Tyrosine hydroxylase activity and dopamine turnover of rainbow trout (Oncorhynchus mykiss) brain: the special status of the hypothalamus

The dynamics of catecholamine (CA)-synthesis enzymes have been poorly studied in fish. Tyrosine hydroxylase (TH), the rate-limiting enzyme of CA synthesis has been only studied inin vitro conditions. In the present report thein vivo CA synthesis and the CA metabolism were studied in different regions of the forebrain of the rainbow trout. Levels of norepinephrine (NE), dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC) and the rate of accumulation of 3,4-dihydroxyphenylalanine (DOPA) were determined by HPLC following a treatment with hydroxybenzylhydrazine (NSD), a potential inhibitor of DOPA decarboxylase. Kinetics of the accumulation of DOPA and of the decline of DOPAC were in agreement with those found in rat, evidencing that the accumulation of DOPA following NSD can be used in trout to quantify thein vivo enzymatic activity of tyrosine hydroxylase. Experiments using treatment with NSD or with methyl-p-tyrosine reached a same conclusion: the DA neuronal activity in trout is much higher than NE neuronal activity. However, the hypothalamus had high DA levelsvs. lowin vitro andin vivo TH activities and exhibited a low CA turnover.     

Catecholamine synthesis in the rainbow trout (Oncorhynchus mykiss) brain: modulation of tyrosine hydroxylase activity

Levels of catecholamines and tyrosine hydroxylase (TH) activity were measured in brain homogenates from female rainbow trout. In triploid fish or in diploid fish in ovarian recrudescence, the patterns of catecholamine content expressed as a function of in vitro TH activity vary in different areas of the brain. K_m for the pterin cofactor is lower in the telencephalon than in the hypothalamus. Dopamine (DA) and 2-hydroxyestradiol (20HE₂) inhibit TH activity (by competitive and non-competitive interaction respectively). The K₁ for DA were different in the telencephalon and the hypothalamus and this could explain the different patterns of catecholamine levels and TH activity for these two structures. 20HE₂ inhibits TH activity in vitro; a catechol moiety is required since estradiol (E₂) is notinhibitory. However, the exact mechanism of inhibition remains unclear. The rapid effect of 20HE₂ cannot explain the previously reported activation of catecholamine synthesis by E₂ in vivo.

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Reśumé Les taux de catécholamines cérébrales et l'activité in vitro de la tyrosine hydroxylase (TH) ont été déterminés chez la truite arc en ciel femelle. Chez des animaux triploides ou diploides en recrudescence ovarienne, les taux de catécholamines sont corrélés différemment à l'activité TH selon la structure cérébrale considérée. Le télencéphale présente un K_m apparent pour la ptérine plus faible que l'hypothalamus. La dopamine (DA) et le 2-hydroxyestradiol (20HE₂) inhibent l'activité de la TH selon des mécanismes respectivement compétitifs Les différents K₁ pour la DA obtenus au niveau du télencéphale et de l'hypothalamus pourraient expliquer les différentes relations entre taux de catécholamines et activité TH obtenues pour ces deux structures. Le 20HE₂ inhibe également l'activité TH in vitro: la présence d'un radical catéchol s'avère nécessaire (l'oestradiol (E₂) n'est pas actif par lui-même), mais le mécanisme de l'inhibition reste à déterminer. Les effets rapides du 20HE₂ ne peuvent expliquer l'activation de la synthèse catécholaminergique par l'E₂ in vivo démontrée antérieurement.

     

斑马鱼端脑的微细形态与结构

为了深入了解斑马鱼端脑的微细形态和超微结构,采用光镜和电镜技术对斑马鱼端脑进行观察研究。斑马鱼端脑由左、右嗅球和左、右大脑半球构成。嗅球前方有一对嗅神经,后端伸出嗅茎与大脑半球联系。光镜下,嗅球组织结构从外向内依次为上皮层、神经纤维层、小细胞层和内部细胞层。大脑半球外部覆盖很薄的大脑皮,基部为纹状体,两者之间的腔隙为公共脑室。纹状体由神经核团和神经纤维构成。神经核团分布于纹状体周缘,主要有连前核、背嗅核、侧嗅核、视前核和脚内核等。神经纤维包括横行的前连合,纵行和斜行的中央嗅束和侧嗅束。电镜下,嗅球分层明显,可观察到僧帽细胞、神经胶质细胞和众多突触。大脑半球中可见神经胶质细胞、突触以及血脑屏障系统等。斑马鱼端脑形态结构与大多数硬骨鱼相似,但有个别核团存在差异。实验结果可为斑马鱼神经生物学模型的建立与应用提供有效的理论基础。     

