Springer Science and Business Media LLC

Ở chuột cống, tình trạng ngộ độc rượu mãn tính gây ức chế quá trình tiết thần kinh và làm rối loạn nhịp sinh học bình thường của hoạt động các trung tâm tiết thần kinh trong vùng dưới đồi.

The hypothesis that decreases in brain blood flow during respiration of hyperbaric oxygen result from inactivation of nitric oxide (NO) by superoxide anions (O2 –) is proposed. Changes in brain blood flow were assessed in conscious rats during respiration of atmospheric air or oxygen at a pressure of 4 atm after dismutation of O2 – with superoxide dismutase or suppression of NO synthesis with the NO synthase inhibitor L-NAME. I.v. administration of superoxide dismutase increased brain blood flow in rats breathing air but was ineffective after previous inhibition of NO synthase. Hyperbaric oxygenation at 4 atm induced decreases in brain blood flow, though prior superoxide dismutase prevented hyperoxic vasoconstriction and increased brain blood flow in rats breathing hyperbaric oxygen. The vasodilatory effect of superoxide dismutase in hyperbaric oxygenation was not seen in animals given prior doses of the NO synthase inhibitor. These results provide evidence that one mechanism for hyperoxic vasoconstriction in the brain consists of inactivation of NO by superoxide anions, decreasing its basal vasorelaxing action.

An increase in synchronization of the activational type (coincidence of the presence of impulse activity), and a decrease of the inhibitory type (coincidence of both the presence and absence of impulse activity), in the operation of close-lying neurons were observed in the visual and sensorimotor areas of the new cortex and in the hippocampus of wakeful non-immobilized rabbits in response to the combination of flashes of light with electrodermal stimulation (EDS) of the extremity. An increase in the synchronization of the neurons of the inhibitory type took place in the visual cortex in response to flashes against the background of the conditional inhibitor, i. e., continuous light, and changes in synchronization, similar to the effect of pain reinforcement but significantly weaker, appeared in the sensorimotor cortex and in the hippocampus. An increase in synchronicity of the activational type took place primarily in pairs of neurons with increase in the same direction in the frequency of impulse activity in response to a stimulus, and of the inhibitory type, took place with its decrease. In addition, both kinds of changes in synchronization appeared in a significant portion of the pairs of neurons with changes in the frequency of impulse activity of different directions.

Experimental studies on intact nodes of Ranvier in isolated nerve fibers led to the conclusion that the accumulation of K+ ions released into the perinodal space during excitation performs a series of important functions: it decreases K+ release from the axoplasm, induces prolonged post-spike depolarization and its associated exaltation phase, underlies repeated and rhythmic activity, activates the electrogenic membrane Na+,K+-pump, and determines the generation of the prolonged component of post-tetanic hyperpolarization, which is an additional factor responsible for reabsorption of potassium ions into the cytoplasm of nerve fibers, etc.

Gravitational unweighting is known to induce atrophy and to suppress proliferative processes in the postural muscles; muscle stretching during unweighting allows this atrophy to be overcome. It has been suggested that stretching of the soleus muscle promotes proliferation of satellite cells with subsequent incorporation of their nuclei into fibers on functioning loading of the hindlimbs in rats. The numbers of satellite cells labeled with M-cadherin on cross-sections of single fibers were assessed. After two weeks of antiorthostatic suspension, the number of labeled cells decreased by 33% from the level seen in the control group. In passive stretching, the number of labeled cells was 2.5 times greater than that in suspended animals and 1.7 times greater than in that control animals. The key role in the activation of satellite cells is known to be played by growth factors, including insulin-like growth factor I (IGF-I). Levels of IGF-I expression were measured in the soleus muscle after suspension with stretching, which showed no changes as compared with the suspension without stretching or control groups. Thus, these experiments demonstrated that passive stretching stimulates increases in the proliferation of satellite cells in the soleus muscle of the stretched limb in rats as compared with the level seen in normal conditions, with no changes in the expression of IGF-I or its splice variant MGF.