Effects of electroacupuncture stimulation applied to limb and back on mesenteric microvascular hemodynamics

The effects of electroacupuncture stimulation (EAS) of the hind paw and the back on the mesenteric microhemodynamics in anesthetized rats were investigated using an intravital microscope system. Red blood cell (RBC) velocity in the mesenteric arterioles was measured by the dual-sensor method developed by the authors. Electrical stimulation was applied using two acupuncture needles inserted into the skin and the underlying muscles of the hind paw and the dorsal Th13-L1 level area. The hind-paw EAS evoked intensity-dependent pressor responses and increase responses in RBC velocity in mesenteric precapillary arterioles, while the back EAS evoked depressor responses and decrease responses in RBC velocity. Heart rate showed increase responses accompanying EAS either on the hind paw or the back. The pressor responses and increase responses in RBC velocity in mesenteric precapillary arterioles accompanying the hind paw EAS were abolished by an intravenous administration of alpha-adrenergic receptor antagonist (phenoxybenzamine; POB), and the tachycardiac responses were abolished by administration of beta-adrenergic receptor antagonist (propranolol). Occasional but notable reflex vasoconstrictions in the mesenteric terminal arteriole were induced by EAS either on the hind paw or the back. These vasoconstrictive responses were not affected by the administration of POB. The present study directly demonstrated that hemodynamic changes at the level of precapillary arterioles accompanying EAS either on the hind paw or the back mainly depend on the changes of systemic arterial pressure regardless of stimulus current intensities. Moreover, the results in the present study suggest some receptors other than alpha-adrenergic receptor might be involved in the mechanism of EAS-induced vasoconstriction in the mesenteric arteriole.     

Reduction in inflammation-induced sensitization of dorsal horn neurons by transcutaneous electrical nerve stimulation in anesthetized rats

Transcutaneous electrical nerve stimulation (TENS) is utilized to treat a variety of painful conditions. Inflamed animals present with an increased response to noxious stimuli, i.e., hyperalgesia, at the site of injury (primary hyperalgesia) and outside the site of injury (secondary hyperalgesia). Further, following acute inflammation, dorsal horn neurons show an increased responsiveness to peripherally applied stimuli, which has been termed sensitization. Previous studies demonstrate a reduction in dorsal horn neuron activity following TENS treatment in normal animals and a reduction in primary and secondary hyperalgesia in acutely inflamed animals. The purpose of this study was to examine the effects of TENS on dorsal horn neurons sensitized by acute inflammation. Extracellular recordings from wide dynamic range (WDR), high threshold (HT) and low threshold (LT) dorsal horn neurons in anesthetized rats were assessed for spontaneous activity, responses to innocuous and noxious mechanical stimulation and receptive field size. Responses were measured before and 3 h after induction of inflammation, and immediately and 1 h after application of either high (100 Hz) or low (4 Hz) frequency TENS (motor intensity, pulse duration = 100 microseconds). TENS was applied to the inflamed paw to encompass the receptive field of the neuron for 20 min. WDR and HT dorsal horn neurons sensitized to mechanical stimulation after induction of inflammation. Application of either high or low frequency TENS to the inflamed paw reduced both innocuous and noxious evoked responses of WDR and HT dorsal horn neurons immediately and 1 h after treatment with TENS. Comparison of responses after TENS with baseline responses showed that the evoked responses in the majority of WDR and HT cells returned to or fell below baseline responses. TENS had no effect on responses of LT neurons. In summary, central neuron sensitization is reduced by TENS and may underlie the reduction in hyperalgesia observed after treatment with TENS.     

Responses of dorsal spinal cord blood flow to noxious mechanical stimulation of the skin in anesthetized rats

In urethane-anesthetized, artificially ventilated rats, alterations in dorsal spinal cord blood flow (SCBF) at the L4-6 level were measured with laser Doppler flowmetry in response to noxious mechanical cutaneous stimulation (pinching) of either a forepaw or a hindpaw. The stimulation was delivered ipsilaterally or contralaterally to the site of blood flow measurement. Pinching of the forepaw or the hindpaw on either side increased mean arterial pressure (MAP) to the same degree. However, the SCBF response to pinching of the ipsilateral hindpaw was significantly greater than that to other stimulations. These responses were not influenced by denervation of the baroreceptors. The responses of SCBF to pinching of the ipsilateral hindpaw persisted both after treatment with phenoxybenzamine and after spinalization at the C1-2 level, whereas the responses to pinching at other sites disappeared. The responses of MAP to stimulation at all four sites became negligible after treatment with phenoxybenzamine and after spinalization at the C1-2 level. These results indicate that noxious mechanical stimulation of the skin produces increases in SCBF via two mechanisms: one is via an elevation of systemic arterial pressure; the other is via a localized spinal mechanism evoked by ipsilateral, segmental inputs.     

