Melatonin‐evoked potentiation of the juvenile rat tail artery neurogenic reactivity depends on degree of the change in the reactivity

Aim: Dependence of the melatonin‐evoked potentiation of the rat tail artery neurogenic reactivity on degree of the change in the reactivity was studied. Method: Electrical field stimulation‐evoked contractile response of the juvenile rat tail artery segment under isometric conditions was recorded. 0.1 μm melatonin was administered after the change in the response produced both spontaneously and by acidification (pH 6.6) or alkalinization (pH 7.8) of the solution. Results: During the course of experiment, the contraction force continuously declined, being reduced by 12 ± 5, 24 ± 7 and 32 ± 6% at 20, 70, and 170 min after beginning of experiment, respectively. Melatonin applied at these time points increased the contraction by 20 ± 5, 41 ± 10, and 48 ± 8%, respectively, relative to control. This increase in potentiating effect of melatonin during the course of experiment was not because of sensitization of the segment to the hormone. Acidosis‐induced considerable decline in neurogenic contraction was counteracted by melatonin, while after alkalosis‐induced augmentation in the contraction the hormone was not effective. Melatonin increased the artery response to 0.1 μm noradrenaline. Conclusion: These data suggest that melatonin can restore an attenuated neurogenic reactivity of the juvenile rat tail artery. The effect is more pronounced with further decrease in reactivity and might be due to a change in sensitivity of the post‐junctional membrane to noradrenaline.     

角膜损伤后神经再生的实验研究

应用神经组织化学技术观察了兔角膜NA能神经及AchE阳性神经在角膜损伤后的再生,证实术后1月,两种神经均有再生轴突进入植片;术后3月可见交界区和植床内神经密度明显增加;同时,对术后两种神经再生的功能意义进行了讨论。     

老年大鼠脑内肾上腺素能神经递质系统的变化

本文从下丘脑、大脑皮层、海马等脑区去甲肾上腺素(NA)的含量,其合成酶与降解酶的活性、NA受体数目等多环节的测定来分析肾上腺素能神经递质系统在老化脑中的变化。实验结果表明衰老过程下丘脑、大脑皮层内NA合成酶活性没变化,NA含量明显增高,下丘脑内α_1受体数目显著减少。上述结果提示这些脑区肾上腺素能神经的活动有可能减弱。同时,海马内单胺氧化酶B(MAO B)活性明显增加,说明海马神经元外组织有增生的可能。泰文并讨论了这些变化与老年记忆、行为与神经内分泌等脑功能衰退的关系。     

Pharmacological characterization of the receptor mediating the adrenergic inhibition of responses to substance P in the cingulate cortex

The excitatory responses of neurones in the anterior cingulate cortex of the rat to iontophoretically applied substance P (SP) are reduced by noradrenaline (NA) applied iontophoretically or released from noradrenergic pathways. In order to determine the receptor involved in this inhibitory effect we have studied the effects of a number of receptor-specific adrenergic agonists and antagonists on responses of cingulate neurones to SP in rats anaesthetized with chloral hydrate. Low iontophoretic currents (0-15 nA) of NA, adrenaline and the beta-agonist, clenbuterol, all strongly reduced responses to SP. Isoprenaline was also effective but less consistently so, although problems were experienced with its iontophoretic release from micropipettes. The alpha 1-agonists, phenylephrine and methoxamine were also able to reduce responses to SP. However, this reduction required higher iontophoretic currents (15-60 nA) and was associated with depressant effects on baseline firing rate. The alpha 2-agonist clonidine was only weakly active at high currents and this too was associated with depression of baseline firing. Similar weak effects were noted with dopamine. The inhibitory effects of NA on SP responses were convincingly blocked or reversed by the beta-antagonist, practolol, but not by the alpha 1-antagonist, prazosin. The reduction of SP responses by phenylephrine was also blocked by practolol but unaffected by prazosin. Finally, reduction of SP excitations by activation of the coeruleocortical pathway was also blocked by practolol applied iontophoretically to the cortical cells. These results are consistent with the hypothesis that the effect of NA on SP responsiveness in the cingulate cortex is mediated by beta-adrenoreceptors.     

THE CAIMA SYSTEM

CAIMA is the abbreviation of Computer-Assisted Instant Monitoring drug Administration. CAIMA works on the principle of closed-loop negative feedback. Special programs have been designed to meet the needs of: a) Patients' safety, b) Response level desired, c) Output necessary for actuating the injecting pump. The pump forces the drug solution to enter the body with high precision. The author shows 8-year experience of using CAIMA system in laboratory and in hospital operating rooms. Experimental studies revealed that: CAIMA system attenuates the overshots and undershots usually present in reaction to drug administration, thus saves the drug and thereby causes less side-efiffeets, while the recovery is also much shortened. CAIMA system provides a greater tolerance to extra-stimuli and preserves the body original reactive sensitivity to drug. The homeostasis in animals is better kept with CAIMA than without. Clinically, the arbitrary hypotension during brain surgery with sodium nitroprusside and the control of muscle relaxation in general surgery with muscle relaxants have been successful using CAIMA system.     

