Effect of a dominant focus created in the center of the wink reflex on the local defense reflex in the rabbit

The paper deals with conjugated inhibition of rabbit's defensive limb reflex at formation of a dominant focus in the center of the eye-lid reflex. In the initial period of dominant focus formation, when the dominant comes through the stage of summation reflex, electrocutaneous limb stimulation induced, along with successive summation, temporary inhibition of the forming dominant focus. The dominant focus formed in the eye-lid center did not induce conjugated inhibition of the limb defensive reflex. In the study of the influence of the eye-lid reflex on the motor defensive one it was found that formation of temporary connection of summation reflex type, led to circulatory interaction between the centers.     

Electrophysiologic study of the cerebral control of swallowing

Swallowing dominant, created by serial pouring of water into rabbit's mouth cavity was tested in after-action from water supply. As a result of summation in the dominant focus of excitations elicited by stimuli of various modalities, swallowing took place. The study of swallowing dominant revealed by its stimulus which elicits its own unconditioned reflex (blinking), has shown that temporary feedback is characteristic for the dominant as well as for the conditioned reflex. Summation in the swallowing center during dominant testing by stimulation of the eye cornea takes place without conjugated inhibition of the blinking center. During discrete pouring of water into the animal's mouth, evoked potentials appear in the cortical-subcortical structures of the swallowing center. Identical potentials appear in corresponding structures before the summation swallowing. Appearance of these potentials in the electric activity of the dominant focus testifies to its readiness for summation.     

Conditioned food reflexes acquired on the basis of a dominant

By means of daily alimentary deprivation and presentation of acoustic stimuli, a hunger dominant was created in rabbits. After dominant testing by eye stimulation with air puff, when not only winking of one eye but also swallowing or chewing appeared,--the dominant was disrupted by giving food to the animal. Disruption of motivational hunger dominant led to rapid formation of stable temporary connection. At subsequent creation of hunger dominant the animal itself disrupted it by winking reaction with the significant eye. The basis of goal-directed reaction is the activation of feedback temporary connection, established at the dominant summation stage. The conditioned alimentary reflex, elaborated on the basis of dominant disruption is designated as endogenous alimentary conditioned reflex.     

Pharyngeal branch of the glossopharyngeal nerve plays a major role in reflex swallowing from the pharynx

Mechanical stimulation of the pharyngeal areas readily elicits reflex swallowing. However, it is much more difficult for electrical stimulation of the glossopharyngeal nerve (GPN) to evoke reflex swallowing than it is for stimulation of the superior laryngeal nerve (SLN) to do so. These paradoxical findings remain unexplained; hence, the main purpose of this study was to explain this contradiction by using a urethane-anesthetized rat. Mechanical stimulation easily elicited reflex swallowing from the pharynx. The posterior pillars, posterior pharyngeal wall, and the soft palate of the rat were extremely reflexogenic areas for swallowing. Sectioning the pharyngeal branch of the GPN (GPN-ph), however, eliminated the swallowing reflex from these areas. In contrast, sectioning the lingual branch of the GPN had no effect on the elicitation of swallowing. Electrical stimulation of the GPN-ph and SLN elicited sequentially occurring swallows. The relationship between stimulus frequency and the latency of swallowing for the GPN-ph was approximately the same as that for the SLN. These results indicate that the GPN-ph plays a major role in the initiation of reflex swallowing from the pharynx in rats.     

Effect of microelectrophoretic application of GABA on the formation of a cellular analog of a conditioned reaction

Influence of GABA application on ability of sensorimotor cortical neurones to form conditioned cellular reactions was studied in chronic experiments on rabbits. Neuronal reactions were analysed at the initial stage of eye-lid conditioning. GABA application in a period of presentation of paired conditioned and unconditioned stimuli disturbed formation of inhibitory conditioned cellular reactions and did not influence elaboration of activating responses. Plastic changes underlying the process of formation of inhibitory conditioned neuronal reactions are supposed to be of intracortical nature.     

