The dorsal groove and associated structures on the head of the sucking loach, Gyrinocheilus aymonieri (Cypriniformes)

A prominent transverse groove is present on the snout of the adult sucking loach, Gyrinocheilus aymonieri . It is absent in juveniles. The groove is formed by fibrous thickenings of the dermis that create skin folds at its anterior and posterior margins. It accommodates movement of the joint between the maxillae and the neurocranium. The anterior fibrous thickening also provides anchorage for fibrous strands that partition dermal mucochondroid in the upper lip of the oral sucker into distinct segments. This structure forms a buffer that protects the delicate premaxillary bones when fish probe the substrate for food.     

Characteristics of store-operated calcium channels activated by depletion of the endoplasmic reticulum ryanodine-sensitive calcium stores in rat dorsal root ganglion neurons

In neurons of the rat dorsal root ganglia (DRG), using a patch-clamp technique in the whole-cell configuration, we studied the characteristics of calcium channels activated by depletion of the ryanodine-sensitive calcium stores of the endoplasmic reticulum. Current-voltage (I-V) relationships of these store-operated calcium channels were obtained by subtraction of the integral I-V characteristics after application of caffeine from the integral I-V characteristics of calcium channels in the control. Currents through store-operated calcium channels could be induced by application of a series of hyperpolarization current pulses to the cell under conditions of replacement of a calcium-free solution containing caffeine by a caffeine-free solution containing 2 mM Ca²⁺. In this case, the following two main conditions were abserved: Voltage-operated calcium channels were inactivated, while a gradient of the electrochemical potential for calcium ions was increased, which made easier passing of these currents through store-operated calcium channels. Therefore, we found that in DRG neurons, despite the presence of great numbers of both voltage-operated and receptor-dependent calcium channels, one more mechanism underlying the entry of calcium through store-operated channels does exist. Neirofiziologiya/Neurophysiology, Vol. 39, No. 3, pp. 195–200, May–June, 2007.     

Modulation of electrically evoked serotonin release in cultured rat raphe neurons

Electrically evoked release of serotonin (5-HT) and its modulation via 5-HT autoreceptors and alpha(2)-heteroreceptors was studied in primary cell cultures prepared from the embryonic (ED 15) rat mesencephalic brain region comprising the raphe nuclei. Cultures were grown for up to 3 weeks on circular glass coverslips. They developed a dense network of non-neuronal and neuronal cells, some of which were positive for tryptophan hydroxylase. To measure 5-HT release, the cultures were pre-incubated with [(3)H]5-HT (in the presence of the selective noradrenaline reuptake inhibitor oxaprotiline [1 micromol/L]), superfused with modified Krebs-Henseleit medium containing 6-nitroqipazine [1 micromol/L] and electrically stimulated using two conditions. Condition A: 360 pulses, 3 Hz, 0.5 ms, 90 mA, or condition B: 4 pulses 100 Hz, 0.5 ms, 90 mA (a condition which diminishes interactions with endogenously released transmitters during ongoing stimulation). After only 1 week in culture, the electrically evoked overflow of [(3)H] was Ca(2+) dependent and tetrodotoxin sensitive, suggesting an action-potential-induced exocytotic release of 5-HT. Using stimulation condition A in cultures grown for 2 weeks, both basal and evoked 5-HT release were strongly enhanced by methiotepine (1 micromol/L) but unaffected by the 5-HT(1B) autoreceptor agonist CP-93, 129 (1 micromol/L) and the alpha(2)-adrenoceptor agonist UK-14, 304 (1 micromol/L). Conversely, using stimulation condition B, not only CP-93, 129 (IC(50) 8.1 +/- 1.4 nmol/L) and UK-14, 304 (IC(50) 14.9 +/- 1.6 nmol/L) had inhibitory effects on cells grown for 2 weeks, but also the 5-HT(1A) agonist 8-hydroxy-2-(di-n-propylamino)tetralin. In conclusion, we describe for the first time electrically evoked release of 5-HT from primary cultures of fetal raphe cells and its modulation via 5-HT(1B) and 5-HT(1A) auto- and alpha(2)-heteroreceptors. Such cultured raphe cells may represent a suitable model to study expression and development of presynaptic receptors on serotonergic neurons in-vitro.     

