Improved methods for researching isolated carotid sinus baroreceptors automatically controlling for sinus pressure / 中国应用生理学杂志

<p><b>OBJECTIVE</b>To develop a system for automatically controlling carotid sinus pressure in the study on baroreceptors.</p><p><b>METHODS</b>The preparation containing carotid sinus with parts of the connected vessels and carotid sinus nerve (CS-CSN) were isolated and perfused. A critical pressure controlling component (PRE-U, Hoerbiger, Deutschland) dictated by a computer was integrated into the system to clamp the intrasinus pressure. The pressure command and the relevant intrasinus pressure were compared to evaluate the validity of the pressure controlling system.</p><p><b>RESULTS</b>A variety of sinus pressure-controlling patterns, including pulsation, ramp and step pressures, could be achieved accurately by using the system, and the pressure-dependent discharge activities of sinus nerve were confirmed.</p><p><b>CONCLUSION</b>This system for clamping carotid sinus pressure could realize multiple pressure-controlling patterns and is a useful and flexible pressure controlling method that could applied in the study on mechano-electric transduction of baroreceptors.</p>

The effects of repetitive limb ischemia on the systemic concentration of NO, NOS in plasma of healthy humans / 中国应用生理学杂志

<p><b>AIM</b>To investigate the effects of RLI on plasma nitric oxide (NO) and NO synthase (NOS) isoforms of healthy humans.</p><p><b>METHODS</b>30 healthy human subjects (aged from 40 - 70 years old) were recruited. RLI was induced by five 5 min cycles of ischemia of non dominant arm (200 mmHg, 5 min interval). Blood pressure, heart rate, and the feelings of ischemic arm were continuously monitored. Venous plasma was collected in contralateral arm at Pre, Post-0 h, Post-4 h, and Post-24 h. Plasma level of NO was measured by Griess reaction, and NOS was measured by chemical method.</p><p><b>RESULTS</b>Blood pressure and heart rate varied in normal range. The uncomfortable feeling was decreased with the increasing numbers of ischemic cycles. Plasma level of NO, and iNOS in plasma were significantly increased at Post-0 h, Post-4 h, and Post-24 h compared to Pre (P < 0.05). tNOS was also significantly increased at Post-0 h and Post-4 h compared to Pre (P < 0.05). No significant change in plasma cNOS was shown at following three time points than Pre.</p><p><b>CONCLUSION</b>These findings suggest that RLI can elevate plasma level of NO, tNOS, and iNOS in healthy humans. RLI might be a safe method as a rIPC, and it would have important possibility to be performed in clinic.</p>

Arrhythmia triggered by stretching rabbit left ventricles and the block effect of streptomysin / 中国应用生理学杂志

<p><b>AIM</b>To observe the effect of stretching left ventricles in the end of action potential on rabbit cardiac activity, and to investigate its possible mechanisms.</p><p><b>METHODS</b>Stretch (120 mmHg, 50 ms) was applied in the end of action potential by the pressure-clamp technique to observe if there would be any changes in rabbit cardiac activity and streptomycin (500 micromol/L) was used to identify the mechanism.</p><p><b>RESULTS</b>Stretch in the end of action potential caused arrhythmia (P < 0.05) and streptomycin blocked the above effect (P < 0.05).</p><p><b>CONCLUSION</b>Streptomycin could block the effect of stretching left ventricles in the end of action potential on rabbit cardiac activity, which indicates that stretch-activated ion channels involve it.</p>

A ventricular pressure-clamping system for the study of mechano-electrical feedback / 生理学报

It is necessary to control the mechanical stimuli precisely in the studies of cardiac mechano-electrical feedback (MEF). In the present study a ventricular pressure-clamping system has been developed, which can be applied to isolated-perfused rabbit hearts. Controlled by a computer, this system not only can make the left ventricle follow a command defining the same pressure wave as that during a beating cycle under physiological condition, but also deliver mechanical stimuli with a proper waveform to the ventricle at a particular time phase. This system integrates multiple functions, including perfusing, pacing, recording of electrocardiogram and monophasic action potentials, and clamping and measuring of ventricular pressures in isolated-perfused hearts. Thus, it is a distinct system for investigating the phenomena and mechanisms of cardiac MEF at organ level.

Effects of calcitonin gene-related peptide on repolarization process in isolated guinea-pig atrial myocardium at the physiological temperature / 生理学报

The purpose of this study was to investigate the effects of calcitonin gene-related peptide (CGRP) on the repolarization process in isolated guinea-pig atrial cells and to determine the contribution of K(+) channels to the CGRP-induced changes in action potential using conventional microelectrode method at the physiological temperature. We found that: (1) CGRP (16 nmol/L) antagonized the influences of potassium channel blockers, 4-AP and BaCl2, on action potential; (2) CGRP (16 nmol/L) increased the amplitude and maximum depolarizing velocity of slow action potential and shortened the conducting time in guinea pig atrial myocardium at extracellular K(+) concentration of 18.5 mmol/L; (3) CGRP (16 nmol/L) alleviated triggered activity induced by superfusion with solution containing CsCl and no potassium ion; and (4) the effects of CGRP on the configuration of action potential were temperature-dependent. At the temperature of 36.5+/-0.5 degrees C, CGRP (5, 16, and 50 nmol/L) increased the amplitude of the action potential and shortened APD(20), APD(50) and APD(90). The CGRP effects on APD(20) and APD(50) were dose-dependent and reversible. On the contrary, CGRP prolonged APD(20), APD(50) and APD(90) at the temperature of 25.5+/-2.1 degrees C. The present study suggests that CGRP possesses multiple effects on various ionic channels. Among them the effects on potassium currents are major determinants in the changes in action potential induced by CGRP under physiological temperature. It is necessary to further study the influences of CGRP on different types of potassium channels.