Reflection of the State of Hunger in Impulse Activity of Nose Wing Muscles and Upper Esophageal Sphincter during Search behavior in Rabbits.

Reflection of the state of hunger in impulse activity of nose wing muscles and upper esophageal sphincter muscles was studied in chronic experiments on rabbits subjected to 24-h food deprivation in the absence of locomotion and during search behavior. In the absence of apparent behavioral activity, including sniffing, alai nasi muscles of hungry rabbits constantly generated bursts of action potentials synchronous with breathing, while upper esophageal sphincter muscles exhibited regular aperiodic low-amplitude impulse activity of tonic type. Latent form of food motivation was reflected in the structure of temporal organization of impulse activity of alai nasi muscles in the form of bimodal distribution of interpulse intervals and in temporal structure of impulse activity of upper esophageal sphincter muscles in the form of monomodal distribution. The latent form of food motivation was manifested in the structure of temporal organization of periods of the action potentials burst-like rhythm, generated by alai nasi muscles, in the form of monomodal distribution, characterized by a high degree of dispersion of respiratory cycle periods. In the absence of physical activity hungry animals sporadically exhibited sniffing activity, manifested in the change from the burst-like impulse activity of alai nasi muscles to the single-burst activity type with bimodal distribution of interpulse intervals and monomodal distribution of the burst-like action potentials rhythm periods, the maximum of which was shifted towards lower values, which was the cause of increased respiratory rate. At the same time, the monomodal temporal structure of impulse activity of the upper esophageal sphincter muscles was not changed. With increasing food motivation in the process of search behavior temporal structure of periods of the burst-like action potentials rhythm, generated by alai nasi muscles, became similar to that observed during sniffing, not accompanied by animal's locomotion, which is typical for the increased respiratory rhythm frequency. Increased hunger motivation was reflected in the temporal structure of impulse activity of upper esophageal sphincter muscles in the form of a shift to lower values of the maximum of monomodal distribution of interpulse intervals on the histogram, resulting in higher impulse activity frequency. The simultaneous increase in the frequency of action potentials bursts generation by alai nasi muscles and regular impulse activity of upper esophageal sphincter muscles is a reliable criterion for enhanced food motivation during search behavior in rabbits.

Objective method for registration of the sniffing component of the search behavior in rabbits subjected to food deprivation.

A method for registration of the sniffing component of the search behavior in rabbits subjected to food deprivation is suggested. Pulsed activities of the muscles controlling the movements of the wings of the nostrils and the pressure in the nasal cavity are recorded simultaneously. The method allows accurate artifact-free registration of the time and amplitude parameters of the sniffing component of the search behavior. The registration is realized on an MP150 programmed complex, consisting of EMG 100C biopotential amplifiers and Samba 202 intracavitary pressure recorder. The method allows synchronous real-time registration of pulsed activities of the muscles setting in motion the wings of the nostrils and the changes in the intranasal pressure in the course of search behavior of animals under conditions of food deprivation without limiting their locomotor activity.

Effects of electric stimulation of the hunger center in the lateral hypothalamus on slow electric activity and spike activity of fundal and antral stomach muscles in rabbits under conditions of hunger and satiation.

In chronic experiments on rabbits, the effect of electric stimulation of the hunger center in the lateral hypothalamus on myoelectric activity of the fundal and antral parts of the stomach was studied under conditions of hunger and satiation in the absence of food. Stimulation of the lateral hypothalamus in rabbits subjected to 24-h food deprivation and in previously fed rabbits produced incessant seeking behavior, which was followed by reorganization of the structure of temporal organization of slow wave electric activity of muscles of the stomach body and antrum specific for hungry and satiated animals. Increased hunger motivation during electric stimulation of the lateral hypothalamus manifested in the structure of temporal organization of slow wave electric activity of the stomach body and antrum muscles in rabbits subjected to 24-h food deprivation in the replacement of bimodal distribution of slow wave periods to a trimodal type typical of 2-day deprivation, while transition from satiation to hunger caused by electric stimulation of the lateral hypothalamus was associated with a shift from monomodal distributions of slow wave periods to a bimodal type typical of 24-h deprivation. Reorganization of the structure of temporal organization of slow wave electric activity of the stomach body and antrum muscles during electric stimulation of the lateral hypothalamus was determined by descending inhibitory influences of food motivational excitation on activity of the myogenic pacemaker of the lesser curvature of the stomach.

[Influence of electrical stimulation of "hunger center" of the lateral hypothalamus and food reinforcements on myoelectrical activity of the gastro-esophageal sphincter and stomach in rabbits under the conditions of hunger and satiation].

