[Endogenous opioid mechanisms in the regulation of pain sensitivity and behavioral reactivity in various aversive states]. / Endogennye opioidnye mekhanizmy v reguliatsii bolevoi chuvstvitel'nosti-povedencheskoi reaktivnosti pri aversivnykh sostoianiiakh razlichnoi prirody.

Study of the effect of naloxone that blocks opiate receptors on changes in thresholds of vocalization and latent periods of motile reaction in freely-behaving rats, at leg injury, intraperitoneal introduction of algogene, and at immobilization stress allowed to estimate the involvement of endogenous opiates in regulation of pain sensitivity and motile activity. Naloxone-weakened inhibition of vocalization is accompanied by the increase in inhibition of motile responses, characteristic for visceral pain and the absence of changes at trauma and immobilization stress suggest that opiates are involved in formation of endogenous analgesia at strong visceral pain stimulation.

[The pain sensitivity and behavioral reactivity of rats in somatic and visceral pain states]. / Bolevaia chuvstvitel'nost'-povedencheskaia reaktivnost' krys v usloviiakh somaticheskogo i vistseral'nogo bolevykh sostoianii.

The vocalization thresholds and latent periods of motile reaction have been studied in normal rats, at extremity trauma, and at intraperitoneal injection of an algogen [correction of allogene]. The dissociation of changes in pain sensitivity and motile reactivity in during, visceral and somatic pain conditions was observed. A strong hypoalgesia during visceral stimulation and hyperalgesia at trauma accompanied by inhibition of motile activity have been discussed from the point of view of their significance in defense reactions of the organism at pain conditions of various nature.

[Long-term enhancement of morphine hypalgesia as a result of periodic blockade of opiate receptors using naloxone]. / Dlitel'noe usilenie morfinovoi gipal'gezii kak resul'tat periodicheskoi blokady opiatnykh retseptorov naloksonom.

A significant enhancement of the analgetic effect of morphine (6 mg/kg, subcutaneously; tail withdrawal reflex at 60 degrees C) was observed in rats 3-4 hours after single naloxone (1 mg/kg) administration. Periodical naloxone injection (0.5 mg/kg, subcutaneously, 3 times per day at 3.5-hour intervals for 3 days) led to a prominent and long-term (testing on the 20th and 105th hour after the last naloxone administration) enhancement of morphine analgesia (2.6 mg/kg subcutaneously) and insignificant inhibition of stress analgesia during two-hour immobilization of animals. These modifications of morphine and stress analgetic effects are considered a result of adaptive changes of opiate receptors after their blockade.

[Effect of naloxone on hypoalgesia in rats exposed to prolonged immobilization stress]. / Vliianie naloksona na gipoalgeziiu u krys v usloviiakh dlitel'nogo immobilizatsionnogo stressa.

Significant hypoalgesia (tail-flick reflex at 60 degrees C) was observed in rats during the whole period of 24-hour immobilization in cramped cages, as compared to food-and-water deprived and control animals. This hypoalgesia was not antagonized by naloxone (1 mg/kg), however, the animals periodically receiving the drug during immobilization revealed aggressiveness and significant hypoalgesia after immobilization was discontinued (30-120 min observation).

[Spike activity of mesencephalic neurons during nociceptive stimulation of the alert cat]. / Impul'snaia aktivnost' mezentsefalicheskikh neironov pri notsitseptivnoi stimuliatsii u bodrstvuiushchikh krys.

Rate of reorganizations of neuronal impulse activity in the ventromedial parts of the midbrain of alert rats in conditions of nociceptive and non-nociceptive actions is determined by biological value of used stimuli and closely correlates with spontaneous and evoked changes of the motor activity and oscillations of vegetative parameters. The character of reorganizations of discharge activity (activation, inhibition) significantly differs in cells of various types, singled out on the basis of differences of electrophysiological properties and predominantly localized in different parts of the studied brain areas. The revealed characteristics of the functional properties of the neurones are discussed in connection with supposed differences of their neurotransmitter specificity and their role in providing for different chains of adaptive activity of the organism.

[Electrophysiologic properties of neurons of the ventral tegmentum of the midbrain of the alert rat]. / Elektrofiziologicheskie svoistva neironov ventral'noi pokryshki srednego mozga u bodrstvuiushchikh krys.

Statistical analysis of firing activity, spike shape and duration of single units in ventral tegmental area and adjacent regions of midbrain was performed in conscious rats. Four cell types were distinguished in this neuronal population which heterogeneity may be related to differences in their neurochemical nature and afferent connections.

[ACTH, corticosterone and beta-endorphin in the blood plasma of rats under prolonged immobilization stress]. / AKTG, kortikosteron i beta-éndorfin v plazme krovi krys v usloviiakh dlitel'nogo immobilizovannogo stressa.

Radioimmunoassays were employed to study variation in the concentration of corticosterone, ACTH and beta-endorphin in rat blood plasma at different times of the 30-hour immobilization and under the effect of a short-term action of ecologically significant negative stimulation emanating from other animals. Both prolonged immobilization stress and short-term emotional reaction produced appreciable alterations in the blood plasma content of all the hormones under study. The findings indicate that variations in the corticosterone and beta-endorphin levels were in the best agreement.