米利酮对豚鼠心乳头肌及主动脉条的作用

米利酮是非洋地黄，非儿茶酚胺类强心药，具有明显的正性肌力和扩血管作用。国外用于治疗难治性心衰及洋地黄中毒的心衰病人。本文用豚鼠乳头肌及主动脉条进行实验，结果表明合成与进口米利酮的正性肌力作用效价相同，对抗去甲肾上腺素缩血管的作用也等同。     

Plasma concentrations of prolactin, noradrenaline, vasopressin and oxytocin during and after a prolonged epileptic seizure

The time course and extent of changes in plasma prolactin, noradrenaline, vasopressin and oxytocin levels is reported following serial observations of a prolonged epileptic seizure arising in the temporal lobe, recorded by video-EEG-telemetry, in which the epileptic activity evolved from a simple partial to complex partial to secondarily generalised attack. The prolactin levels were markedly elevated during the phase of the simple partial seizure, at a time when consciousness was preserved, when motor activity was minimal and when EEG activity was highly localised. The hormonal levels continued to rise during the subsequent seizure evolution, suggesting that the duration (or intensity) of the seizure is an important, perhaps the most important, factor determining the degree of prolactin release during limbic seizures. Indeed, the prolactin elevation in this case (26 times the baseline level) is higher than any previously recorded, reflecting the unusual duration and intensity of this seizure. We did not observe the phenomenon of "exhaustion" of prolactin release and levels peaked after 49 min, and were high for over 2 h after the onset of the seizure, and after the convulsion had ceased. The concentrations of vasopressin, oxytocin and noradrenaline remained low during the aura, but rapidly increased during the phase of generalisation. The oxytocin and noradrenaline levels peaked during the phase of generalised convulsion, but the vasopressin levels peaked well into the post ictal phase, and remained high for several hours. The differing patterns of hormone release are likely to be related to the different anatomical sites of the hypothalamic perikarya, the relative importance of excitatory and inhibitory hypophysiotrophic agents in the release of anterior pituitary hormones and the localised release of neuromodulatory agents.     

Automated standardized pupillometry with optical method for purposes of clinical practice and research

The aim of the current study was the introduction and standardization of two experimental conditions for dynamic pupillometry. Pupillometry is a method that can provide valuable data concerning the functioning of the autonomous nervous system. The system for recording the pupil reaction was developed in the Laboratory of Clinical Neurophysiology of the 1st Department of Neurology of Aristotle University of Thessaloniki, in co‐operation with the Laboratory of Fluid Mechanics of the Aristotle University of Thessaloniki. This system is fully automated. It includes an infra‐red video camera, which has the capacity to record in complete darkness, and an SLE (clinical photic stimulator) lamp. A software application automatically performed all the procedures. During the first experiment, one flash was administered. During the second experiment, a series of 25 flashes (1 Hz frequency) was administered. Fifty physically and mentally healthy subjects aged 23–48 years took part in the study. Means, standard deviations and ranges for all variables characterizing normal subjects during both experimental conditions are reported. Test/re‐test results and comparisons of the two eyes are also reported. The combined use of these two experimental conditions in dynamic pupillometry may be a very useful tool in medical research. There are already reports on the usefulness of pupillometry in the research of various diseases, including depression and Alzheimer’s disease. It is expected that it will also be a valuable research tool in the study of diabetes, alcoholism, myasthenia gravis, cancer, multiple sclerosis, etc.     

Extracellular adenosine,formed during low level NMDA receptor activation,provides an inhibitory threshold against further NMDA receptor-midiated neurotransmission in the cortex

In the cortex only a few of the available NMDA receptors must be activated to evoke maximal release of adenosine. In fact, maximal adenosine release occurs at 30 μM NMDA, a concentration at which noradrenaline release is only 20% maximal. NMDA-evoked noradrenaline release appears to require the generation of propagated action potentials, while adenosine release does not. Noncompetitive block of NMDA-evoked release of adenosine, but not noradrenaline, can be overcome by increasing NMDA concentrations. The above findings are consistent with the possibility that there are spare receptors for NMDA-evoked adenosine release, but not for nor-adrenaline release. These spare receptors are not due to elevated levels of glycine in the vicinity of those NMDA receptors mediating adenosine release. Functionally, it appears that low level NMDA receptor activation provides a purinergic inhibitory threshold against higher level NMDA receptor mediated processes. This could provide inhibitory tone and selectivity for critical functions, such as learning, memory, and synaptic plasticity in the cortex. © 1993 Wiley-Liss, Inc.