Influence of ethanol on systemic and pulmonary hemodynamics in anesthetized dogs

Immediate circulatory reactions to acute intragastric ethanol administration were studied by a catheterization technique in spontaneously breathing dogs. Diluted ethanol was given in a dosage of 1 g/kg in test group I (n = 11), and 2 g/kg in group II (n = 10). The control group (n = 14) received only water. The highest blood ethanol concentration was 0.90 ± 0.07 mg/ml (mean ± SE) in group I, and 1.97 ± 0.10 mg/ml in group II. Heart rate and cardiac output increased (p < 0.001), but stroke volume, mean aortic blood pressure and right atrial blood pressure remained practically unchanged. Systemic vascular resistance decreased. Mean pulmonary arterial blood pressure increased markedly in both test groups (p < 0.001) while pulmonary arterial wedge pressure did not change. The pulmonary arterial resistance increased (p xyl 0.01). Changes in respiratory rate or volume and arterial pO₂ were negligible in group I, but respiratory minute volume decreased in group II. In conclusion, ethanol in concentrations 0.5 to 2.0 mg/ml increased resistance in the pulmonary arterial tree, indicating pulmonary arterial vasoconstriction, but reduced systemic vascular resistance, thus putting a concept of peripheral vasodilation in favour.     

Effects of electrical stimulation of vagal nuclei in anesthetized and unanesthetized cats

Changes in the heart rate were studied during stimulation of the effector nuclei of the vagus nerves — the dorsal vagal nucleus and the nucleus ambiguus — in anesthetized and unanesthetized cats. If groups of neurons, stimulation of which in anesthetized cats causes slowing of the heart, were stimulated in unanesthetized cats under conditions of free behavior, the heart rate was increased. Pharmacological- adrenergic receptor blockade by injection of Obsidan or Inderal (propranolol) demonstrated the parasympathetic nature of these effects. The fact that that they are parasympathetic in nature was also confirmed by the character of the response: its short latent period and rapid disappearnce of the effect after removal of the stimulation.Translated from Fiziologicheskii Zhurnal SSSR imeni I. M. Sechenova, Vol. 62, No. 3, pp. 382–386, March, 1976.     

电刺激对背根神经节和雪旺细胞髓鞘化的影响

目的:建立体外的背根神经节（DRG）—雪旺细胞（SCs）—电刺激模型,为研究电刺激促周围神经成髓鞘机制提供基础。方法:以函数发生器和电刺激小室构建电刺激细胞培养系统,DRG/SCs共培养24 h后分为对照（Ctrl）组和电刺激（ES）组。ES组给予矩形波电刺激,6 Vp-p,10 Hz,1 h/d,7 d。Ctrl组无电刺激。利用CCK8观测电刺激对细胞毒性的影响,利用髓磷脂碱性蛋白（MBP）免疫荧光检测电刺激对DRG/SCs髓鞘化的影响。结果:CCK8细胞增殖毒性实验显示,ES组光密度值略高于Ctrl组,但两组之间无统计学意义。免疫荧光检测结果显示ES组MBP的荧光强度明显高于Ctrl组（P<0.01）。结论:本文设计的电刺激细胞培养系统对神经细胞安全无毒,连续7 d的电刺激可提高神经髓鞘化率。     

Effects of chronic intermittent hypoxia on the hemodynamics of systemic circulation in rats

We examined the effects of chronic intermittent hypoxia (IH) on the hemodynamics of systemic circulation in rat. Chronic IH has no effect on the hemodynamics in the normoxia condition, but it could effectively prevent the fall of hemodynamics during acute hypoxia.     