AIM: To study the combined effect of electrostimulation of "hunger center" of the lateral hypothalamus (LH) and food-obtaining behavior arising from it on myoelectrical activity of gastro-esophageal sphincter (GES) and the stomach in pre-fed and subjected to food deprivation animals . MATERIAL AND METHODS. Registration of myoelectrical GES and the stomach activity was carried out under free-behavior conditions in rabbits subjected to food deprivation or pre-fed before the experiment. It was done by means of chronically implanted electrodes during LH electrostimulation in the presence of food. Simultaneously using the web-camera the animals behavior was recorded. LH stimulation was produced by STM-100C stimulator (USA) with implanted bipolar nichrome electrodes. Analysis of temporal parameters of myoelectrical activity of GES and the stomach were carried out by the program AcqKnowledge (USA), and statistical analysis of the data by the program Statistica 6. Significanse of differences between the samples was assessed by the U-Mann-Whitney test (p < 0.05). RESULTS: Electrostimulation of "hunger center" of the lateral hypothalamus in pre-fed rabbits and the rabbits subjected to daily food deprivation, in the presence of food causes resultant food behavior which is accompanied by regular generations of bursts of peak potentials, frequency of which is essentially different in hungry and satiated animals and depends on intensity of artificially induced and artificially reinforced food motivation. In the process of LH stimulation arising resultant food behavior in satiated animals is accompanied by regular generation of high-amplitude slow electrical waves (SEW) by the muscles of lesser curvature (LC), the body and antrum of the stomach (AS) and this is reflected in the structure of temporal organization of slow electrical activity (SEA) in the form of monomodal distributions of SEW periods, typical of satiation state. Despite the increase in food motivation level, due to LH stimulation, additional entry of food into the stomach of satiated rabbits completely eliminates inhibitory effect of starvational motivational excitation on SEA of the muscles of LC, the body and AS. SEA alterations of the stomach muscles in hungry rabbits in the presence of food and thus arising of food-obtaining behavior during LH stimulation have two-phase character. At the initial stage of food behavior in hungry animals during LH stimulation high extent of scaterring of the values of SEW periods generated by the body and AS muscles is preserved, as evidenced by the bimodal distribution of SEW periods characteristic of the state of hunger. In spite of food entry into the stomach at the 1-st phase of LH stimulation, inhibitory effect of artificially reinforced starvational motivational excitation on pacemaker activity of the stomach is retained. At the 2-nd phase of LH electrostimulation food reinforcement eliminates inhibitory effect of food motivational excitation on myoelectrical activity of pacemaker of the stomach that gives maximal rhythm of SEW generation to the body and AS, monomodal distributions of SEW periods indicate to it. CONCLUSION: lnteraction of artificially induced and artificially reinforced food motivational excitation with afferentation from food reinforcement on neurons of the central generator of deglutition pattern and dorsal vagal complex due to LH electrostimulation and thereby arising resultant food obtaining behavior is specifically reflected in patterns of myoelectrical activity of GES, LC, the body and AS.

Effects of electrical stimulation of the hunger center in the lateral hypothalamus and food reinforcement on impulse activity of the stomach in rabbits under conditions of hunger and satiation.

Stimulation of the lateral hypothalamus in preliminary fed animals in the presence of the food is associated with successful food-procuring behavior, accompanied by regular generation of high-amplitude slow electrical waves by muscles of the lesser curvature, body, and antrum of the stomach, which was reflected in the structure of temporal organization of slow electrical activity in the form of unimodal distribution of slow wave periods typical of satiation state. Despite increased level of food motivation caused by stimulation of the lateral hypothalamus, the additional food intake completely abolished the inhibitory effects of hunger motivation excitement on slow electrical muscle activity in the lesser curvature, body, and antrum of the stomach of satiated rabbits. Changes in slow electrical activity of the stomach muscles in rabbits deprived of food over 24 h and offered food and associated food-procuring behavior during electrical stimulation of the lateral hypothalamus have a two-phase pattern. Despite food intake during phase I of electrical stimulation, the downstream inhibitory effect of hunger motivation excitement on myogenic pacemaker of the lesser curvature of stomach abolishes the stimulating effect of food reinforcement on slow electrical muscle activity in the lesser curvature, body, and antrum of the stomach. During phase II of electrical stimulation, the food reinforcement decreases inhibitory effect of hunger motivation excitement on myogenic pacemaker of the lesser curvature that paces maximal rhythm of slow electrical waves for muscles activity in the lesser curvature, body, and antrum of the stomach, which is reflected by unimodal distribution of slow electrical wave periods. Our results indicated that the structure of temporal organization of slow electrical activity of the stomach muscles reflects convergent interactions of food motivation and reinforcement excitations on the dorsal vagal complex neurons in medulla oblongata.

