The effects of systemic administration of selective antagonists of dopamine D1 and D2/D3 receptors on food-related and defensive (escape responses) conditioned paw-placing responses in cats.

Experiments were performed on cats to study the effects of systemic administration of antagonists of dopaminergic transmission on food-related and defensive (an escape response) operant conditioned reflexes acquired on the basis of the innate response of placing the forepaw on a support. Selective blockade of D1 receptors with SCH23390 (0.005-0.1 mg/kg) completely and selective blockade of D2/D3 receptors with raclopride (0.1-0.25 mg/kg) partially suppressed both reflexes. At these doses, both blockers had stronger actions on the defensive conditioned escape reflex than the food-related reflex: SCH23390 had significantly stronger inhibitory effects on both reflexes than raclopride.

Instrumentalization of movements evoked by stimulation of the motor cortex by food reinforcement in dogs.

The possibility that hindlimb movements (elevations) evoked by stimulation of the corresponding contralateral area of the motor cortex could be instrumentalized by reinforcement with food was demonstrated, contradicting some previously published data. Operant movements (interstimulus voluntary high elevations of the hindlimb) were acquired as a result of consistent combinations: cortical stimulation - movement - food. Acquisition required more than 50-200 combinations. Delivery of food was accompanied by a click at exactly the moment at which the hindlimb reached the required height. The click became the food-related conditioned signal and served as a secondary operant reinforcement, which facilitated acquisition of the operant movement. These results support the view that the motor cortex can have an immediate role in forming "operant" temporary connections (motivation-movement) and that simple operant movements can be initiated via this arc.

Somatosensory evoked potentials during natural and learning rearrangements of posture accompanied by limb elevation in dogs.

Changes in the functional state of the sensorimotor cortex associated with reorganization of the natural pattern of postural rearrangement before limb elevation (the "diagonal" patten and of an artificial rearrangement (the "unilateral" pattern) were studied in dogs. The state of cortical structures on postural rearrangement was assessed in terms of the pattern of somatosensory evoked potentials produced in response to stimulation of the forelimb during postural preparation of the animal for elevating the hindlimb (acquired avoidance response to a sound signal). Evoked potentials during the natural postural preparation (the "diagonal" pattern) were compared with those during the altered pattern of postural preparation (the "unilateral" pattern), this preparation taking place prior to elevation of the limb. Controls consisted of evoked potentials in the resting state. Decreases were seen in the latencies and amplitudes of most components of evoked potentials during postural rearrangement. In general, changes in evoked potentials were less marked in the "unilateral" pattern than in the "diagonal" pattern, though the differences were significant only for the amplitude of the first negative component. Changes in evoked potentials were similar regardless of whether the supporting forces of the limb to which the test stimulus was applied increased or decreased during postural rearrangement. It is suggested that differences in evoked potentials may reflect changes in the interaction between neuronal populations within the sensorimotor cortex during reorganization of the pattern of postural rearrangement associated with learning.

[Instrumentalization of movements induced by stimulation of motor cortex with food reinforcement in dogs]. / Instrumentalizatsiia dvizhenii, vyzvannykh stimuliatsiei motornoi kory, pri pishchevom podkreplenii u sobak.

Contrary to some literature data, the possibility to instrumentalize the movements (liftings) of the hind limb elicited by stimulation of the corresponding contralateral area of the motor cortex was shown. The instrumental reflex (spontaneous high lifting of the hind limb) was acquired after a number of uniform trials: cortical stimulation--movement--food. Food delivery was preceded by a click, which was presented during the hind limb lifting and served as a secondary reinforcement. The acquisition was rather prolonged (50-200 trials) and demanded some special conditions. The results count in favor of the viewpoint that the motor cortex can directly participate in establishing the instrumental conditioned connection (motivation--movement), and simple instrumental movements can be initiated through this connection.

[Natural coordination of the head and limb movements and its transformation by learning in dogs]. / Estestvennaia koordinatsiia dvizhenii golovy i lapy u sobak i ee peredelka v protsesse obucheniia.

