Molecular mechanisms underlying sensorimotor cortex pyramidal neuron involvement in the feeding behavior of rabbits

Response in pyramidal neurons belonging to the sensorimotor cortex (37% of total nerve cells investigated in this zone) which were identified by stimulating the bulbar pyramids, were investigated during experiments on unrestrained rabbits. Pyramidal neurons having connections with the lateral hypothalamus were activated during operation of feeding behavior, while activity was inhibited in those unconnected with the lateral hypothalamus. Microiontophoretic application of a protein synthesis inhibitor to pyramidal neurons caused their ability to respond to ascending activating influences from the lateral hypothalamus to disappear. When pentagastrin was applied to these neurons following the protein synthesis blocker, they recovered their ability to participate in hypothalamic feeding reaction. It is suggested that synthesis and release of a gastrin-like peptide into the perineuronal space is required for sensorimotor cortex pyramidal neurons to participate in the organization of feeding behavior.P. K. Anokhin Institute of Normal Physiology, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 19, No. 5, 601–606, September–October, 1987.     

Pentagastrin as a factor in the selective recruitment of dorsal hippocampal neurons in the organization of goal-directed feeding behavior

Single unit activity of the rabbit dorsal hippocamp in response to electric stimulation of the food centers of the lateral hypothalamus has been studied. Threshold stimulation produced food motivation and subthreshold one the orienting-research reactions. Microiontophoretic application to the neurons of the protein synthesis blocker cycloheximide induced changes in single unit activity in response to threshold stimulation in 79% of cases, whereas to subthreshold stimulation in 53% of cases. Application to these neurons of pentagastrin recovered the reactions only to threshold stimulation. It is inferred that the involvement of the majority of CA3 dorsal hippocampal neurons in food motivation requires the presence in the perineuronal space of a definite amount of pentagastrin that is likely to be synthesized, under normal conditions during motivational stimulation, in the given or adjacent neurons.     

Integrative properties of parietal cortex neurons of rabbits during the switching of heterogeneous classical conditioned reflexes

The impulsive activity of parietal cortex neurons of rabbits during the elaboration and specialisation of switching-over of alimentary and defensive conditioned reflexes has been studied. There are changes of parietal cortex neurons activity correlated with the stages of switching-over elaboration. The significant differences of the background neurons activity and neurons response to the conditional signal during alimentary and defensive conditioned reflexes have been established. The dominant motivation influences the neurons activity by modulation of background and conditioned activity of neurons. The integrative properties of neurons investigated in switching-over situation are revealed in their ability to summarize the excitation coming to the same sensory input with excitation from different motivational and reinforcement systems.     

The facilitation of defensive reactions during food consumption in the snail helix: the participation of glucose and gastrin/cholecystokinin-like peptide]

Molecular and cellular mechanisms of the interrelations between the feeding and defense behaviour were studied in a snail Helix lucorum. The dynamics of defense reactions was investigated in snails with different levels of feeding motivation. Defense reactions were suppressed in hungry snails, while 15-20 min after the beginning of food intake they were facilitated. The facilitation depended on a duration of starvation. Injection of 0.5 ml of 5 mM glucose solution (up to the glucose level in the haemolymph of a food satiated snail, 1.6-2.0 mM) or injections of 20-30 ng of synthetic analogues of the gastrointestinal peptides (pentagastrin of octapeptide cholecystokinin, CCK-8) facilitated the defense reaction in a hungry snail. Parameters of the facilitation were similar to those in the period of food intake. Activity of the command neurons of defense behaviour (L-PPL1) after the carrot juice application to the lip of a semi-intact preparation from a hungry snail was glucose-dependent. Similar glucose-dependent changes of L-PPL1 activity were found after CCK-8, but not FMRFamide application during the perfusion with 0.5 mM glucose. L-PPL1, but not L-PPa2-3 neurons were most sensitive to glucose and CCK-8 level changes in the Ringer solution. Adaptive significance of the behavioural phenomena as well as glucose and gastrin/CCK-like peptide participation in these processes are discussed.     

