ABSTRACT
OBJECTIVE: To further disclose mechanisms in adaptation of pulmonary and systemic arteries to simulated microgravity (SM), so as to elucidate the mechanisms accounting for orthostatic intolerance after SM, and to explore a new kind of countermeasure for orthostatic intolerance. METHOD: 300 tail suspended (TS) rats were used as the model to simulate the physiological effects of microgravity. Vasoreactivity changes of rings sectioned from pulmonary artery (PA) and thoracic aorta (TA) to 68 mmoles/L KCl, plus phenylephrine (PE) and acetylcholine (ACh) were observed after 7 d and 14 d tail-suspension. After preconditioning with 10(-5) moles/L N-nitro-L-arginine methyl ester (L-NAME) for 20 min, vasoreactivity changes of PA and TA to PE and ACh were respectively repeated. RESULT: The contractile responsiveness of PA and TA to KCl and PE decreased significantly or very significantly after TS7 d and TSI4 d. The dilatory reactivity of PA and TA to ACh after TS7 d had a significant or very significant increase, but reactivity of PA showed no change and TA showed only a tendency to increase after TS14 d. After preconditioning with 10(-5) moles/L L-NAME, responsiveness of PA to PE after TS7 d and TS14 d had no difference among the three groups, but responsiveness of TA to PE after TS7 d and TS14 d had a significant decrease. The dilatory reactivity of PA after TS7 d decreased significantly or very significantly, and the remains showed no significant change. CONCLUSION: The decrease of contractile responsiveness of PA and TA might be due to the increased dilatory function of the endothelial cells. The fact that 10(-5) moles/L L-NAME reversed the decrease of contractile responsiveness of PA and partly of TA after tail suspension implicates that there might be an inhibitory action on the dilatory function of the endothelial cells. The NOS inhibitors may be helpful in preventing orthostatic intolerance.
Subject(s)
Aorta, Thoracic/physiology , Endothelium, Vascular/physiology , NG-Nitroarginine Methyl Ester/pharmacology , Pulmonary Artery/physiology , Vasoconstriction/physiology , Weightlessness Simulation , Acetylcholine/pharmacology , Animals , Aorta, Thoracic/drug effects , Aorta, Thoracic/metabolism , Endothelium, Vascular/drug effects , Endothelium, Vascular/metabolism , Enzyme Inhibitors/pharmacology , Hindlimb Suspension , Hypotension, Orthostatic/metabolism , Nitric Oxide Synthase/pharmacology , Phenylephrine/pharmacology , Pulmonary Artery/drug effects , Pulmonary Artery/metabolism , Rats , Rats, Wistar , Time Factors , Vasoconstriction/drug effects , Weightlessness CountermeasuresABSTRACT
Objective. To study the difference between two types of event-related brain potentials (ERPs) in auditory location discrimination task. Method. Event-related potentials (ERPs) in auditory location discrimination task were recorded in 14 normal subjects and were compared with head-down tilt (HDT) and head-up tilt (HUT) conditions. Result. 1) The subjects could be divided into group I (n=7) and group II (n =7) according to the feature of the target ERPs component (P3). The difference between the two groups was mainly that there was a negative slow wave after 150 ms in the ERPs of group II subjects, and that the reaction time and error rate in II group was higher than in I group. These data indicated that the psychological load on group II was larger than that on group I. 2) The reduction of mean slow potential amplitude during HDT was more significant in group II than in group I. Conclusion. The slow potential amplitude of ERPs may reflect the psychological load and the brain function state. Attention should be paid to the feature of auditory ERPs in space medical practice.
Subject(s)
Discrimination, Psychological/physiology , Evoked Potentials, Auditory/physiology , Head-Down Tilt , Sound Localization/physiology , Weightlessness Simulation , Acoustic Stimulation , Adult , Auditory Perception , Electroencephalography , Ergonomics , Humans , Reaction TimeABSTRACT
Objective. To study N2 effect and its feature on non-target event-related brain potentials during auditory selective attention. Method. The subjects were 16 healthy right-handed male volunteers aged 23.2 +/- 2.1 years. The stimuli were male voice of one-digit numbers (2 to 7), which were single syllable pronunciated in Chinese, and appeared randomly with equal probability. The subjects were asked to press a switch as soon as the target signal (odd or even number) was heard but make no response to the non-target signal. EEG signals at 9 locations were recorded. Result. 1) A negative component N280 (N2 effect) was found after non-target stimuli as compared to target stimuli, which was significant in the frontal brain locations; 2) P3 was smaller and its peak appeared later in non-target ERPs than in target ERPs. Conclusion. N2 effect was also elicited by non-target stimuli during auditory modality. We assume that N2 effect might reflect the readjusting of model stored in working memory at the frontal brain.