The reinforcing action of stimulation of the mesocerebral area of the brain in the edible snail]

Reinforcing effect of extracellular stimulation of two brain zones on spontaneous opening of pneumostome was investigated in semi-intact preparation of the snail. It was found that mesocerebrum stimulation increased the frequency of the reinforced movement, but decreased the frequency of the same movement it its absence was reinforced. These results suggest positive reinforcing effect for this brain area involved in control of sexual behaviour. Different results were obtained for stimulation of rostral part of parietal ganglia where giant cells controlling avoidance behaviour are located. Stimulation of this area decreased the frequency of the ongoing spontaneous movements. Implications for the control of behaviour are considered.     

Brain cells that command sexual behavior in the snail Helix aspersa

Evidence is presented indicating that the mesocerebrum of the terrestrial snail, Helix aspersa, has a major role in the control of sexual behavior. Morphological and physiological results demonstrate a right-sided bias in the mesocerebrum that is consistent with the fact that sexual behavior is executed almost entirely on the animal's right side. Thus, the right lobe has 23% more neurons than the left lobe, and they are 24% larger. Excitatory synaptic inputs derive predominately from neurons on the right side. The axons of right-side mesocerebral neurons go to the right pedal ganglion almost without exception, and even the axons of left-side neurons travel mostly in right-side connective nerves. Direct evidence for a role of the mesocerebrum in commanding sexual behavior comes from experiments with electrical stimulation. Extracellular stimulation of the right mesocerebrum, but not the left mesocerebrum, resulted in movements of the "love dart" sac and the penis. Intracellular stimulation of neurons in the right mesocerebrum evoked measurable movements of either the dart sac or the penis, or both, in 17% of the cells tested. The latencies ranged between 5 and 50 s. In an intact animal, these movements would cause a release of the dart and an eversion of the penis. The motor effects were mediated through the right cerebropedal connective and the pedal nerve NCPD, with the motorneurons probably situated in the right pedal ganglion.     

Double labelling of neural grafts for identification of sites mediating growth in snails

Several parameters were studied in an experiment on intracerebral neural grafts in young snails (Helix aspersa aspersa) in which growth was blocked by removal of the mesocerebrum. The results demonstrate that transplantation of adult mesocerebrum neurons from another subspecies (H aspersa maxima) into the location of the ablated mesocerebrum in the brain of a young juvenile host, leads to functional recovery. In addition, double labelling with charcoal for topographical localisation and fast blue for observation of survival and integration of fluorescent cells within the host brain demonstrated the tolerance to the grafted cells and the successful growth of the chimeric brain. The surviving neurons were mainly located in the median region of the reconstituted brain near the islets of metacerebrum neurons. It is possible that some trophic factors promote growth in the host brain and development of the grafted cells. However, resumption of growth requires the presence of the neurosecretory cells particular to the mesocerebrum which secrete growth hormone. The fast-blue dye, which is still detectable after several months, is useful to track single cells for the study of the functional capacities of the different populations of neurons in the cerebral ganglia and for exploring neuronal replacement strategies in the damaged brain.     

Crossed and uncrossed afferent inputs of mesocerebral neurons of the mollusk Planorbis corneus

Experiments on the isolated ganglionic ring of the freshwater molluskPlanorbis corneus showed that more neurons (30%) in the ipsilateral mesocerebrum respond to stimulation of the left cerebral nerves than to stimulation of the opposite nerves (13%). A similar picture is observed for neurons of the right mesocerebrum, except that 11% of neurons respond to activation of the left cerebral nerves compared with 39% to stimulation of the ipsilateral right cerebral nerves. Ipsilateral connections of nerve of the visceral complex of ganglia are more clearly defined, as is exemplified by the left pallial nerve, during stimulation of which 68% of neurons in the ipsilateral mesocerebrum were activated, compared with 8% in the contralateral right mesocerebrum. Afferent fibers running in the visceral nerves cross at the level of the abdominal ganglion and not of the cerebral commissure, as might be expected from the structure of the ganglionic ring. The mesocerebral neurons themselves do not form synaptic connections between the mesocerebra, and excitation reaching one of them does not therefore induce any effects in the other.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 5, No. 6, pp. 571–575, November–December, 1973.     