Kinematic analysis of the head and the forelimb movements in dogs has been done during elaboration the instrumental tonic forelimb flexion when the head was bent down to foodwell. It was found, that in naive dogs the forelimb flexion was accompanied by anticipatory lifting of the head, the head lowering evoked extension of the flexed forelimb. Therefore simultaneous holding of the lifted limb and the lowered head was impossible and could be achieved only by learning. Studying of the dynamics of transformation of the innate (natural) head-forelimb coordination during learning has shown that innate relationship between phasic head-forelimb movements, which was lost at the early stage could spontaneously restore for a short time in trained dogs. It was found between low-amplitude head-forelimb oscillations which did not disturb the learnt tonic forelimb flexion, when the head was bent down. The innate coordination is supposed to be an inborn and in the given conditions the only possible way of the forelimb lifting, in which the anticipatory lifting of the head might facilitate the limb flexion. That's why lowering of the head provoked extension of the flexed limb. Contrary to the known hypothesis [4] that the mechanism of elaboration of the novel coordination is connected with suppression of the interfering innate coordination, it is proposed to consider the elaborated coordination as the novel way of the forelimb lifting in the forced posture of the lowered head. The novel flexion of the forelimb, as supposed, became possible by changing its innate organization (muscular pattern).

[Somatosensory evoked potentials during natural and learned patterns of postural adjustment, accompanying limb movements in dogs]. / Somatosensornye vyzvannye potentsialy vo vremia natural'noi i vyuchennoi perestroiki pozy, soprovozhdaiushchei pod''em konechnosti u sobak.

A goal of the study was to investigate cortical reorganization corresponding to inhibition of innate motor patterns during motor learning. Functional changes in the sensorimotor cortex during learned rearrangement of the natural diagonal pattern of postural adjustment (PA) accompanying a hindlimb movement into a new one, the so-called unilateral pattern, were studied in dogs by testing somatosensory evoked potentials (SEP) in response to stimulation of a forelimb during PA immediately before the limb movement onset. During PA the latency and the amplitude of several SEP components decreased. In general, changes in SEP were less pronounced in the learned unilateral pattern of postural adjustment in comparison with the innate diagonal pattern, but the difference was significant only for some SEP components. The SEP late positivity in the learned postural pattern was replaced by a negativity. The SEP changes were similar independently of whether the test stimulus was applied on the forelimb loaded or unloaded during postural adjustment. The data suggest that changes in interrelations between different neuronal populations in the sensorimotor cortex during formation and realization of a learned motor program can be reflected in SEP changes.

[A model of rat's urinary bladder tumor induced by subcutaneous injection of N-butyl-N-(4-hydroxybutyl)-nitrosamine]. / Model' opukholi mochevogo puzyria krysy pri podkozhnom vvedenii N-butil-N-(4-gidroksibutil)-nitrozamina.

A model of urinary bladder tumor was developed in the rat by subcutaneous injection of N-dibutyl-N-(4-hydroxybutyl) nitrosamine. A direct dose-tumor frequency correlation was established. Maximum effect (100%) was recorded with administration of 70 mg of the carcinogenic agent twice a week, for 3 months. Among neoplasms induced were transitional-cell and in situ carcinoma, and multiple papilloma of the bladder. Carcinogenesis was found to involve a significant rise in the activity of urinary beta-gluco-uronidase which may be used as a diagnostic testing procedure.

[The formation of instrumental escape reactions based on movements induced by stimulation of the motor cortex in dogs]. / Formirovanie instrumental'nykh reaktsii izbavleniia na osnove dvizhenii, vyzyvaemykh stimuliatsiei motornoi kory u sobak.

The purpose of the study was to find out the possibility of instrumentalization of movements induced by stimulation of the motor cortex (MI) in dogs. The scheme of conditioning was as follows. The electrical shock applied to the right forepaw was used for a weak painful stimulation. In 3 s, the stimulation of the MI was added, which elicited the right hind limb flexion. The shock was switched off at the moment of the hind limb lifting. After several trials, the shock began to elicit the hind limb flexion before the cortical stimulation. The scheme of conditioning excluded the possibility of instrumentalization of irrelevant chance movements. Prolonging the shock by 2 s after the cortical stimulation led to extinction of acquired responses. Renewal of reinforcement of the hind limb movements by immediate switching off the shock led to recovery of conditioned reactions. Thus, the instrumental nature of the responses has been proved. The obtained results are of particular interest in connection with the findings that similar acquisition of instrumental reaction on the basis of food reinforcement is impossible. The results support the assumption that the "instrumental" conditioned connection can be addressed directly to the motor cortex.