BDNF-TrkB signaling interacts with the GABAergic system to inhibit rhythmic swallowing in the rat

Brain-derived neurotrophic factor (BDNF) acts as an anorexigenic factor in the dorsal vagal complex (DVC) of the adult rat brain stem. The DVC contains the premotoneurons controlling swallowing, a motor component of feeding behavior. Although rats with transected midbrain do not seek out food, they are able to swallow and to ingest food. Because BDNF and tropomyosin-related kinase B (TrkB) receptors are expressed in the DVC, this study hypothesized that BDNF could modify the activity of premotoneurons involved in swallowing. Repetitive electrical stimulation of the superior laryngeal nerve (SLN) induces rhythmic swallowing that can be recorded with electromyographic electrodes inserted in sublingual muscles. We show that a microinjection of BDNF in the swallowing network induced a rapid, transient, and dose-dependant inhibition of rhythmic swallowing. This BDNF effect appeared to be mediated via TrkB activation, since it no longer occurred when TrkB receptors were antagonized by K-252a. Interestingly, swallowing was inhibited when subthreshold doses of BDNF and GABA were coinjected, suggesting a synergistic interaction between these two signaling substances. Moreover, BDNF no longer had an inhibitory effect on swallowing when coinjected with bicuculline, a GABA(A) receptor antagonist. This blockade of BDNF inhibitory effect on swallowing was reversible, since it reappeared when BDNF was injected 15 min after bicuculline. Finally, we show that stimulation of SLN induced a decrease in BDNF protein within the DVC. Together, our results strongly suggest that BDNF inhibits swallowing via modulation of the GABAergic signaling within the central pattern generator of swallowing.     

High-Affinity Choline Uptake in the Hippocampus: Its Relationship to the Physiological State Produced by Administration of Barbiturates and Other Treatments

Abstract: Choline uptake in hippocampal synaptosomes was not inhibited by pentobarbital administration when rats were decapitated immediately upon loss of the righting reflex (3–4 min) even though it was inhibited at later times post-injection, when the rats were still unable to right themselves. Choline uptake was increased when the animals were decapitated at convulsion after an injection of picrotoxin, high doses of bicuculline, or one of the convulsant barbiturates. However, another convulsant barbiturate, as well as strychnine and lower doses of bicuculline, did not increase choline uptake even though the animals also convulsed. Thus loss of righting reflex or convulsion is not directly correlated with changes in choline uptake. At 7 min after injection, levels of pentobarbital in the hippocampus (and other brain regions) were correlated with the degree of inhibition of choline uptake up to about 50% inhibition; however, greater inhibition could not be achieved with much higher brain levels of the drug. Although hippocampal uptake was partially inhibited at 1 h after septal lesions, 3 h after the lesion the inhibition was no longer apparent. Inhibition was almost complete 10–12 days after the lesion. These results suggest that other factors in addition to impulse flow influence choline uptake.     

Respiratory neuronal activity during apnea and other breathing patterns induced by laryngeal stimulation

Respiration cycles through three distinct phases (inspiration, postinspiration, and expiration) each having corresponding medullary cells that are excited during one phase and inhibited during the other two. Laryngeal stimulation is known to induce apnea in newborn animals, but the cellular mechanisms underlying this effect are not known. Intracellular recording of ventral respiratory group neurons was accomplished in intact anesthetized, paralyzed, and mechanically ventilated piglets. Apnea was induced by insufflation of the larynx with ammonia-saturated air, smoke, or water. Laryngeal insufflation induced phrenic nerve apnea, stimulation of postinspiratory neurons, and stable membrane potentials in inspiratory and expiratory cells consistent with postinspiratory inhibition. Usually the membrane potential of each neuronal type cycled through an expiratory level before onset of the first recovery breath. Variants of the apnea response, probably reflecting the aspiration reflex or sniffing, sneezing, coughing, and swallowing, were also observed. These latter patterns showed oscillation between inspiration and postinspiration without an apparent intervening stage II expiratory phase. However, stage II expiratory activity always preceded onset of the first ramp inspiration after such a pattern. These findings suggest that activation of postinspiratory mechanisms causes profound alterations in the respiratory pattern and that stage II expiration importantly modulates recovery of ramp inspiratory activity. The mechanism of this latter effect may be inhibition of early inspiratory neurons with consequent postinhibitory rebound.     

