Stimulus-evoked release of tritiated monoamines from rat periaqueductal gray slices in vitro and its receptor-mediated modulation

Summary The periaqueductal gray is a brain region of considerable interest. It is innervated by monoamine-containing neurons as well as by a variety of peptidergic fiber systems, and it participates in the regulation of various functions. Virtually nothing is known about monoamine release in the periaqueductal gray and its receptor-mediated modulation. We therefore studied the release of radioactivity from periaqueductal gray slices preloaded with tritriated monoamines, using an in vitro superfusion method.The release of radioactivity from superfused periaqueductal gray slices after preloading of the tissue with [³H]noradrenaline increased upon electrical stimulation in a frequency-dependent manner. The stimulus-evoked release of radioactivity was Ca²⁺-dependent. Clonidine reduced and yohimbine enhanced the release. The inhibition curve for the effect of clonidine was shifted to the right in the presence of 10^–6 M yohimbine. While phenylephrine, isoprenaline, SK&F 38393, quinpirole, carbachol, [Arg⁸]vasopressin, -MSH and ACTH-(1-24), at a concentration of 10^–6 M, did not influence the electrically evoked release of radioactivity, [Leu⁵]enkephalin reduced it. The selective -opioid receptor agonists [d-Ala²,NMePhe⁴,Gly-ol⁵]enkephalin and [d-Arg²,Lys⁴]-dermorphin-(1–4)-amide reduced the release of radioactivity, whereas the selective opioid receptor agonist [d-Pen²,d-Pen⁵]enkephalin and the selective K opioid receptor agonist U-69593 had no effect. In the presence of naloxone, which by itself had no effect on the release of radioactivity, the effect of [d-Arg²,Lys⁴]dermorphin-(1–4)-amide was abolished. These results show that the release of noradrenaline from periaqueductal gray slices is via a Ca²⁺-dependent. exocytotic process, and that it is modulated through ₂-adrenoceptors as well as via -opioid receptors. Though the overflow of radioactivity from slices preloaded with [3H]dopamine in the presence of desipramine was measurable, there are reasons to assume that we are dealing here with the release of tritiated catecholamines from a population of nerve endings consisting of noradrenergic and dopaminergic terminals.The release of radioactivity from periaqueductal gray slices preloaded with [³H]5-hydroxytryptamine upon elevation of the K⁺ concentration in the superfusion medium was much more pronounced than that induced by electrical stimulation. The K⁺-evoked release of radioactivity was almost completely abolished in the absence of Cat²⁺; showing that the release is via a Ca²⁺-dependent process. 5-Hydrotryptamine reduced the K⁺-evoked release of radioactivity in a concentration-dependent manner.Some of these data were presented at the XIth International Congress of Pharmacology, 1–6 July 1990, Amsterdam, The Netherlands (Eur J Pharmacol 183:408) Send offprint requests to D. H. G. Versteeg at the above address     

孕育铸铁中石墨分布与力学性能的定量关系

本文利用图象分析技术,定量分析灰铸铁孕育处理后石墨相的分布情况。发现石墨相体积分率与灰铸铁综合性能有较为一致的关系,确定了孕育处理时孕育剂应用的最佳方案。     

Antinociception produced by mu opioid receptor activation in the amygdala is partly dependent on activation of mu opioid and neurotensin receptors in the ventral periaqueductal gray

Exposure to stressful or fear-inducing environmental stimuli activates descending antinociceptive systems resulting in a decreased pain response to peripheral noxious stimuli. Stimulating mu opioid receptors in the basolateral nucleus of the amygdala (BLA) in anesthetized rats produces antinociception that is similar to environmentally induced antinociception in awake rats. Recent evidence suggests that both forms of antinociception are mediated via projections from the amygdala to the ventral periaqueductal gray (PAG). In the present study, we examined the types of neurochemicals released in the ventral PAG that may be important in the expression of antinociception produced by amygdala stimulation in anesthetized rats. Microinjection of a mu opioid receptor agonist into the BLA resulted in a time dependent increase in tail flick latency that was attenuated by preadministration of a mu opioid receptor or a neurotensin receptor antagonist into the ventral PAG. Microinjection of a delta(2) opioid receptor antagonist or an NMDA receptor antagonist into the ventral PAG was ineffective. These findings suggest that amygdala stimulation produces antinociception that is mediated in part by opioid and neurotensin release within the ventral PAG.     

