPH-diaphorase reactivity was manifested in the following sequence: Sol > IRt > LPGi > RVL. In comparison to sham-operated animals, application of veratrine is associated with a statistically significant increase (P < 0.01) of the mean number of Fos-ir neurons in the Sol and CVL, but not in the RVL. Double-labelling (Fos + NA DPH) was found in a small number (about 2%) of neurones in the Sol, IRt and LPGi. In the thoracic spinal cord Fos-ir neurons were predominantly detected in the superficial layers of the dorsal horn, area around the central canal and the intermediate lateral or medial nuclei (IMl and IMM), where NOS-containing neurons in the thoracic spinal cord were accumulated. Received data show that signals arising from the veratrine-activated cardiopulmonary afferents activate neurons of the Sol and CVL that together with the RVL are incorporated into neuronal circuits for generation of the Bezold-Jarisch reflex. In the medulla NOS-containing neurons activated by input from cardiopulmonary receptors can contribute to the enhancement of cardioprotective depressor reflexes in the rats.

[Effects of bradykinin and capsaicin intramuscular injections on stretch-evoked postsynaptic response of motoneurones of the gastrocnemius-soleus muscle].

Responses of gastrocnemius-soleus motoneurones to stretches of the homonymous muscles were recorded intracellularly in the decerebrated cats during intramuscular injections (IMI) of bradykinin or capsaicin into the muscles. Effects of IMI on EPSPs and spikes evoked by stretches of the G-S muscles were studied in 6 motoneurones. Stretch-evoked EPSPs and firing were predominantly suppressed after IMIs, with the exception of slight increase of EPSPs up to 150 s after bradykinin injection, followed by theirs distinct decrease. The suppression of spike activity was followed by restoration within 500-800 s after bradykinin injection. Stretch-evoked EPSPs and firing were depressed after capsaicin injection; control level of motoneurones activity was seemed to be unrecoverable for quite a long time. No background IPSPs were observed after algesic injections and presynaptic inhibition was considered as plausible reason for the observed suppression of motoneurones activity.

[Expression of c-fos in the spinal cord after electrical stimulation of low-threshold afferent fibres of the rat n. gastrocnemius-soleus]. / Ekspresiia c-fos u spynnomu mozku pislia elektrychnogo podraznennia nyz'koporohovykh aferentnykh volokon u skladi n. gastrocnemius-soleus shchura.

The specific pattern of c-fos gene expression was evaluated within the lumbo-sacral spinal cord during 30 min non-noxious stimulation n. gastrocnemius-soleus of male Wistar rats. A lot of small and large Fos-immunoreactive (Fos-ir) nuclei were located ipsilaterally, mainly in the middle of the neck and base of the dorsal horn (layers 5 and 6). Traditionally, these layers are considered to be the region of termination of the low-threshold afferent fibers. A few Fos-ir neurons were recorded in the intermediate zone (layer 7) and the area around central canal (layer 10). The scarce labeled cells were also revealed within the marginal zone and substantia gelatinosa of the dorsal horn, i. e. the zones of termination of the high-threshold muscle afferents. In conclusion, the revealed pattern of c-fos expression in the spinal cord following non-noxious stimulation differs from that induced by noxious stimulation. Thus, the pattern of c-fos expression in the spinal cord is dependent on the stimulus modality.

[Characteristics of distribution of nitric oxide synthase containing neurons in the medullary cardiovascular centers of dogs and rats]. / Osoblyvosti rozpodilu neironiv, shcho mistiat' syntazu oksydu azotu v meduliarnykh sertsevo-sudynnykh tsentrakh sobak i shchuriv.

The aim of the study was to characterize species-related differences in the distribution of nitric oxide synthase (NOS)-containing neurons in the medullary structures of dogs and rats involved in the regulation of the sympathetic or parasympathetic drives. Two main results have been obtained, namely: (i) the average number of NOS-containing neurons in the dorsomedial and ventrolateral medulla per section in dog was larger than that in rat, while the density of the positive cells in the both regions in dog was less than that in rat. (ii) Within the dorsal motor nucleus of vagus a lot of NOS-containing cells (preganglionic vagal neurons) were observed only in dog. Differences in the distribution of NO-generating neurons in the medullary cardiovascular centers, and heterogeneity in the basal level of NO release may contribute to the peculiarities of the hemodynamic responses induced by NOS inhibitors in these species.