The effects of the traditional chinese medicine, "Banxia Houpo Tang (Hange-Koboku To)" on the swallowing reflex in Parkinson's disease.

Swallowing disorder is common in Parkinson's disease (PD). We studied the swallowing disorder in PD, and tested the efficacy of Banxia Houpo Tang (BHT, a Chinese traditional medicine) in improving the swallowing reflex of PD patients. The Swallowing reflex test is a simple method used to detect swallowing disorders in patients with cerebrovascular disease. Because we observed previously that BHT significantly improved the swallowing reflex in cerebrovascular patients, we studied whether BHT was also effective in improving the swallowing disorder in patients with PD. 23 PD patients (13 males, 10 females, mean age 66.0+/-9.3, Hoehn & Yahr (H-Y) mean score = 2.8) were evaluated for swallowing reflex and the concentration of substance-P in their saliva before and after 4 weeks of BHT treatment. The swallowing reflex before treatment was significantly delayed, according to the H-Y score (Spearman's p = 0.014, R2 = 0.463). The swallowing reflex before BHT treatment was 3.66+/-0.98 sec, and after BHT treatment, it improved significantly, to 2.27+/-0.54 sec (p < 0.0001). Substance-P concentration in PD patients saliva before treatment was significantly lower than in healthy controls (p = 0.007), but showed no significant change after BHT treatment. Our research shows that the swallowing reflex is an effective method to evaluate the swallowing disorder in PD. BHT can significantly improved the swallowing reflex in PD patients, and therefore can be a hopeful candidate for preventing aspiration pneumonia in PD.     

Effects of steroid hormones on replication of murine sarcoma virus in mouse embryo cultures.

The androgenic steroid hormone, testosterone, inhibited focus formation by the murine Moloney sarcoma virus in mouse embryo cells. The inhibition of focus formation was enhanced by cyclic AMP. Although focus formation was inhibited, there was no inhibition of viral replication. The glucogenic adrenal corticosteroids, cortisol and dexamethasone, and 17-beta-estradiol and progesterone did not affect focus formation by MuSV(M).     

Interaction between two excitation foci in the central nervous system capable for summation

The interaction between two dominant foci was carried out on different models of dominant. It was shown that the following pairs: latent motor and blinking excitation foci; hunger and hypnotic dominants, decaying polarization dominant (related with functioning of the left-hemisphere) and hypnotic dominant can function simultaneously. After repeated formation of a new dominant focus against the background of the existing stable dominant created earlier, a replacement of dominants takes place. This process passes through the stage of formation of the latent dominant not yet apparent at the behavioral level but with the electrical activity typical for the dominant focus. Actually, two dominants exist at this stage: the previous active and latent foci. The latter determines further behavior of the animal.     

Multiple forms of non-associative plasticity in Aplysia: a behavioural, cellular and pharmacological analysis

A complete understanding of the cellular mechanisms underlying the formation of associations between stimuli, as occurs during classical conditioning, requires an understanding of the non-associative effects of the individual stimuli. The siphon withdrawal reflex of Aplysia exhibits both non-associative and associative learning when a tactile stimulus to the siphon serves as a conditioned stimulus, and tail shock serves as an unconditioned stimulus. In this chapter we describe experiments which examine the non-associative effects of tail shock at three different levels of analysis. At a behavioural level we found that the magnitude, and even the sign of reflex modulation induced by tail shock depended critically on three parameters: (i) the state of the reflex (habituated or non-habituated); (ii) the strength of the tail shock, and (iii) the time of testing after tail shock. Specifically, when non-habituated responses produced by water jet stimuli to the siphon were examined, tail shock produced transient inhibition 90 s later; facilitation of non-habituated responses (sensitization) only emerged after a considerable delay of 20-30 min. When habituated responses were examined, tail shock produced immediate facilitation (dishabituation); the amount of facilitation was inversely related to the strength of tail shock, with stronger shock producing no dishabituation. At a cellular level it was found that the complex excitatory postsynaptic potential (EPSP) in siphon motor neurons produced by water jet stimuli to the siphon provides a reliable cellular correlate of several of the non-associative effects of tail shock that we observe behaviourally. When non-decremented complex EPSPS were examined, strong tail shock produced transient inhibition at a test 90 s after shock.(ABSTRACT TRUNCATED AT 250 WORDS)     