Characteristics of rabbit food-procuring behavior as an indicator of changes in the level of hunger motivation.

We proposed new method for measuring dynamic changes in hunger motivation in rabbits in the course of satisfaction of nutritional need by weight, time, and rate parameters of effective food-procuring behavior. Transformation of the amount of food eaten into the electric signals was performed using electronic weighing machine incorporated into hardware and software system. The most conclusive characteristic for decrease in hunger motivation in the course of first effective food-procuring act was the period of food-procuring cycles, which values increase significantly as animal satisfies its nutritional need, whereas amount of the food consumed for each food-procuring cycle remains constant. Integral characteristics of food-procuring behavior reflect higher level of food motivation in the course of first effective food-procuring act in comparison to the subsequent ones.

Reflection of induced and amplified food motivation in impulse activity of the masticatory muscles during electrostimulation of the "hunger center" in the lateral hypothalamus in rabbits.

We studied reflection of artificially induced and amplified food motivation in impulse activity of the masticatory muscles during electrostimulation of "hunger center" of the lateral hypothalamus in the absence and presence of food. The threshold stimulation of the lateral hypothalamus in hungry and satiated animals in the absence of food induced incessant food-procuring behavior paralleled by regular generation of spike bursts in masticatory muscles with biomodal distributions of intervals between pulses. This reaction of masticatory muscles during stimulation of the lateral hypothalamus in the absence of food was an example of the anticipatory reaction reflecting characteristics of the action result acceptor. Higher level of hunger motivation during threshold stimulation of the lateral hypothalamus in hungry and satiated rabbits in the course of effective food-procuring behavior increased the incidence of spike burst generation during the food capture phase, but did not modify this parameter during the chewing phase. Impulse activity of the masticatory muscles reflected convergent interactions of food motivation and support excitation on neurons of the central generator of chewing pattern.

Reflections of hunger and satiation in the structure of temporal organization of slow electrical and spike activities of fundal and antral stomach muscles in rabbits.

Manifestations of hunger and satiation in myoelectric activity patterns in different portions of the stomach were studied in chronic experiments. The state of hunger manifested in the structure of temporal organization of slow electric activity of muscles in the stomach body and antrum in the form of bimodal distributions of slow electric wave periods, while satiation as unimodal distribution. In hunger-specific bimodal distribution of slow electric wave periods generated by muscles of the stomach body and antrum, the position of the first maximum carries the information about oncoming food reinforcement, since this particular range of slow wave fluctuations determines temporal parameters of slow electric activity of muscles in all stomach regions in the course of subsequent successive food-procuring behavior. Under conditions of hunger, the pacemaker features of muscles in the lesser curvature are realized incompletely. Complete realization is achieved in the course of food intake and at the state of satiation.

[Reflection of state of hunger and its changes under the influence of meals in time structure of myoelectrical activity of esophageal-gastric sphincter and gastric in rabbits].

OBJECTIVE: To study the reflection of the state of hunger and its changes under the influence of food intake in temporal structure of myoelectrical activity of gastro-esophageal sphincter and stomach in rabbits. MATERIAL AND METHODS: The registration of myoelectrical activity of gastro-esophageal sphincter and the stomach was performed in 10 rabbits subjected to daily food deprivation, before and after providing them powers ac DA-100 C and EMG-100 C (USA). Automatic analysis of temporal parameters of myoelectrical activity was monitored by the program AcqKnowledge (USA). Statistical analysis of the temporal parameters was performed using the program Statistica 6. RESULTS: The condition of hunger is characterized by irregular periods of slow waves generated by the muscles of gastro-esophageal sphincter, the body and antrum, which is reflected in the structure of their temporal organization in the form of bimodal distribution of periods of slow waves. Under the conditions of food deprivation regular generation of slow waves with a frequency of 3.6 cycles/ min is observed only in the lesser curvature--stomach pacemaker zone, as evidenced by the monomodal character distribution of periods of slow waves. However, the ability of muscles of the lesser curvature to define the maximum frequency of generation of slow waves to other parts of the stomach under the conditions of hunger is not fully realized. Food intake reinforcement reduces the inhibitory effect of hunger motivational excitation on the activities of myogenic pacemaker of the stomach, allowing the muscles of the lesser curvature to define a maximal rhythm of generation of slow waves to the muscles of the body and antrum, as evidenced by the monomodal distribution of periods of slow waves. In a state of satiation the maximum frequency of generation of slow waves of myogenic pacemaker of the lesser curvature is acquired by muscles of gastro-esophageal sphincter. CONCLUSION: The state of hunger and its change under the influence of food intake finds reflection in the specific structure of the temporal organization of the slow electrical activity of muscles of gastroesophageal sphincter and the stomach.