[Chemoreactive properties of medial thalamic neurons of the rat in the following states: urethane anesthesia, wakefulness and immobilization stress]. / Khemoreaktivnye svoistva neironov medial'nogo talamusa u krys v sostoianiiakh: uretanovogo narkoza, bodrstvovaniia i immobilizatsionnogo stressa.

An analysis was carried out by means of microelectrode records and microionophoresis of medial thalamus neurones chemical sensitivity to acetylcholine and noradrenaline in rats under urethane anaesthesia, in free behaviour and in immobilization stress. Significant differences were observed in stability of cellular responses to repeated application of mediators under these conditions and in the correlation of the cells with qualitatively different reactions to these mediators. Along with the functional state of the animals, probability and direction of "spontaneous" changes of neuronal chemoreactive properties significantly depended on the type of sensibility inherent in them at that moment.

[Spike activity of neurons of the medial thalamus of the rat during urethane anesthesia, wakefulness and immobilization stress]. / Impul'snaia aktivnost' neironov medial'nogo talamusa u krys pri uretanovom narkoze bodrstvovanii i immobilizatsionnom stresse.

A statistical analysis was carried out of unit activity in the medial thalamus (MT) of rats in states of urethane anaesthesia, quiet unrestrained wakefulness and immobilization stress. Discharge activity of MT neurones in these states significantly differed by parameters characterizing both single cells (mean frequency, standard deviation, variation coefficient) and their populations (intragroup variability of parameters, homogeneity of population as to the activity of its cells components, the extent of connections between them). The revealed differences are interpreted as a reflection of the properties of central interneuronal integration created in accordance with real needs of the organism for providing for its adaptive activity.

[Chemical sensitivity of neurons to immobilization emotional stress in the rat]. / Khimicheskaia chuvstvitel'nost' neironov k noradrenalinu pri immobilizatsionnom stresse u krys.

Chemical sensitivity of the neurones of the medial thalamus (MT) and ventromedial hypothalamus (VMH) to noradrenaline (NA) was studied microionophoretically in conditions of 30-hour immobilization of rats. Chemical sensitivity of single neurons of MT as well as VMH during immobilization is characterized by a certain instability, showed in changes of their reactions at repeated NA applications. These changes were observed significantly more frequently in MT neurones especially at the initial stage of immobilization. At the final stage as well as in unrestrained control animals, changes of the sensitivity were seen significantly more seldom. At the initial stage of rats' immobilization a significant increase of the number of MT and VMH cells responding to NA application by the excitative type of reactions was also observed.

[Mikroiontophoretic analysis of the interrelation between spike activity and chemical sensitivity of neurons of the medial thalamus to acetylcholine and noradrenaline in alert rats]. / Mikroionoforeticheskii analiz vzaimosviazi impul'snoi aktivnosti i khimicheskoi chuvstvitel'nosti neironov medial'nogo talamusa k atsetilkholinu i noradrenalinu u bodrstvuiushchikh krys.

An interconnection between spontaneous impulse activity of medial thalamus (MT) neurones and their chemical sensitivity to acetylcholine (ACh) and noradrenaline (NA) was revealed in rats by means of microelectrode recording and microionophoresis in conditions of free behaviour and during immobilization stress. The neurones with the most rare reactions (inhibitory to ACh and excitatory to NA) had higher frequency and variance of discharges in comparison to the cells with most typical responses (excitatory to ACh and inhibitory to NA). The number of cases with changed sensitivity of single units in these conditions directly correlated with the firing rate and variance of the unit discharges. Qualitative changes in cells' sensitivity to ACh and NA elicited in rats both "spontaneously" in conditions of immobilization stress and under the action of electrocutaneous stimulation were not always tightly connected with the observed phasic changes of their discharges.

[Statistical analysis of diencephalic neuronal spike activity during immobilization emotional stress in the rat]. / Statisticheskii analiz impul'snoi aktivnosti neironov mezhutochnogo mozga pir immobilizatsionnom émotsional'nom stresse u krys.

On the basis of one second frequency values of spike activity, a study was made of statistical parameters of impulse flow power of 64 dorsomedial thalamus (DMT) neurones, 180 ventromedial thalamus (VMT) neurones and 110 ventromedial hypothalamus (VMH) neurones in alert rats during a 30 hour immobilization. The VMH neurones had highly significant lower values of standard deviations and variation coefficients of spike activity frequencies as compared with medial thalamic neurones. In the two parts of the medial thalamus (DMT and VMT) the neuronal mean frequency and standard deviations of spike activity frequencies were significantly enhanced at the initial stage of the animals' immobilization as compared with the final stage. In the VMH neurones enhancement of the mean frequency without pronounced change of other parameters of impulse was observed at the final stage of immobilization due to the appearance of a group of high frequency neurones with low variability of the spike flow.