[Impulse activity of the rat medulla oblongata in response to stimulation of taste receptors and visceral chemoreceptors]. / Impul'snaia aktivnost' prodolgovatogo mozga krys v otvet na razdrazhenie vkusovykh retseptorov i vistseral'nykh khemoretseptorov.

The unit activity from the medulla oblongata was extracellularly recorded during stimulation of taste receptors and visceral chemoreceptors of small intestine with the solutions of hydrochloric acid and sodium chloride. Neurons responding to the chemical stimulation are at the caudal part of nucleus tractus solitarius. Responses of taste, viscerochemical and convergence units are tonic and their discharge rates are low. The ability for chemical stimulus graduation analysis characterizes each group of units. Increased concentration of the solutions in intestine brings about the increase in the number of viscerochemical neurons with inhibited background activity. This may be the index of satiation and serve as a starting link in the mechanism of food rejection.

[Physiological analysis of food motivation in experimentally induced water-salt imbalance]. / Fiziologicheskii analiz pishchevoi motivatsii v usloviiakh éksperimental'no vyzvannogo narusheniia vodno-solevogo balansa.

Internal or motivational factors and external or signal factors were assessed to determine their role in motor-food response during conditioning in cats and dogs. Under experimental water-salt dysbalance visceral signalling was shown to be an essential factor involved in a goal-directed response. In addition to dominant motivation, a conditioned food signal seems to be this factor. In search for neurophysiological correlates of food motivation, we studied responses of n. tractus solitaris in rats to adequate chemical stimulation of the tongue receptors and viscerochemoreceptors. 3 groups of neurons were distinguished: those responding to the stimulation of only one receptive zone (taste and viscerochemical neurons) and neurons responding to the stimulation of both receptive areas ("convergence" units). Under salt deprivation, threshold concentrations of salt for responses from n. solitaris decreased and the response from a convergence neuron to viscerochemical stimulation diminished following application of sodium chloride on the tongue receptor.

[Reactions of neurons of the vagal lobe of the carp medulla oblongata to stimulation of chemoreceptors of the skin surface, oral cavity and gills]. / Reaktsii neironov doli bluzhdaiushchego nerva prodolgovatogo mozga karpa na razdrazhenie khemoretseptorov kozhnoi poverkhnosti, rotovoi polosti i zhaber.

In the experiments on immobilized carps it was found that the units of the vagal lobe of medulla oblongata respond not only to the stimulation of the mouth cavity and gills, but of skin chemoreceptors as well. The units responding selectively to skin surface stimulation are less in number than those responding to stimulation of the two other receptive fields. There are significant differences between the changes in unit activity elicited by natural alimentary stimulus (extract from the food product) and by hydrochloric acid and sodium chloride. Comparison of neuronal responses to stimulation of skin chemoreceptors in vagal and facial lobes revealed a different role in processing afferent information from skin chemoreceptors.

[Instrumental conditioned reflexes to salt and acid stimuli in carp]. / Instrumental'nye uslovnye refleksy u karpov na solevye i kislotnye razdrazhiteli.

In experiments on unrestrained carps, a comparative study was made of the analysis of different concentrations of NaCl and HCl (starting with threshold ones) by means of instrumental conditioned reflexes, aimed at eliminating harmful chemical stuffs from water medium. Salt concentrations, in response to which the formation of a conditioned reflex is possible (3--9 mM) are by an order higher than those for the acid (0.3--0.85 mM). The intensity and duration of manifestation of the defensive conditioned reflex depend directly on the strength (concentration) of the chemical stimulus. Cessation of motor conditioned reaction providing for restoration of the optimal conditions of the surrounding takes place when initial concentration of the stimuli in experimental reservoir is reduced to values close to threshold ones, namely to about 2 mM for NaCl and to about 0.2 mM for HCl, i.e. to a minimal concentration compatible with normal vital activity. After extirpation of the forebrain, the fish lose the capacity for active elimination from the surroundings of both salt and acid components.

[Comparative characteristics of neuronal response in the vagus and facial nerve lobes of carp medulla oblongata to chemoreceptor stimulation]. / Sravnitel'naia kharakteristika reaktsii neironov dolei bluzhdaiushchego i litsevogo nervov prodolgovatogo mozga karpa na razdrazhenie khemoretseptorov.

The unit activity in the vagal lobe of medulla oblongata in response to stimulation of the mouth cavity and gills chemoreceptors with solutions of hydrochloric acid and sodium chloride was studied in immobilized carps and compared with those in the facial lobe in response to skin chemoreceptors stimulation. The firing rate in the vagal lobe is lower and the latent period is longer than in the facial lobe. The level of the chemical stimuli gradations analysis is different in two parts of the chemoreception primary centre. In the vagal lobe units responding to the impulses from both receptive fields as well as those responding selectively to stimulation either of the mouth cavity or the gills were found. Activity of a firing pattern was predominant in the vagal lobe units in response to stimulation with sodium chloride solutions.

[Relationship between the characteristics of the acid stimulus and the impulse activity of medulla oblongata neurons in Cyprinus carpio carp]. / Zavisimost' impul'snoi aktivnosti neironov prodolgovatogo mozga karpa Cyprinus carpio ot kharakteristik kislotnogo razdrazhitelia

In experiments on immobilized carps, by means of extracellular recordings, studies have been made of the neuronal activity of the facial lobe in the medulla evoked by stimulation of skin chemoreceptors of the mouth opening with hydrochloric and cytric acids. Responses of the neurons to these stimuli exhibit both similarities and differences. Composing across-neuron patterns, some aspects of coding of quality and intensity of chemical stimulus in fish were elucidated. Particularly it was shown that at low concentrations of acids, in neuronal coding of the stimuli the key role is played by qualitative peculiarities of the latter, but not by the level of pH.

[Evoked potentials in the optic tectum of the carp brain upon electric stimulation of the facial nerve]. / Vyzvannye potentsialy v kryshe srednego mozga karpa pri élektricheskom razdrazhenii litsevogo nerva

The evoked potentials in the carp tectum opticum in response to stimulation of the afferent pathway for chemical nonolfactory reception, the facial nerve, are positive deflections of 5-25 ms latency which do not reverse during microelectrode submersion. According to the evoked potential amplitude and latent period 7 active zones were distingnished in the ipsilateral tectum differing from each other either in one or in both parameters. The dependence of the response evoked by facial nerve stimulation in the tectum opticum on the impulsation from the medulla is proved by the difference in latency and by disappearance of the response in the tectum while persisting in the medulla after disconnection of both areas of the brain. The existence of efferent influences from the tectum upon the primary centre is suggested as the tectum ablation causes in some parts of the medulla either complete disappearance of the facial evoked potentials or changes in their parameters.