Varied influence of damage to the motor cortex on precision avoidance and escape reactions in dogs.

The influence of local extirpation of the representation of the forelimb in the motor area of the cortex on the performance of precision elevations of this limb was investigated. Even imprecise avoidance reactions to an acoustic signal did not recover spontaneously. Irregular motoric reactions which were insufficient in amplitude could easily be restored in the course of retraining, but precise movements (both rapid fused, as well as relatively slow stepwise movements) did not recover for at least a half year after the operation. By contrast with this, precise rapid reactions in response to electrical stimulation of a "working" limb (inducing unconditioned reflex flexion) remained essentially preserved, i.e., the capacity to stop the movement in the correct (previously learned) position of the limb was preserved. The capacity to fix the position of the raised limb was not lost, but was persistently impaired. The capacity to overcome the unconditioned reflex flexion during the performance of extensor "slow" escape reaction was reduced sharply and persistently. Limb presentation reactions regulated by vision were essentially spontaneously and nearly completely restored within a month.

[An experimental study of the tissue compatibility of titanium implants coated with hydroxyapatite and aluminum oxide by plasma spraying]. / Eksperimental'noe izuchenie tkanevoi sovmestimosti titanovykh implantatov, pokrytykh gidroksiapatitom i okis'iu aliuminiia putem plazmennogo napyleniia.

The reaction of bone tissue to implantation of cylindric titanium implants sprayed with hydroxyapatite and aluminum oxide was studied. The coating was characterized by a high biological histocompatibility. The elements of cellular reactions specific for foreign bodies were absent, this permitting us to refer such coating to bioactive materials. The strength of fixation in the bone was compatible to the strength of osseous tissue adjacent to bone tissue implant. The coating may be used in oral implantology, traumatology, and orthodontics.

The functional role of the motor area of the cortex in the formation of riddance reactions in dogs.

A model of instrumental conditioning similar to the classical model (Pavlovian) is proposed. Flexion of the ipsilateral forelimb was elicited while EDS was applied to the hind limb by stimulation of the motor area of the cortex (M1); both stimuli ceased during the raising of the forelimb. Uniform combinations of this kind led to the development of forepaw flexion reactions in response to the EDS of the hind paw. Prolongation of EDS by 3 sec following cortical stimulation led to rapid extinction of the developed reactions. Thus, the possibility of the effective instrumentalization of movements induced by stimulation of the M1 is proven. This argues that the forming "instrumental" connection (drive-motor structures) is addressed directly to the M1.

[The differential effect of damage to the motor cortex on the precise reactions of avoidance and escape in dogs]. / Razlichnoe vliianie povrezhdeniia motornoi oblasti kory na tochnostnye reaktsii izbeganiia i izbavleniia u sobak.

Effects of ablation of the forelimb area in the motor cortex on the precise lifting of this limb were studied. Even inaccurate avoidance reactions to the sound signal did not recover spontaneously. In the course of retraining irregular reactions of insufficient amplitude could be easily recovered but the precise reactions (both fast continuous and slow discontinuous) did not recover at least for half a year after the ablation. On the contrary, the fast precise escape reactions (to the shock applied to the "working" limb and eliciting its unconditioned flexion) remained essentially unchanged, i. a. the ability to stop movement in the correct (previously learnt) position persisted. The ability to fix position of the flexed limb retained but in was less perfect and did not improve. The ability to overcome unconditioned flexion (in order to perform discontinuous extensor escape reaction) was severely and continuously (for a year) decreased. Visually guided placings of the forepaw on a held out hand of an experimenter recovered essentially spontaneously and almost completely during a month.

[The functional role of the motor area of the cortex in the acquisition of escape reactions in dogs]. / Issledovanie funktsional'noi roli motornoi oblasti kory v formirovanii reaktsii izbavleniia u sobak.