Feedback regulation of the proliferation of the undifferentiated spermatogonia in the Chinese hamster by the differentiating spermatogonia

In the seminiferous epithelium the differentiating spermatogonia proliferate following a very strict synchronous pattern, and undergo the S phase during parts of particular epithelial stages. The undifferentiated spermatogonia do not divide synchronously and display maximum proliferative activity in stages XI-III. Hence the S-phase-specific cytotoxic agent Ara-C kills different proportions of these two cell types dependent on the epithelial stage. We have studied the effect of several combinations of degrees of cell loss to both compartments on proliferation of the undifferentiated spermatogonia. It was found that when the differentiating spermatogonia are removed, the proliferation of the undifferentiated spermatogonia is not inhibited at epithelial stage III, as seen in controls. However, when the undifferentiated spermatogonia were already arrested in G1, removal of the differentiating spermatogonia did not evoke proliferation again. When the population of undifferentiated spermatogonia was reduced in an area where the differentiating spermatogonia were left intact, the inhibition of the proliferation of undifferentiated spermatogonia took place around stage III as usual. It is concluded that in the normal adult seminiferous epithelium, the length of the period of active proliferation of the undifferentiated spermatogonia is regulated by negative feedback from the differentiating spermatogonia.     

The simplest form of emotional-motor reaction in man

In the present paper, human startle reaction (SR) characteristics were estimated by the amplitude of eye-lid reflex and extent of monosynaptic H-reflexes increase. SR depended not only on the parameters of sound stimulation (strength, unexpectedness) but also on the subject's functional state (attention, emotional background). Differences are given of the SR parameters from the orienting reaction. It is supposed that SR is an independent form of emotional-motor reaction of an adaptive character.     

Effects of protein synthesis on maturation, sperm penetration, and pronuclear development in porcine oocytes.

In vitro matured porcine oocytes were used to test the importance of protein synthesis for sperm penetration, the second meiotic division, and pronuclear development. Experiments were carried out to measure rates of protein synthesis in the presence of protein synthesis inhibitors (35 microM or 350 microM cycloheximide or a combination of inhibitors) (study 1); to test for sperm penetration and pronuclear development when protein synthesis was inhibited during fertilization (study 2); to test for oocyte meiosis, sperm penetration, and female and male pronuclear development when protein synthesis was inhibited during maturation (oocyte maturation in vitro with addition of inhibitor at 0, 24, or 36 hr of culture) (study 3); and to analyze the changes in the pattern of protein synthesis during these phases. Sperm penetration, oocyte meiosis, and female pronuclear development were not affected by the total inhibition of protein synthesis during fertilization. By contrast, inhibiting protein synthesis during maturation severely impaired the completion of meiosis and pronuclear development. Although inhibition of protein synthesis after 36 hr of maturation culture did not totally block male pronuclear development (MPN), the rate of MPN formation was lower than for controls (52% vs. 72%, P less than 0.05). However, protein synthesis was absolutely essential between 24 and 36 hr for the formation of MPN after decondensation. This period of maturation coincided with the dominant phase of protein reprogramming in the oocyte.     

Changes in endogenous level of auxins and cytokinins in axillary buds ofpisutn sativum L. in relation to apical dominance

Decapitation of the stem in one-week-old pea seedlings below the first node causes a rapid outgrowth of the two cotyledonary buds. One of them soon becomes dominant, while the other one is inhibited, but can be released from inhibition by cutting off the dominant bud. The level of endogenous auxins and cytokinins was determined in dominant and inhibited buds, as well as in released buds at different time intervals after deinhibition. It was found that the inhibited buds contained very little acidic, ether soluble auxins, a high level of tryptophan and also a high level of cytokinins, in comparison with dominant buds. When the inhibited buda were released from inhibition, their auxin content rose, while that of tryptophan and cytokinins decreased, reaching the level found in dominant buds within six days. Specific changes in content of two undetermined auxin-like substances were found in released buds during de-inhibition. These results are discussed in relation to the current views on the regulation of apical dominance.     

