Effect of vasopressin and enkephalin analogs on the chemoreactive properties of the sensorimotor cortex neurons in rats

On immobile rats it has been shown that subcuteneous injection of two different neuropeptides causes different distribution of activating, inhibiting and areactive cells resulting from microionoforetically administrated acetylcholine and noradrenaline without altering the mean frequency of the background unit activity sensorimotor cortical neurons. At the same time the alteration in the pattern of neurons impulse activity has been revealed, which acquires the character of packet activity with a specific packet length of 2-3, 4-6, 7-10 impulses. Depending on the injected neuropeptide reliable but almost contrary effects of the packet activity alterations have been observed. These effects have been suggested to result from the alteration of the chemoreactive properties of the neuron membranes and the corresponding reorganisations of interneuron attitudes.     

Effect of thymalin and heterotransfusion on blood coagulation and fibrinolysis in thymectomized rats

Experiments on rats have shown that thymectomy brings about the development of hypercoagulation and inhibition of fibrinolysis. Heterotransfusion is accompanied by hypocoagulation and stimulation of fibrinolysis in both intact and thymectomized rats. At the same time fibrinolysis in thymectomized rats is stimulated to a lesser degree than in intact animals. Preinjection into thymectomized rats of the thymus low-molecular factor thymaline over one week does not only make blood coagulation and fibrinolysis return to normal but also leads to adequate changes in the hemostatic system in response to heterotransfusion.     

Analysis of the dual mechanism of ACTH release by arginine vasopressin and its analogs in conscious rats

Plasma ACTH and/or corticosterone levels were measured in conscious rats 30 min after subcutaneous administration of arginine vasopressin (AVP), oxytocin (OT) and various analogs with a large range of activity on the vasopressor (V1), antidiuretic (V2) or oxytocic receptors. The comparison of their dose-response curves indicated that two different mechanisms are involved in the release of ACTH by neurohypophysial peptides and their analogs. AVP itself and a specific vasopressor agonist (Phe2, Orn8, OT) displayed a similar, high slope dose-response curve. Non-vasopressor analogs, such as dDAVP were characterized by a low slope dose-response curve. Furthermore, dDAVP potentiated CRF and neither its own ACTH-releasing action nor its potentiation of CRF were sensitive to previous VI- or V2-receptor blockade. These results, together with other available data, are interpreted as indicative of the existence of two mechanisms of action for ACTH release by AVP and its analogs in vivo: an indirect action via endogenous CRF release, mediated by a VI receptor mechanism, and a direct action on the pituitary, shared by dDAVP and other non-vasopressor analogs, with receptor characteristics different to both the V1 and the V2 classical types.     

Effect of coccidiosis on blood coagulation in broilers

Severe infection with Eimeria acervulina, Eimeria maxima, Eimeria necatrix, and Eimeria tenella increased the prothrombin times in broilers compared with the times in uninfected birds. Recalcification time was not affected. The increase in prothrombin time was related to the severity of infection (as measured by lesion score), and was significant (P less than or equal to 0.05) only in the most severely infected birds. The increase was of short duration, lasting only 1 or 2 days, and first appeared on day 5 or 6 postinoculation. Restricting the feed intake of uninoculated birds to the amount of feed consumed by infected birds showed that the reduction in feed intake with coccidiosis was not responsible for the increase in prothrombin time.     

Effect of norepinephrine and vasopressin on renal kallikrein excretion in rats

The purpose of this study was to investigate the effect of norepinephrine and vasopressin on urinary kallikrein excretion in the rat. Two studies were undertaken: (a) acute experiments in which the rats were infused with 30% dextrose in water with the addition of norepinephrine or vasopressin, (b) chronic experiments in which the drugs were infused during seven days through an osmotic minipump. In acute experiments, urinary kallikrein excretion increased without modification in urinary flow and glomerular filtration rate. In chronic experiments, urinary kallikrein excretion was not modified in norepinephrine-treated rats and decreased in vasopressin-infused animals. This decrease followed the modifications of the urine flow. In chronic experiments the dextrose infusion increased urinary kallikrein excretion. In all the groups studied a positive correlation between urine flow and urinary kallikrein excretion was observed. It is concluded that norepinephrine and vasopressin are important stimulators of the urinary kallikrein excretion only in those circumstances where it is necessary to eliminate an excess of water.     

Effect of intraventricular oxytocin and vasopressin on self-stimulation in rats.

Oxytocin (500 mu u) and vasopressin (50 mu u) were injected into the lateral ventricle and its effect on hypothalamic self-stimulation has been studied. Oxytocin increased, while vasopressin decreased the self-stimulation rate tested 10-20 min following application. The hypothalamic and mesencephalic serotonin content decreased slightly while plasma corticosterone content did not change 20 min after oxytocin and vasopressin administration compared to the injected control animals. The data suggest that vasopressin and oxytocin have an opposite effect on self-stimulation and this action is not mediated through the brain serotoninergic or pituitary-adrenocortical axis.     

他克莫司对大鼠血糖的影响及其作用机制

目的 观察不同浓度的他克莫司对大鼠血糖的影响.方法 选取雄性SD大鼠30只,体重70～85g,随机等分为三组.A组大鼠为他克莫司加五脂胶囊组,每日给予他克莫司(普乐可复Astellas Ireland Co.,Ltd生产)2 mg/kg和五酯软胶囊(四川光大制药有限公司生产)0.2粒/kg;B组为他克莫司组,每日给予他克莫司2 mg/kg;C组为对照组,每日给予同等量生理盐水,三组大鼠均在空腹时灌胃给药,用药1h后喂食.用药时间为5个月.每月监测大鼠他克莫司血药浓度和空腹血糖.结果 在用药的1～5个月期间,A组大鼠他克莫司血药浓度均明显高于B组.在用药的第1个月和第2个月,三组大鼠空腹血糖无明显差异(P＞0.05),用药第3个月后,A、B两组大鼠血糖均明显高于对照组(P＜0.01),A组大鼠血糖略高于B组,二者之间差异并无统计学意义(P＞0.05);用药第4、5个月后A、B两组大鼠的血糖持续升高,并且A组大鼠血糖明显高于B组(P＜0.01);A组的胰岛素分泌指数和敏感指数均明显低于C组(P＜0.01).结论 他克莫司通过减少胰岛素的分泌、增加胰岛素抵抗导致大鼠血糖升高,这种升血糖作用呈时间依赖性和浓度依赖性.     

Opposite effects of intraventricular and intracisternal administration of vasopressin on blood pressure in rats

Lysine-8-vasopressin (LVP) was injected into the lateral ventricle (ICV) or into the cisterna magna (c.m.) of ether-anesthetized rats. ICV injection of LVP decreased the blood pressure (BP), whereas c.m. administration increased it. The opposite effects of ICV versus c.m. administration of the peptide might be related to differences in brainstem versus limbic-midbrain structures in the regulation of blood pressure, and suggest that both mechanisms can be influenced by vasopressin.