Activity of neurons in the pedunculopontine nucleus during defensive instrumental conditioning

The activity of 109 neurons in the compact and diffuse parts of the pedunculopontine tegmental nucleus (PPTg) was recorded in freely moving rabbits during the acquisition and actualization of the defensive instrumental conditioned reflex. It was found that 47% of the recorded neurons responded to a conditioned stimulus (CS). This finding suggests the involvement of the PPTg in the instrumental conditioning. A significant prevalence of the excitatory conditioned responses to the CS suggests the predominantly activating influence of the PPTg on its projection structures during conditioning. The neuronal responses to the CS were classified into several basic patterns reflecting stimulus effects, the structure of the behavioral act, and the nature of the reinforcement. They indicated the involvement of the PPTg in attention, motor learning, and reinforcement. A significant decrease in the reactivity of the CS of the PPTg neurons as a result of learning specialization was shown. The revealed differences in the associative and reactive properties (with respect to CS) between the neurons of the compact and diffuse PPTg parts testify to the functional heterogeneity of this structure and suggest the leading role of the cholinergic compact part of the PPTg in the instrumental defensive conditioning. Thus, the obtained evidence suggests the involvement of the PPTg in the mechanisms of attention and acquisition of the active defensive motor conditioning.     

Differences in activity of hippocampal and neocortical neurons in active and passive rabbits in negative emotional situations

Activities of individual hippocampal (CA1 area) and neocortical parietal-temporal neurons were compared in active and passive rabbits in negative emotional situations during emotionally significant stimuli by plotting histograms of autocorrelations. As compared to passive animals, in active rabbits, the mean firing rate of hippocampal neurons was higher, bursting and periodic oscillations of discharges occurred more frequently. Oscillation periods in the theta 1 band (6.0-9.0 Hz) appeared more frequently (in the baseline state and active exploratory or defensive reactions), whereas those in the theta 2 band (4.0-5.9 Nz), on the contrary, were infrequently observed (during freezing). The greatest changes in activity ofhippocampal neurons were observed during active locomotor responses of active rabbits. Intergroup differences in neocortical neuronal activities were less pronounced than in hippocampus. The results indicate that individual typological features in behaviour of animals appear in negative emotional situations and are reflected in activity of activity ofhippocampal (area CA1) and to lesser extent parietal-temporal neocortical neurons. The results suggest different activation levels of the septohippocampal system of active and passive rabbits and possible differences in the afferent input to the CA1 field.     

Participation of peptides in processes involved in the development of alimentary motivation in the rabbit

On the base of behavioural and electrophysiological experiments it was suggested that in rabbits the realization of the dominant feeding motivation into the goal-directed behaviour implied at the molecular-genetical level the operative synthesis of gastro-intestinal neuropeptide gastrin or its derivatives. It was supposed that the suppression of genetic information realization in CNS under blocking of peptide synthesis led to impossibility of goal-directed alimentary behaviour organization. This mechanism was found to be specific for alimentary behaviour; any its connection with defensive motivation realization was not observed.     

Neuropeptides in the mechanisms of the activation of escape reactions induced by stimulation of the ventromedial hypothalamus during food motivation satiation

Influence of food intake on hypothalamically induced avoidance reactions have been studied in rabbits. It was shown that first contact with food and beginning of food intake accompany with activation of avoidance reactions. Central action of cholecystokinin-octapeptide, pentagastrin, beta-endorphin and naloxone on avoidance reactions of fed and fasted rabbits before and during food intake was investigated. It was found that injection of cholecystokinin and naloxone, which had a satiated effect, act on avoidance reactions similarly in fed and fasted rabbits. Beta-endorphin inhibits avoidance behavior, and only pentagastrin activates avoidance reactions of fasted but not fed rabbits. It is concerned that influence of feeding motivation may modulate avoidance behavior by participation of endogenous gastrin-like peptide release into the perineuronal area during contact of rabbits with food and beginning of its intake.     

Participation of hippocampal neurons on the stages of feeding behavior

Activity of 65 hippocampal single units was recorded during an instrumental feeding behaviour in three rabbits. Different neurons fire or change their spontaneous activity in one or more behavioural acts, which constitute the consecutive behaviour. In one or the other behavioural act single unit discharges occur both after and before some intermediate results. Participation of hippocampus in organization of the consecutive behaviour is discussed.     

The effect of acute alcohol administration on auditory evoked potentials in altricial nestlings during the development of natural behavior]

Acute ethanol influence on field L auditory evoked potentials (AEP) was studied in 4-8-days-old altricial nestlings of pied flycatcher. Nestlings were presented with tone pips related with the realization of natural behaviour (2.0 and 5.0 kHz) and bearing no meaning for the behaviour of the young of the age under study (3.0 kHz). Ethanol ingestion was found to reduce the maturity index (MI) of AEP in response to "behavioural" but not to control frequencies; this effect was first observed at day 5, when nestlings eyes opened and defence behaviour appeared, while previously formed feeding behaviour was significantly modified. During the next 2 days alcohol had a greater effect upon the AEP in response to 2.0 kHz tone pips, related with feeding behaviour of increasing complexity than upon the AEP in response to 5.0 kHz, related with the defence behaviour that remained relatively constant. The previous data concerning the effect of alcohol on unit activity are used to support the view that MI increase during the early postembryonic ontogeny is due to the involvement of neurons with newly formed behavioural specializations into the subserving of new behavioural patterns while the decrease of MI under alcohol is due to the depression of activity in these neurons.     