Electro-acupuncture stimulation effects on duodenal motility in anesthetized rats

The effect of electro-acupuncture stimulation (EAS) on duodenal motility was examined in anesthetized, artificially ventilated rats. EAS was applied to the abdominal area or to a hindpaw for 30 s at stimulus intensities of 0.1-10.0 mA with a stimulus frequency of 20 Hz. The duodenal motility was measured using the balloon method at a position about 1.5 cm caudal from the pylorus. Duodenal motility was inhibited by EAS at intensities of more than 5.0 mA (suprathreshold of group IV afferent excitation) when applied to the abdominal area. The duodenal inhibitory response existed after bilateral vagotomy or spinal transection, but was abolished by sectioning bilateral splanchnic nerves. Duodenal motility was facilitated by EAS at intensities of more than 2.0 mA (subthreshold of group IV, and suprathreshold for groups II+III afferent excitation) when applied to a hindpaw. The duodenal facilitatory response by EAS to a hindpaw existed after sectioning the splanchnic nerves, but disappeared after bilateral vagotomy or spinal transection. Furthermore, repetitive electrical stimulation of vagal efferent nerves enhanced duodenal motility, while repetitive electrical stimulation of the splanchnic efferent nerves inhibited the motility. It was concluded that the inhibitory response of duodenal motility elicited by EAS to the abdominal area is a spinal reflex response involving splanchnic inhibitory efferent nerves, and the enhanced response of duodenal motility by EAS to a hindpaw is a supraspinal reflex response involving vagal excitatory nerves.     

Influence of electrical stimulation of the posterior hypothalamus on musculocutaneous and renal circulation in anesthetized dogs

Summary Hypertension and tachycardia were consistently induced by electrical stimulation of the median posterior hypothalamus in dogs under chloralose anesthesia, curarized and artificially ventilated. When renal and femoral vascular beds were perfused at a constant blood flow, the renal perfusion, pressure markedly increased, whereas only minor variations of the femoral perfusion pressure occurred. When the renal and femoral vessels were perfused by the heart at the prevailing blood pressure, peri-arterial electromagnetic flow measurements revealed that renal flow decreased and that femoral flow increased during hypothalamic hypertension, both before and after vagotomy. In the same animals, no significant changes of renal or femoral flow occurred during reflexogenic hypertension induced by carotid occlusion. These marked hemodynamic differences between the reflexogenic and the hypothalamic type of hypertension were consistently and repeatedly observed. The indications that baroreflex counter-regulation and ganglionic inhibition due to elevated catecholaminemia contribute to the relative lack of femoral vasoconstriction during hypothalamic hypertension, are discussed.Partly supported by grant nr. 2034 from I.W.O.N.L., Belgium     

Reconstruction of dorsal skin scars in rats

Laboratory of Growth and Development, Institute of Human Morphology, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR, Permyakov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 112, No. 8, pp. 217–219, August, 1991.     

Photoacoustic microscopy of microvascular responses to cortical electrical stimulation

Advances in the functional imaging of cortical hemodynamics have greatly facilitated the understanding of neurovascular coupling. In this study, label-free optical-resolution photoacoustic microscopy (OR-PAM) was used to monitor microvascular responses to direct electrical stimulations of the mouse somatosensory cortex through a cranial opening. The responses appeared in two forms: vasoconstriction and vasodilatation. The transition between these two forms of response was observed in single vessels by varying the stimulation intensity. Marked correlation was found between the current-dependent responses of two daughter vessels bifurcating from the same parent vessel. Statistical analysis of twenty-seven vessels from three different animals further characterized the spatial-temporal features and the current dependence of the microvascular response. Our results demonstrate that OR-PAM is a valuable tool to study neurovascular coupling at the microscopic level.     

Effect of electrical stimulation of the mamillary nuclei of the hypothalamus on skin vessel permeability in intact and capsaicin-treated rats

Stimulation of the mamillary nuclei of the rat hypothalamus induced increases in the permeability of forelimb skin microvessels. This effect was not seen in rats stimulated after administration of capsaicin at a dose (150 mg/kg) sufficient to deplete vasoactive neuropeptides from the peripheral nerve terminals of capsaicinsensitive neurons. These data indicate a role for the mamillary nuclei in central mechanisms modulating the effector functions of primary capsaicin-sensitive neurons. Laboratory of Functional Neuromorphology, Institute of Physiology, Siberian Division, Russian Academy of Medical Sciences, 6 Academician Timakov Street, 630117 Novosibirsk, Russia. Translated from Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 82, No. 12, pp. 1–5, December, 1996.     

Effect of electroacupuncture on systemic hemodynamics in rats with postinfarction cardiosclerosis

Electroacupuncture decreased total peripheral vascular resistance and increased cardiac output in 12-week-old postinfarction rats without cardiac insufficiency, while opposite changes were observed in rats with cardiac insufficiency. After the electroacupuncture course, norepinephrine decreased cardiac output in the rats with cardiac insufficiency, while acetylcholine increased it to a much higher extent than in the control rats that were not subjected to physiotherapy. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 127, No. 1, pp. 29–34, January, 1999