Electroencephalographic studies on classically conditioned defensive reflex and avoidance lever-pressing in the dog (author's transl)]

Six dogs with implanted cortical and subcortical electrodes were trained to press a lever to avoid electroshock to a hind leg. Intracerebral stimulation at low frequency was delivered as an "indifferent" or a "CD" tracer. Changes of EEG responses to the tracers prior to the voluntary lever-pressing or the conditioned avoidance lever-pressing were prior to the voluntary lever-pressing or the conditioned avoidance lever-pressing were examined by continuous frequency analysis. (1) Evoked potentials to the tracer stimulation were changed just before the conditioned defensive reflex, the voluntary lever-pressing and the conditioned avoidance lever-pressing, regardless of the site of the tracer stimulation. (2) The cortical and subcortical structures (Hippo, RF) seemed to be involved in the neural circuit responsible for the avoidance lever-pressing, whereas the sensorimotor cortex may be essential in the circuit for the alimentary lever-pressing. (3) The avoidance lever-pressing and the EEG response to the "CS" tracer were influenced by the internal inhibition (experimental extinction, inhibitory mechanism was discussed.     

Analysis of the participation of rat brain noradrenergic terminals in elaboration of conditioned passive avoidance response]

A change in a noradrenaline concentration in the noradrenergic terminals was investigated by the fluorescent histochemical method in pars ventralis nuc. interstitialis striae terminalis, nuc. septi lateralis and in nuc. preopticus medialis of male Wistar rats in the process of reproduction of conditioned passive avoidance response. In all the investigated structures of the preliminarily trained animals the reproduction of a conditioned response (without any electrical stimulation) led to a statistically reliable decrease in the noradrenaline concentration. The data obtained testified to the participation of the noradrenergic brain system in the reproductive process of the conditioned passive avoidance response.     

Gastrin-cholecystokinin immunoreactivity in the central nervous system of Helix aspersa during rest and activity

The immunostaining pattern for the peptide gastrin/cholecystokinin 8 (gastrin/CCK8) in the molluscan central nervous system has been considered. The changes in the distribution of gastrin/CCK8 immunoreactivity were analyzed in the neurons of different areas of the cerebral ganglia (mesocerebrum and metacerebrum) and in the buccal ganglia of the terrestrial snail Helix aspersa, during rest and active phases. During the period of inactivity and after one day of activity, there were several immunoreactive neurons in the mesocerebrum and metacerebrum of the snails and in the buccal ganglia, whereas after 7 days of activity the number of labeled neurons decreased. Data suggested a storage of gastrin/CCK8 in the neurons when behavioral activities in which the peptide is involved (such as feeding-related behavior) are suppressed or reduced. The different percentage of gastrin/CCK8 immunoreactive neurons in the left and right mesocerebrum provides information about the activities controlled by these neurons, which could be related to the adaptive evolution and plasticity of the brain in terrestrial pulmonates.     

Mechanically induced avoidance response of chloroplasts in fern protonemal cells.

Cell response to mechanical stimulation was investigated at a subcellular level in protonemal cells of the fern Adiantum capillus-veneris L. by pressing a small part of the cell with a microcapillary. In cells receiving local stimulation, the chloroplasts moved away from the site of stimulation, whereas the nuclei failed to show such avoidance movement. Mechanical stimulation for a period as short as 0.3 min was enough to induce the avoidance response to a maximal level. The avoidance movement of chloroplasts started within 30 min and the plateau level of avoidance was attained around 2 h after stimulation. By tracing the movement of chloroplasts during the response, it was shown that the mobility of chloroplasts near the stimulation site increased transiently within 1 h after the stimulation. After 2 to 3 h, it slowed down to the control level without stimulation. The avoidance response was inhibited by 0.1 mM cytochalasin B and 25 mM 2, 3-butanedione monoxime but not by 3.3 microM amiprophosmethyl or 5 mM colchicine. These findings indicate that the protonemal cells were very sensitive to mechanical stimulation and that chloroplasts moved away from the mechanically stimulated site through the actomyosin motile system.     

Analysis of the memory trace nature in passive avoidance response

Passive avoidance conditioning is analyzed in a three compartment apparatus that consists of a light compartment, a dark dangerous compartment in which foot shock was delivered, and a dark safe one where the rats were not shocked. It is concluded that latency increase of passive response is caused not by memory of the shock in a strictly certain location and, accordingly, not by shock avoidance in it, but by non-specific defensive response (freezing) unrelated to the shock location.     