[Effect of electrostimulation "hunger center" of lateral hypothalamus on the impulse activity of masticatory muscles in unfed and fed rabbits in the absence and the presence of food].

In chronic experiences on rabbits the influence of electrostimulation of "the hunger centres" of the lateral hypothalamus (LH) on impulse activity of chewing muscles of rabbits under the conditions of hunger and satiation was studied. It is established, threshold irritation of the LH of hungry and preliminary fed animals in the absence of food caused the occurrence of incessant search behavior which was followed by the regular generation of bursts of AP by masseter and mylohyoideus muscles with bimodal distributions of interpulse intervals. Such reaction of chewing muscles during irritation of the LH in the absence of food is an example of advancing type reaction. The increase of level of alimentary motivation, arising at threshold irritation of the LH of rabbits under the conditions of hunger and satiety during the resultant food-intake behavior, increased frequency of generation of bursts of AP in a phase of the capture of food, but did not influence on this indicator in a phase of chewing of food. The received results testify about descending stimulating influences of alimentary motivational excitation on neurons of the chewing centre in medulla and on impulse activity of chewing muscles.

Effects of electrical stimulation of the hunger center in the lateral hypothalamus and food reinforcement on impulse activity of the mylohyoid muscle in rabbits under conditions of hunger and satiety.

Effects of electrical stimulation of the hunger center in the lateral hypothalamus and food reinforcement on impulse activity of mylohyoid muscle were studied in chronic experiments under conditions of hunger and satiety. Threshold stimulation of the lateral hypothalamus in starving and satiated rabbits in the absence of food induced searching behavior associated with burst-like impulse activity with a bimodal distribution of interpulse intervals. Regular spike burst in the mylohyoid muscle during stimulation of the lateral hypothalamus in the absence of food serves as an example of the anticipatory type reaction. Increased food motivation during threshold stimulation of the lateral hypothalamus in starving and satiated rabbits with food offered led to successful food-procuring behavior, during which the frequency of spike bursts in the mylohyoid muscle became comparable with that under conditions of natural foraging behavior stimulated by the need in nutrients. Our results suggest that temporal structure of mylohyoid muscle impulse activity reflects convergent interactions of food-motivation excitation with reinforcement excitation on neurons of the masticatory and deglutitive centers.

Method of evaluation of dynamic changes in food motivation in rabbits during successful food-procuring behavior.

We developed a method for evaluation of dynamic changes in the level of food motivation in rabbits during successful food-procuring behavior. Quantitative and temporal parameters of food consumption over each successive cycle of food-procuring behavior were used. The amount of consumed food was converted into electrical signal using an electronic balance incorporated into a hardware-software complex. Temporal parameters of food-procuring activity were determined by changes in electric signal in real-time mode. This method makes it possible to record simultaneously food-procuring activity and impulse activity of masticator muscles and esophageal muscles, which enables parallel analysis of rhythms of food consumption, mastication, and swallowing.

Effects of electrical stimulation of the hunger center in the lateral hypothalamus and food reinforcement on impulse activity of the proper masticatory muscle in rabbits under conditions of hunger and satiation.

Threshold stimulation of the lateral hypothalamus in starving and preliminary fed (satiated) rabbits in the absence of feed induces searching behavior associated with burst-like impulse activity of proper masticatory muscle with a bimodal distribution of interpulse intervals, what represents an anticipatory type of reaction. The increase in the level of food motivation during threshold stimulation of the lateral hypothalamus in starving and satiated rabbits with the food offered led to successful food-procuring behavior, during which the frequency and amplitude of spike bursts in the proper masticatory muscle become comparable with those under conditions of natural foraging behavior stimulated by the need in nutrients. Motivational excitation and backward afferentation from food reward are addressed to the same neurons of the masticatory center in the medulla oblongata.

[Electrophysiological analysis of bruxisma of rabbits as natural model of the first bruxism in human being].