The model of escape conditioning similar to classical (pavlovian) was proposed. During shock application to the hind limb (a conditioned stimulus) the ipsilateral foreleg flexion was elicited by a stimulation of the motor cortex (an unconditioned stimulus); both stimuli were turned off in the course of the forepaw lifting. Such uniform pairings resulted in elaboration of a reaction of the foreleg flexion in response to the shock. Prolonging the shock by 3 s after the cortical stimulation led to a rapid extinction of the acquired response. So a possibility to instrumentalize movements elicited by stimulation of the motor cortex (MI) was proved. This is in argument in favour of an assumption that the established "instrumental" connection (drive-motor structures) can be addressed directly to the motor cortex.

[The lithium carbonate promotion of urothelial tumors in rats induced with N-butyl-N-(4-hydroxybutyl)-nitrosamine]. / Promotsiia karbonatom litiia urotelial'nykh opukholei u krys, indutsirovannykh N-butil-N-(4-gidrokisbutil)-nitrozaminom.

The effect of lithium carbonate on promotion of N-butyl-N-(4-hydroxybutyl)-nitrosamine-induced bladder tumors in rats was studied. Lithium carbonate acted as promoter in bladder carcinogenesis resulting in a 6-fold increase in the tumor occurrence as compared to controls. The experiments with sequential injection of the agent showed its promoting effect to be most apparent within 3-6 months following exposure to the carcinogen.

[Sodium nitrate as a possible promotor of bladder carcinogenesis in rats]. / Natriia nitrat kak vozmozhnyi promotor kantserogeneza mochevogo puzyria u krys.

The effect of sodium nitrite on promotion of N-butyl-N-(4-hydroxybutyl)-nitrosamine-induced tumors of the bladder in rats was studied. Sodium nitrite was found to promote bladder carcinogenesis, raising the occurrence of carcinomas threefold as compared to controls.

[The effect of sodium selenite on the butyl butanol nitrosamine induction of bladder tumors in rats]. / Vliianie natriia selenita na induktsiiu butilbutanolnitrozaminom opukholei mochevogo puzyria u krys.

The study revealed the inhibitory effect of sodium selenite on induction of bladder cancer by butylbutanolnitrosamine in rats. The incidence of carcinoma in the control group was 87.5% whereas in the sodium selenite group--50% (P less than 0.01).

[Effects of forced diuresis on butylbutanolnitrosamine induction of bladder tumors in rats]. / Vliianie forsirovannogo diureza na induktsiiu opukholei mochevogo puzyria u krys butilbutanolnitrozaminom.

The study was concerned with the effect of forced diuresis on the frequency and morphologic pattern of bladder cancer induced with butylbutanolnitrosamine in rats. An 1.6 times increase in diuresis was followed by inhibition of bladder carcinogenesis, resulting in a 2.5-fold decrease in the tumor rate as compared to controls. The data obtained confirm the earlier suggested hypothesis of "urothelial contact" as well as epidemiologic data.

[The dynamic changes in somatosensory input into the cortical motor area after damage to the somatosensory cortical zones in dogs]. / Dinamika izmenenii somatosensornogo vkhoda v motornuiu oblast' kory posle povrezhdeniia somatosensornykh korkovykh zon u sobak.

Dynamics of changes in the somatosensory evoked potentials (EPs) in the foreleg motor cortex (MI) was studied in awake dogs in chronic experiments following lesions of the forelimb area in the somatosensory cortex (SI) or in area 5. Cortical ablations reduced the amplitude of the primary positive-negative wave of the EPs in ipsilateral MI down to 28-63% of the original one. Within three weeks recovery of the EPs was insignificant or was absent at all. So there was no correlation between the EPs changes and spontaneous recovery of precise avoidance movements of the foreleg which takes place two weeks after local ablation of the SI. After area 5 lesion the EPs in the MI did not recover in spite of complete recovery of the EPs in the adjoining area of SI after its initial reduction down to 53%. The long-lasting EPs reduction was apparently a result of destruction of somatotopic sensory inputs from SI (or area 5) to MI, since EPs in MI of the intact hemisphere and in the hindlimb area of MI on the side of the lesion either did not change or recovered during one or two weeks.