Effect of stimulus parameters in the treatment of seizures by electrical stimulation in the kainate animal model

Preliminary results from animal and clinical studies demonstrate that electrical stimulation of brain structures can reduce seizure frequency in patients with refractory epilepsy. Since most researchers derive stimulation parameters by trial and error, it is unclear what stimulation frequency, amplitude and duration constitutes a set of optimal stimulation parameters for aborting seizure activity in a given patient. In this investigation, we begin to quantify the independent effects of stimulation parameters on electrographic seizures, such that they could be used to develop an efficient closed-loop prosthesis that intervenes before the clinical onset of a seizure and seizure generalization. Biphasic stimulation is manually delivered to the hippocampus in response to a visually detected electrographic seizure. Such focal, responsive stimulation allows for anti-seizure treatment delivery with improved temporal and spatial specificity over conventional open-loop stimulation paradigms, with the possibility of avoiding tissue damage stemming from excessive exposure to electrical stimulation. We retrospectively examine the effects of stimulation frequency (low, medium and high), pulse-width (low and high) and amplitude (low and high) in seizures recorded from 23 kainic acid treated rats. We also consider the effects of total charge delivered and the rate of charge delivery, and identify stimulation parameter sets that induce after-discharges or more seizures. Among the stimulation parameters evaluated, we note 2 major findings. First, stimulation frequency is a key parameter for inhibiting seizure activity; the anti-seizure effect cannot be attributed to only the charge delivered per phase. Second, an after-discharge curve shows that as the frequency and pulse-width of stimulation increases, smaller pulse amplitudes are capable of eliciting an after-discharge. It is expected that stimulation parameter optimization will lead to devices with enhanced treatment efficacies and reduced side-effect profiles, especially when used in conjunction with seizure prediction or detection algorithms in a closed-loop control application.     

Photic Inhibition of Brain Stimulated Firefly Flashes

A study of the effects of photic stimulation on the abilityto induce flash luminescence in the female Photuris fireflyby electrical brain stimulation was made. Pulses of light deliveredto the eye of the firefly aie not only able to inhibit spontaneousflashing but also reduce the ability of electrical biain stimulito induce firefly flashes. Inhibition by photic pulses is mosteffective when the pulses are delivered approximately 300–400msec prior to brain stimulation. Only flashes of biain stimulus—flashonset latency greater than 120 msec can be inhibited in thisfashion, while driven flashes of 90 msec were immune from theinhibitory effect. It is suggested that the inhibilory effectsof photic stimulation provide some physiological explaintionof the male-female response latency found in the courting fireflies.     

Tolerance to the anti-avoidance properties of cholecystokinin-octapeptide

Previous investigations have suggested a neuroleptic-like action of cholecystokinin-octapeptide (CCK8) on conditioned-avoidance behavior. This study was initiated to test tolerance to this effect. Rats were trained to avoid electric shock in a shuttle box under a free-operant (Sidman) avoidance paradigm. Each shuttle response postponed a 0.2 sec, 1 mA shock for 20 sec. If the rat failed to respond, shock was delivered every 5 sec until a response occurred. After avoidance training, half of the rats received two daily injections of CCK8 (0.320 mg/kg, IP) and half received saline for 7 days. Rats were then tested on the Sidman avoidance 1 min after receiving CCK8 (0.640 mg/kg, IP) or saline. CCK8 depressed avoidance responding if rats received saline for 7 days prior to the test. Rats pretreated with CCK8 for 7 days were not significantly affected by CCK8 during the avoidance test. Thus, repeated injections of CCK8 result in tolerance to its anti-avoidance properties.     

Effects of frontal brain electroshock stimulation on eeg activity and memory in rats: Relationship to ECS-produced retrograde amnesia

Electroencephalographic changes occurring in rat brain following frontal cortex stimulation in non-lesioned rats and in rats with bilateral lesions in the region of amygdala were investigated in Experiment I. Seizure duration and EEG spike frequency varied systematically with current level. The amnesic effects of conventional ECS and frontal cortex stimulation were studied in Experiment II. Both treatments were highly effective in producing retrograde amnesia for an inhibitory avoidance response. The findings are interpreted as suggesting that the effectiveness of ECS in producing RA varies with the amount of current reaching the brain.     