The effect of coupled cardiovascular and respiratory afferent signals on the central processes of human information processing

On the basis of contemporary knowledge on close functional connections between respiratory and cardiovascular afferents a computerized experimental device was developed by means of which central information processing can be studied in dependence on respiration phase and the level of baroreceptor activity. In all the examined parameters (time of motor reaction of two hands, latency of eye-lid reflex) the greatest changes were observed at maximum baroreceptor activity. These changes were clearly distinguished by direction during the phases of inhalation and exhalation. Such effect is probably based on the fact that the influence of cardiovascular afferents on the level of central activity is modulated in respiration rhythm through the mechanism of breath "gating" of postsynaptic STN structures.     

Capsaicin-sensitive muscle afferents modulate the monosynaptic reflex in response to muscle ischemia and fatigue in the rat

The role of muscle ischemia and fatigue in modulating the monosynaptic reflex was investigated in decerebrate and spinalized rats. Field potentials and fast motoneuron single units in the lateral gastrocnemious (LG) motor pool were evoked by dorsal root stimulation. Muscle ischemia was induced by occluding the LG vascular supply and muscle fatigue by prolonged tetanic electrical stimulation of the LG motor nerve. Under muscle ischemia the monosynaptic reflex was facilitated since the size of the early and late waves of the field potential and the excitability of the motoneuron units increased. This effect was abolished after L3-L6 dorsal rhizotomy, but it was unaffected after L3-L6 ventral rhizotomy. By contrast, the monosynaptic reflex was inhibited by muscle fatiguing stimulation, and this effect did not fully depend on the integrity of the dorsal root. However, when ischemia was combined with repetitive tetanic muscle stimulation the inhibitory effect of fatigue was significantly enhanced. Both the ischemia and fatigue effects were abolished by capsaicin injected into the LG muscle at a dose that blocked a large number of group III and IV muscle afferents. We concluded that muscle ischemia and fatigue activate different groups of muscle afferents that are both sensitive to capsaicin, but enter the spinal cord through different roots. They are responsible for opposite effects, when given separately: facilitation during ischemia and inhibition during fatigue; however, in combination, ischemia enhances the responsiveness of the afferent fibres to fatigue.     

Effect of ADP on the rate of acetyl phosphate hydrolysis by the Ca2+-ATPase of sarcoplasmic reticulum

Hydrolysis of acetyl phosphate is inhibited by high concentrations of Pi and MgCl2, probably due to an increase in the steady-state level of phosphoenzyme formed from Pi in the medium. A dual effect of ADP during steady-state hydrolysis of acetyl phosphate was observed. ADP inhibited hydrolysis in the presence of 5 mM MgCl2 and no added Pi, whereas it stimulated hydrolysis when phosphoenzyme formation by Pi was favored by including 6 mM Pi and 20 mM MgCl2 in the assay medium. ATP inhibited acetyl phosphate hydrolysis in both of these assay media. When phosphoenzyme formation by Pi in the presence of acetyl phosphate was stimulated at Ca2+ concentrations sufficient to saturate the low-affinity Ca2+-binding sites, ADP stimulated acetyl phosphate hydrolysis and also promoted ATP synthesis by reversal of the catalytic cycle. The rate of ATP synthesis was dependent on ADP, Pi and Ca2+. Phosphoenzyme formation by Pi and MgCl2, whether in the absence of Ca2+ and acetyl phosphate, or during acetyl phosphate hydrolysis, was inhibited by ADP and ATP. These results suggest that ADP interacts with different intermediates of the catalytic cycle and that expression of inhibition or activation of acetyl phosphate hydrolysis depends on the steady-state level of phosphoenzyme formed by Pi.