In chronic experiences on 5 rabbits subjected to airmentary deprivation, impulse activity of the chewing muscles before and after the food was given to them was studied. It has been established, that flashes of bruxism nonoperiodically arise in rabbits in conditions of hunger and satiation and are shown in electric activity of masseter and mylohyoideus muscles in the form of burst type phase impulse activity of MU. Bruxism in conditions of hunger and satiation reflects in the same type way in structure of the time organization of impulse activity of the chewing muscles in the form of bimodal distributions of interpulse intervals and monomodal distributions of periods of the burst type rhythmic of action potentials. The alimentary motivation exerts inhibitory modulating influence on frequency of phase discharge activity of chewing center motoneurons in medulla oblongata and frequency of generation of the action potentials' bursts by the chewing muscles participating in bruxism. Impulse activity of chewing muscles during bruxism and food intake behaviour has the same-type character. Bruxism arises due to reorganization of the impulse activity of chewing center motoneurons innervating masseter and mylohyoideus muscles. There is no basis to suppose the presence of the special center of bruxism in medulla oblongata.Bruxism in rabbits an be considered as natural model of the first type bruxism in man.

Hunger and satiation in the structure of temporal organization of impulse activity of masticatory muscles in rabbits.

Impulse activity of masticatory muscles, jaw elevators and depressors, during hunger, eating, and satiation was studied in chronic experiments on rabbits. The state of hunger is specifically reflected in the structure of temporal organization of impulse activity of proper masticatory muscles as a monomodal distribution of interpulse intervals and in activity of the mylohyoid muscle as bimodal distributions. Food intake induces reorganization of the temporal structure of impulse activity in both muscles manifesting in the form of similar bimodal patterns of distributions of interpulse intervals.

[Impulse activity of masticatory elevator and depressor muscles of the lower jaw in rabbits in conditions of hunger, food intake, and satiety].

In chronic experiences on rabbits impulse activity of the chewing muscles elevating and depressing the lower jaw in conditions of hunger, food intake and satiation was studied. In conditions of alimentary deprivation of animals MU of masseter muscle nonperiodically show low amplitude regular impulse activity of tonic type, and MU of mylohyoideus -- burst type phase discharge activity that is reflected in the structure of the temporary organization of impulse activity of the masseter muscle in the form of monomodal distributions of interpulse intervals and mylohyoideus muscle -- in the form of distribution of bimodal type. Food intake causes reorganization of impulse activity of both muscles which represents in the form of bimodal patterns of distributions of interpulse intervals. The high degree of regularity of burst type rhythmic of action potentials of chewing muscles is the objective criterion of result food-intake behavior.

[Hypothalamic control of the myoelectric activity of the gastric antrum in rabbits during acute emotional stress].

During the experiments on the rabbits immobilized, which were undergone one day food deprivation, the influence of electric irritation of the lateral hypothalamus "hunger center" in condition of the acute emotional stress, that appears under unreinforcement of the artificially amplified hunger motivated excitation with food, which is located on the close but not reachable distance from animals, has been studied. It has been proved that increase of the alimentary motivation intensity in the process of the double-side turn-by-turn electric stimulation of digestive hypothalamic centers and appearance of uneffective food intake behaviour leads to rapid change of the bimodal patterns of the basic electric rhythm of the stomach distribution on the three-modal type distribution, which is typical for the state of hunger in condition of two days' food deprivation and also to the appearance of ectopic focus of excitations in the antral stomach part, and finally--to the development of ulcer-erosive injuries in the stomach mucosa.

[Functional organization of myogenic pacemaker of the stomach in conditions of hunger and satiation]. / Funktsional'naia organizatsiia miogennogo peismekera zheludka pri golode i nasyshchenii.

In chronic experiments, we have studied electrical activity of muscles of the gastro-esophageal sphincter, small curvature, corpus and antrum of the stomach in conditions of hunger, food intake behaviour and satiation of the rabbits. The aim of this study involved particularities of the electrical activity of myogenic pacemaker zone of the stomach. It has been shown that function of myogenic pacemaker of the rabbit stomach is performed by smooth muscles of the small curvature of the stomach. Pacemaker properties of muscles of the small curvature of the stomach are performed in conditions of food intake behaviour and satiation.

[The mechanism of inhibition of small intestine contractions following irritation of rabbit's vagus nerve]. / Mekhanizm tormozheniia sokrashchenii tonkoi kishki, voznikaiushchego pri razdrazhenii bluzhdaiushchego nerva u krolika.

Explored was mechanism of inhibition of small intestine contractions due to weak irritation (0.5-2.5 V, 1-30 Hz, 0.3-1.0 ms) of the peripheral segment of rabbit's right vagus nerve. It was shown that the inhibitory effect can be blocked by benzohexamethonium, arphonade, atropine, rhausedyl, and a combination of propranolol and dehydroergotoxine. Inhibition is triggered by catecholamines released by sympathetic endings in consequence of activation of presynaptic M-cholinoreceptors on their surface. Presynaptic M-cholinoreceptors are activated by acetylcholine released by the endings of postganglionary parasympathetic nerve fibers.