Studies on Thysanura. I. The Water Economy of Machiloides Delanyi Wygodzinsky and Ctenolepisma Longicaudata Escherich

Forebrain extirpations from Hemihaplochromis philander (Pisces: Cichlidae) resulted in a decrease of aggressive (territorial), courtship, and spontaneous behaviour. The stimulus-response latency was found to be increased by the extirpations. Forebrainless males were unable to distinguish between male and female conspecifics on a visual basis. Abnormal responses to certain stimuli occasionally resulted in accidents suggesting a failure of neural feedback mechanisms.

It was suggested that the teleost forebrain houses a primitive limbic system the main functions of which would be general arousal and the selection of appropriate responses to the incoming external and endogenous (motivational) stimuli     

鸡端脑突触素的表达与发育研究

应用免疫组织化学印法,研究了突触素在70,2l0,395日龄鸡端脑中的表达。研究表明：突触素免疫反应产物主要以颗粒状、点状形式存在,少部分区域出现阳性神经元。突触素免疫反应产物密度在70,2lO,395日龄表现出2种变化趋势：①副高纹状体、高纹状体、新纹状体、背海马、海马背外侧部：升高→降低;旧纹状体膨大、原始旧纹状体、外纹状体、古纹状体、基底核、旁海马、海马背内侧部：保持不变。结果揭示：副高纹状体、高纹状体、新纹状体、背海马、海马背外侧部神经元可能受生殖激素的调节,从而影响突触数量和神经元功能;副高纹状体、高纹状体、新纹状体、背海马、海马背外侧部可能与生殖有关的结构存在联系,并对其发挥一定的高级调节作用。     

生长相关蛋白免疫反应神经纤维在20胚龄鸡端脑中的分布

为了给家禽发育神经解剖学积累资料，应用免疫组化 Ａ Ｂ Ｃ 法，对 ２０ 胚龄鸡端脑进行了生长相关蛋白（ Ｇ Ａ Ｐ４３）免疫反应神经纤维分布的研究。结果表明，在端脑新纹状体中含有大量较细的阳性纤维，阳性纤维多集中在新纹状体靠近背髓板区域，纤维有分支且交织成网。部分阳性纤维穿过背髓板向腹下方移行，伸向旧纹状体扩大部。在旧纹状体扩大部，有呈背腹方向排列的短阳性纤维束，数量较多，向尾侧伸向初级旧纹状体。在初级旧纹状体中，阳性纤维束以腹内侧方向排列为主，并有少量细的纤维分支互相交织，向腹内侧移行，逐渐聚集成纹体丘脑束。纹体丘脑束参与形成额丘脑束，伸向丘脑。     

The distribution of calbindinD‐28k and parvalbumin immunoreactive neurons in the somatosensory area of the pigeon pallium

GABAergic interneurons regulate the degree of glutamatergic excitation and output of projection neurons. In this study, we investigated the distribution of calbindinD‐28k (CB) and parvalbumin (PV) in the somatosensory area of the pigeon pallium using immunohistochemical method. Our results show that anatomical structures of the somatosensory area of the pigeon pallium consisted of several subdivisions including the hyperpallium, intercalated hyperpallium, mesopallium, nidopallium and basorostralis. Neuronal density was significantly higher in the intercalated hyperpallium and basorostralis than that in the other subdivisions. The density of the CB immunoreactive neurons was generally similar in all the subdivisions; however, the density of PV immunoreactive neurons was particularly prominent in the basorostralis compared with that in the other subdivisions. In addition, the mean proportion of PV immunoreactive neurons to total neurons was higher than that in the CB immunoreactive neurons in all the subdivisions. In brief, our present study shows that PV immunoreactive neurons in the somatosensory area of the pigeon pallium were significantly abundant compared with CB immunoreactive neurons. This finding needs more studies regarding CB‐ and PV‐related functions in the somatosensory area of the avian pallium.