The participation of GFAD-synthesizing neurons in behavior regulation in the snail (Helix lucorum L.)

It was shown earlier that some neurons in Helix CNS express the mRNA of the precursor of neuropeptide GFAD. Using the data obtained with the help of the whole-mount in situ hybridization, we tried to identify a group of such neurons, namely, the pedal caudo-ventral group and to determine their possible functions. The local extracellular stimulation of the pedal caudo-ventral group resulted in movements of reproductive organs in the semi-intact preparation and suppressed the activity of the modulatory neurons controlling feeding and defensive behavior. Application of synthetic peptide GFAD (10(-8) mol/l) also activated movements of the reproductive organs and suppressed the activity of the modulatory neuron controlling feeding behavior. Stimulation of the labial nerves resulted in suppression of caudo-ventral neurons with simultaneous activation of the modulatory neuron controlling feeding behavior. The obtained evidence suggests that the caudo-ventral neurons can regulate movements of the reproductive organs and also coordinate different functions in realization of the integral sexual behavior. This group of neurons inhibits the modulatory neurons controlling the forms of behavior incompatible with courtship, i.e., feeding and defensive forms.     

Dynamics of driven rhythm in neuronal assemblies in sensorimotor and visual cerebral cortices in rabbit

Coincident activity of pairs of neurons in the sensorimotor and visual areas of the cerebral cortex was studied in naive, learning, and trained rabbits during the formation of a hidden excitation focus in their central nervous system (a defensive dominanta) of the rhythmic nature. In the trained rabbits (as compared to the naive animals), percent of neuronal pairs (both neighboring and distant) in whose coincident activity the rhythm of stimulation prevailed was higher. In the visual cortex, percent of such pairs was significantly higher only for the distant neurons. Analysis of interaction between neurons in the visual and sensorimotor cortices revealed increasing the number of neuronal pairs with the driven rhythm while training. Such an increase was observed when both sensorimotor and visual neurons were considered as leading.     

Effects of host grooming on louse populations

Grooming behaviour by the host is increasingly recognized as an important determinant of feeding behaviour by blood-sucking arthropods. In general, grooming activity increases as a function of attack rate which, in some cases, provides a density-dependent limitation on the success of blood feeding. In turn this can lead to density dependence in population parameters of the arthropod, and can affect transmission of some arthropod-borne parasites in a similar way. But although insect-host interactions at this level are now being revealed in a variety of blood-sucking groups, such as mosquitoes, tsetse flies and triatomine bugs (see Box I), they are perhaps most clearly seen in, populations of ectoporositic insects such as lice, which ore permanently subject to defensive grooming behaviour by their hosts. As Durno Murray discusses here, host grooming has been a dominant factor in the evolution of lice, not only at the morphological level but also in terms of reproductive strategy.     

Effect of ethanol on central mechanisms of alimentary and defensive motivation in the rabbit

A single intravenous administration of ethanol (0.5 g/kg) to rabbits had different effects on the excitability of feeding and defensive motivational centers of the lateral and ventromedial hypothalamus. Ethanol abolished both inhibitory effects of the dorsal hippocampus and facilitatory action of the midbrain reticular formation on alimentary and defensive motivations. It elicited new power distributions of the main rhythms of general electrical cortical activity in the background and under stimulation of limbic-midbrain structures. Analysis of the activity of organello-specific enzymes in limbic-midbrain neurones revealed disturbances of cellular energetic processes caused by ethanol.     

Electrophysiological study of effects of chronic injection of caffeine on defensive reflex conditioning in grape snail

It was found that chronic injection of caffeine to grape snail increases a velocity of elaboration of conditioned defensive reflex. It was shown that after daily injection of caffeine immediately after procedure of learning the conditioned defensive reflex elaborated faster than daily injection before procedure of learning. It has been shown, that chronic injection of caffeine both in naive as well as learned snails led to depolarizing shift of membrane potential and to decrease of threshold potential of command neurons of the defensive behaviour of grape snails. It was also found that addition of caffeine in bath solution led to decrease of threshold of generation of action potential of command neurons both in intact and learned snails. The resting membrane potential of command neurons was not changed.     

