在α2氯醛糖麻醉的猫上, 结扎左心室冠状动脉前降支(LAD)一小分支, 对动物胆囊浆膜面予以缓激肽(BK), 可反射性地诱发血压、左心室内压升高、±dP/dtmax增大、心率加快,同时用超声单晶片声纳测微系统记录局部心壁运动, 发现BK可以反射性地引起LAD小分支远端所支配的心肌运动功能减弱。电针内关穴对BK诱发的升压反应有抑制作用, 并可改善局部心肌运动功能。静脉注射纳洛酮(014mg/kg) 能翻转电针效应。结果表明, 电针能够抑制BK诱发的升压反应和改善局部心肌运动功能, 该效应与内源性阿片肽有关。

The main source of expiratory drive to respiratory muscles in the rat is thought to be the caudal expiratory neurones. However, their projections to the spinal cord and the coordination of the population activity with the respiratory cycle are largely unknown. We examined their bulbospinal projections using antidromic activation, and the coordination of their activity using crosscorrelation. Of 76 expiratory neurones examined, 40% projected to the C2 segment of the spinal cord, all unilaterally and all but 4 to the contralateral side. Thirteen contralateral axons were located in the ventromedial funiculus, when activation thresholds were less than 25 μA. For 29 neurones, the mean (±SEM) conduction velocity, calculated from the single-point activation and a measure of the direct distance between recording and stimulating electrodes, was 7.4±0.4 m/s. We calculated 88 crosscorrelograms from ipsilateral pairs of expiratory neurones recorded on the same side of the medulla, and 176 contralateral pairs recorded from opposite sides of the medulla. All of the latter were featureless, but 23% of cross-correlograms for ipsilateral pairs displayed broad peaks at time zero, which we interpreted as due to activation of both neurones from a common source. We conclude that in the adult rat, approximately half of the caudal expiratory neurones project unilaterally and contralaterally to the spinal cord and, although common activation serves to coordinate some of the ipsilateral population, we suggest that neither common activation nor excitatory cross-connections exist as sufficient means for coordinating left and right populations to the same respiratory rhythm.

Inspiratory activity on the left and right sides must be coordinated to be effective. We used cross-correlation to examine the hypothesis that the coordination of left and right medullary inspiratory neurones is produced by excitation from common sources and by midline-crossing excitatory connections among these neurones. In adult rats, a total of 185 contralateral pairs of inspiratory neurones (n=370) were recorded extracellularly, and classified, according to their firing pattern, as augmenting (n=262), constant (n=82) or decrementing (n=26). Of the 262 augmenting inspiratory neurones, 98 were classified as phrenic premotor neurones by cross-correlation with phrenic nerve discharge. The 185 cross-correlograms showed little evidence of common activation, or midline-crossing excitatory connections. Of the 45 cross-correlograms for pairs of augmenting neurones, only 4 (≅9%) indicated a common activation, and only one a monosynaptic connection. Of the 45 for pairs of augmenting and phrenic premotor neurones, only 9 (20%) showed a common activation, and only 2 a monosynaptic excitatory connection. Of the 19 pairs of phrenic premotor neurones, 5 from the same rat showed high-frequency oscillations, and 1 a monosynaptic excitatory connection. Cross-correlograms for pair combinations of other types of neurones also exhibited few features. We suggest that, in the adult rat, although both common activation and excitatory cross-connections exexist as a means for coordinating left and right ventral group inspiratory neurones to the same respiratory rhythm, they are insufficient to account for it.

Hypoglossal nerve rootlets in the transverse medullary slice prepared from neonatal rats exhibit a bursting‘respiratory’rhythm that increases in frequency with CO2, presumably due to activation of chemosensitive cells such as the central chemoreceptors. Carbonic anhydrase is associated with areas of central chemoreception and we propose a hypothesis for its involvement in the chemoreception process. We tested this hypothesis by blocking its activity with acetazolamide in six slice preparations. However, the addition of 1 mM acetazolamide dissolved in dimethyl sulphoxide to the superfusing bathing solution produced no alteration in the bursting frequency response of the slice to CO2. We concluded that the chemoreception process producing the CO2 response of the superfused, transverse medullary slice does not involve carbonic anhydrase.

Circadian rhythms of heart rate variability have been widely studied in recent years. However, most previous reports described such rhythms in terms of normalized units of the low- and high-frequency (LF and HF) spectral components. In this study, we analyzed circadian rhythms of spectral components in absolute units and found unexpected results in normal subjects as well as coronary heart disease (CHD) and congestive heart failure (CHF) patient groups. The results indicate that the notion of sympathovagal balance needs to be re-evaluated.