Phenytoin administration reveals a differential role of pontine reticular formation and periaqueductal gray neurons in generation of the convulsive behaviors of audiogenic seizures

The ventrolateral periaqueductal gray (PAG) and pontine reticular formation (PRF) are implicated in the neuronal network for audiogenic seizures (AGS). The AGS of genetically epilepsy-prone rats (GEPR-9s) culminate in tonic hindlimb extension (TE), and elevated acoustically evoked neuronal firing and burst firing, immediately preceding TE, have been observed in PAG and PRF. This study examined changes in PAG and PRF neuronal firing and behavior in GEPR-9s, following phenytoin administration. Recordings involved 16 PAG and nine PRF neurons in GEPR-9s. Phenytoin in doses (mean, 6. 3 mg/kg) that suppressed TE selectively did not consistently alter PAG neuronal firing. However, these doses of phenytoin resulted in significant (51.6% of control) suppression of PRF neuronal firing. Doses of phenytoin (mean, 8.3 mg/kg), which completely blocked AGS, significantly reduced PAG neuronal firing (64.6% of control), and more greatly suppressed PRF firing (25.8% of control). These results are consistent with a critical role for PRF neurons in generation of TE not evident for PAG. The suppression of PAG and PRF neuronal firing induced by phenytoin with complete seizure blockade is consistent with vital roles for both structures in the seizure network. The differential effects of phenytoin on structures requisite to the seizure network indicate that this experimental approach may be able to identify the most sensitive therapeutic target for anticonvulsant drugs, which could be critical to pharmacological suppression of specific seizure behaviors manifest in various types of convulsions, potentially including human epilepsy.     

Anatomical substrate for separate processing of ascending and descending visceral information in the nucleus of the solitary tract of the rat

We examined the possible existence of divergent visceral pathways arising from the nucleus of the solitary tract, by co-injecting axonal tracers into the parabrachial nucleus and into the ventrolateral medulla. We found that around 5% of NTS neurons projected to both sites, and that neurons projecting to VLM were larger. This parallel organization allows a differential control of the ascending versus descending visceral pathways at an early stage of processing.     

超声医学图像灰度校正方法的改进

介绍了超声医学图像灰度校正常用方法的基本原理,这些方法主要有灰度级校正、灰度变换及直方图修正。对广泛应用且效果较好的直方图均衡化法作了较详细阐述,并针对其对于局部细节增强不显著及不具交互特征等缺点提出了改进方法,并将几种灰度校正方法级联起来对超声图像进行处理,实现了有选择地增强某个灰度值范围对比度的功能,增强了超声诊断图像的实用性。     

我国人口的灰色预测模型研究及其应用

应用GM(1,1)模型,根据1982~1990年我国人口的实际统计数据建立了灰色预测模型,并对我国未来人口进行了预测。     

改良V-Y外眦开大成形术的临床应用

目的：探讨改良V-Y外眦开大成形新术式。方法：将Y形切口线设计在睑缘灰线，板层劈开上下睑，并在切口末端增加两条垂直于睑缘的辅助切口线，切开睑板及睑结膜；部分或完全切断外眦韧带，充分分离使外眦呈“游离状态”。在无张或微张力的情况下外移外眦。结果：102例外眦开大成形术99例达到预期效果，开大外眦达1．5～5mm。结论：改良V-Y外眦开大成形术相比传统手术，保留了外眦外形结构，术后外眦无变形，远期回缩轻微，是目前比较理想的合乎美学原理的外眦开大成形术式。     

Frontal and subcortical contribution to visual hallucinations in dementia with Lewy bodies and Parkinson’s disease

Objectives: Visual hallucinations (VH) are common in Lewy body disease (LBD), and have been associated with cognitive and structural brain alterations. Evidence so far concerns mainly Parkinson’s disease (PD), but little is known about symptom-specific pathophysiological mechanisms across the LBD spectrum, especially related to the presence of dementia. The aim of the present pilot study was to investigate the neuroanatomical, and neuropsychological characteristics related to VH in two forms of LBD, namely dementia with Lewy bodies (DLB) and PD without dementia.

Methods: Whole brain voxel-based morphometry (VBM) analyses on 3D MRI acquired structural brain scans, and neuropsychological testing were performed on 28 clinically diagnosed DLB (11 with VH, 17 NVH), and 24 PD (9 with VH, and 15 NVH) patients. In order to assess differences in gray matter (GM) regional volumes, and cognitive performance, hallucinating patients for each group were compared with corresponding non-hallucinating ones.

Results: DLB patients with VH presented significantly worse visual attention deficits compared to those without, which persisted even when controlling for visual perception. Whole brain VBM analysis revealed decreased GM volume in DLB with VH in the right superior and medial frontal gyri, putamen, caudate nucleus and insula. Subcortical regional volumes were also significantly associated with visual attention performance. Hallucinating PD patients, instead, presented more severe executive dysfunction, but VBM showed no volumetric differences between the two PD subgroups. Post hoc region of interest analyses revealed striatal GM loss in PD with VH.

Conclusion: Frontal and striatal GM atrophy may contribute to the emergence of VH in DLB, which may be fostered by the more severe attention deficits. Striatal GM loss and executive dysfunction, instead, appeared to underlie VH in PD without dementia.