The effect of adrenoblockers on the neurons of the lateral hypothalamus under the action of pentagastrin]

To test the hypothesis of interaction pentagastrin (PG) noradrenaline (NA) in central neurochemical mechanisms of food motivation, we studied the activity of single neurons in lateral hypothalamus (LH) after s.c. PG injection. Following PG injection microiontophoresis (MIF) of propranolol prazosin was made. PG-induced changes were similar to neuronal activity in rabbits LH after 24-hour food deprivation in 59%. Propranolol-induced changes were following firing pattern in the process of food uptake in 68%. Prazosin MIF induced firing pattern of neuronal activity of saturated rabbits in 60%.     

Effect of environmental information richness during early development of bream (<Emphasis Type="Italic">Abramis brama</Emphasis>; Cyprinidae) upon feeding and defensive behavior of its yearlings

The feeding behavior of bream (Abramis brama) yearlings kept before the experiment (four months post hatch) under different conditions has been studied. Three variants of conditions, varied in their levels of informational richness, were modeled for keeping young fish prior to the experiments: 1—minimal richness, mimicking conditions of standard commercial hatchery containers; 2—the conditions enriched by a water current; 3—the conditions enriched by modeled impact of predation and feeding by live food. In the following experiments, the conditions were similar for all three groups. It was revealed that the fish grown under the conditions of Variant 1 had a lower learning ability, higher extent of schooling behavior, and lower efficiencies of feeding and defensive behaviors. Similar traits were described in literature as being typical for the fish grown at standard fish farms. The Variant 2 fish had the shortest adaptation period and most efficient feeding behavior but were lacking the skills of defensive behavior. The fish from the 3rd variant had a medium duration of adaptation period and efficient feeding behavior and possessed well-developed skills of defensive behavior. The results have shown that the level of environmental information richness during fish early life stages plays a crucial role in further development of the most important adaptive forms of behavior. Maintaining the young fish in containers with water current facilitates swimming performance and development of feeding behavior. However, such fish, in fact, lack the skills of defensive behavior.     

Gastrin in the mechanisms of genetic determination of feeding behavior in rabbits

Spreading of a dominant motivation to the molecular intracellular mechanisms of genetic memory was studied. Blockage of protein synthesis in the nervous system selectively abolishes food motivation in rabbits during stimulation of the lateral hypothalamus but exerts no noticeable effect on avoidance responses during stimulation of the ventromedial hypothalamus. During protein synthesis blockage, food motivation returns to normal upon pentagastrin intracerebroventricular (i.c.v.) injection. Intracerebroventricular administration of antigastrin immunoglobulin inhibits feeding reaction to lateral hypothalamic stimulation but not avoidance response to ventromedial hypothalamic stimulation. It was concluded that feeding motivation translates into feeding behavior in the following stages: motivational excitation, gene activation, mRNA synthesis, formation of a gastrin-like peptide, and expression of feeding behavior.     

Underwater observations of piranhas in western Brazil

Synopsis The behaviour of three piranha species,Serrasalmus marginatus, S. spilopleura, andPygocentrus nattereri, and their prey fishes was studied underwater in the Pantanal region, Mato Grosso, Brazil. General habits, predatory tactics, feeding behaviour, and social interactions while foraging, as well as defensive tactics of prey fishes were observed.S. marginatus is solitary whereas the other two species live in shoals; their agonistic behaviour varies accordingly, the simplest being displayed by the solitary species. Predatory tactics and feeding behaviour also vary:S. spilopleura shows the most varied diet and highly opportunistic feeding strategy, which includes aggressive mimicry. The solitaryS. marginatus, besides fin and scale-eating, occasionally cleans larger individuals ofP. nattereri. Several cichlid species display defensive tactics clearly related to piranha attacks: tail protecting, watching, and confronting the predator are the most commonly observed behaviours. Piranhas seem to strongly influence use of habitat, social structure, and foraging mode of the fish communities.     

Oligopeptides in the development of biological motivations

Data are presented, demonstrating the action of a number of oligopeptides on biological motivations of hunger, fear, self-stimulation and on alcohol addiction. In the structure of animals feeding motivation, such oligopeptides take part as beta-lipotropin and its fragments, ACTH, pentagastrin, delta-sleep inducing peptide (DSIP), substance P; in organization of defensive motivation--angiotensin II (AII), DSIP, substance P, bradykinin, beta-endorphin etc.; in organization of self-stimulation--AII, DSIP, bradykinin, ACTH, beta-endorphin etc. It is established that most of the above oligopeptides, injected to the brain lateral ventriculi, inhibit biological motivations, and only some of them have an activating action. On the basis of experiments, a hypothesis is formulated that oligopeptides act as a feedback between the genome of brain neurones and pacemaker cells of motivation centres of the hypothalamus area. Some oligopeptides elaborated by neuronal genomes under the action of dominating motivation, activate--and the other--suppress the activity of motivation hypothalamus centres.