Integration of the effects of a single stimulus applied to the vagus nerve on the right and the left, in the rabbit heart

It was reported by the literature that a train stimulation, simultaneously delivered on the two vagi, resulted in a decrement of the negative chronotropic effect, when it was compared to the sum of the effects obtained by the stimulation of the two nerves, separately. Our data indicate that the size of the chronotropic effect obtained by the simultaneous application on the two vagi of a single supraliminar stimulus, randomly applied within the P-P cycle, in rabbits, can be equal, higher or lower than the sum of the same stimulation separately delivered to the two nerves. The results could depend upon the different amount of acetylcholine released during stimulation. The hypothesis is put forward that different patterns of the neuro-cardiac junction regulation might be activated according to the quantity of released neuromediator.     

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.     

Relation between the dynamics of a species-specific motor reaction and the duration of diencephalic stimulation

Species-specific reaction of thumping behaviour with the hind limbs in response to electrical stimulation of the ventromedial, dorsomedial and caudal parts of the hypothalamus was studied in chronic experiments on rabbits. Reaction of avoidance dominated during current action of various durations (1-20 s). The specific reaction under study appeared after the termination of stimulation and lasted for 30-120 s. The number of kicks in response to single stimulation depended on its duration (T). With T rising from 1 to 10 s, the number of kicks increased; with T being equal to 20 s, it decreased. The latency of the first kick after the termination of stimulation regularily increased with increase of its duration, and reaction intensity maxima shifted to the right along the axis of time. Possible mechanisms of limb kicking behaviour are discussed based on a transition of avoidance reaction during stimulus action to emotional reaction in post-stimulus period.     

Postsynaptic mechanism of withdrawal reflex sensitization in the snail

Repeated tactile stimulation of the skin evoked sensitization and subsequent habituation of a behavioral avoidance reaction of pneumostome closure in the land snail, Helix lucorum L. Spike responses in putative command neurons for avoidance behavior increased and subsequently decreased parallel to behavioral events. Decrease of spike responses in command neurons was due to decreased synaptic input evoked by repeated tactile stimulation. Intracellular investigation of the increase in the spike response in command neurons for pneumostome closure, which underlies behavioral sensitization, revealed a synpatically-evoked, long-lasting depolarization. No conductance changes during this depolarization were found, but neuronal excitability was altered.     

Role of angiotensin II in elaborating the escape reaction during electric stimulation of the ventromedial hypothalamus in rabbits

The action of angiotensin-II, saralazin, captopril and antiserum to angiotensin-II, injected into the brain ventricles, on avoidance reaction to electrical stimulation of ventromedial hypothalamus was studied in experiments on rabbits. It has been found that angiotensin-II had a pronounced inhibitory effect, while saralazin, captopril and antiserum to angiotensin-II had a facilitating effect on the reaction.     

Behavioral reactions to stimulation of the emotiogenic zones of the brain in the rats with different individual experience

Emotional reactions evoked by electric stimulation of the hypothalamus and amygdala were studied in white outbred rats, grown either in conditions of isolation or in community. The method of self-stimulation in shuttle box was used. The values of self-stimulation reaction were significantly lower and those of avoidance reactions were higher in animals bred in isolation. Their food-procuring behaviour disappeared faster at stimulation of the negative emotiogenic zones. The observed differences are due to plastic reorganization of the brain reinforcing systems.     

Modulation of the immune response by emotional stress

The influence of mild, emotional stress was investigated for its effect on the immune system by subjecting rats to the one-trial-learning passive avoidance test. The reactivity of the immune system was tested by determining the proliferative response after mitogenic stimulation in vitro as well as the capacity to generate a primary antibody response in vivo after immunization with sheep red blood cells. Our results demonstrate that exposure of rats to a single electric footshock (learning trial) or habituation to the passive avoidance apparatus, induces an increase of the immune response in vitro and in vivo. Thus, emotional stimuli seem to facilitate immunological responsiveness. However, when the animal is confronted with a conflict situation, as tested by the retention of the avoidance response after a single learning trial, the initially enhanced reactivity of the immune system decreases. It is concluded that the immune system is capable of reacting specifically and immediately to distinct psychological stimuli.