Agonist-mediated regulation of presynaptic receptor function during development of rat septal neurons in culture

Presynaptic receptors modulating the release of acetylcholine (ACh) were studied in fetal septal neurons cultured in a growth medium to which various drugs were added from day 3 in vitro (DIV 3) to DIV 14. The influence of these drugs on the function of the presynaptic muscarinic (M-) autoreceptor was determined at DIV 14 by measuring the inhibitory effect of the M-agonist oxotremorine on the electrically-evoked release of [(3)H]ACh from cultures pre-incubated with [(3)H]choline. The presence of the M-agonists oxotremorine (100 micromol/L) or carbachol (100 micromol/L) from DIV 3 to DIV 14, or from DIV 13 to DIV 14, abolished M-autoreceptor function at DIV 14, whereas the presence of the M-antagonist atropine (10 micromol/L from DIV 3 to DIV 14) during growth left M-autoreceptor function unaltered. Inhibition of ACh esterase by donepezil (1 micromol/L from DIV 3 to DIV 14) weakly decreased M-autoreceptor function at DIV 14; inhibition of neuronal firing by 0.1 tetrodotoxin (0.1 micromol/L from DIV 3 to DIV 14) did not tend to affect M-autoreceptor function at DIV 14. Co-cultivation of fetal septal and raphe neurons for 2 weeks yielded cell cultures containing both vesicular ACh transporter- and tryptophan hydroxylase-immunopositive cells. From these cultures, the release of both [(3)H]ACh and [(3)H]5-HT could be induced by electrical field stimulation. In co-cultured neurons versus septal-only ones the inhibitory effect of oxotremorine on the evoked release of [(3)H]ACh appeared almost normal, whereas that of the selective 5-HT(1B) agonist 3-(1,2,5,6-tetrahydropyrid-4-yl)pyrrollo[3,2-b]pyrid-5-one (CP-93,129) was completely abolished. The effects of CP-93,129 were also absent on DIV 14 in septal mono-cultures grown in the presence of CP-93,129 (10 micromol/L) from DIV 3 to DIV 14. It is therefore concluded that the regulation of presynaptic receptor function strongly depends on the concentrations of endogenous transmitters in the neuronal environment.     

Alterations in lipid homeostasis of mouse dorsal root ganglia induced by apolipoprotein E deficiency: a shotgun lipidomics study

One of the fundamental goals of lipidomics research is to identify the linkage of an individual gene with a given lipidome, thereby revealing the role of that gene in lipid metabolism, transport, and homeostasis. In this study, we have identified four apolipoprotein E (apoE)-induced alterations in the lipidome of mouse dorsal root ganglia (DRG) through utilizing the technology of shotgun lipidomics. First, apoE mediates sulfatide mass content in mouse DRG, which is comparable to its role in the CNS. Second, apoE contributes to galactosylceramide and ceramide homeostasis in mouse DRG. Third, apoE significantly modulates cholesterol levels in mouse DRG. The latter two functions of apoE are distinct from those in the CNS. Finally, mice null for apoE have dramatically less triacylglycerol mass content in DRG which are opposite to the effects observed in the peripheral organs and vascular system. Collectively, this study identifies the specific alterations in the DRG lipidome induced by apoE knockout and suggests the potential roles of apoE in lipid transport and homeostasis in a tissue specific manner, thereby providing insights into the biochemical mechanisms underlying the functions of apoE in the PNS.     

NO-cGMP mediated galanin expression in NGF-deprived or axotomized sensory neurons

Leukaemia inhibitory factor (LIF) and nerve growth factor (NGF) are well characterized regulators of galanin expression. However, LIF knockout mice containing the rat galanin 5' proximal promoter fragment (- 2546 to + 15 bp) driving luciferase responded to axotomy in the same way as control mice. Also, LIF had no effect on reporter gene expression in vitro, neither in the presence or absence of NGF, suggesting that other factors mediate an axotomy response from the galanin promoter. We then addressed the role of nitric oxide (NO) using NGF-deprived rat dorsal root ganglion (DRG) neuron cultures infected with viral vectors containing the above-mentioned construct, and also studied endogenous galanin expression in axotomized DRG in vivo. Blocking endogenous NO in NGF-deprived DRG cultures suppressed galanin promoter activity. Consistent with this, axotomized/NGF-deprived DRG neurons expressed high levels of neuronal NO synthase (nNOS) and galanin. Further, using pharmacological NOS blockers, or adenoviral vectors expressing dominant-negative either for nNOS or soluble guanylate cyclase in vivo and in vitro, we show that the NO-cGMP pathway induces endogenous galanin in DRG neurons. We propose that both LIF and NO, acting at different promoter regions, are important for the up-regulation of galanin, and for DRG neuron survival and regeneration after axotomy.     

The cross channel activities of spider neurotoxin huwentoxin-I on rat dorsal root ganglion neurons

In this paper, we investigated the action of huwentoxin-I (HWTX-I) purified from the venom of the Chinese bird spider Ornithoctonus huwena on Ca(2+), Na(+) channels of adult rat dorsal root ganglion (DRG) neurons. The results showed that huwentoxin-I could reduce the peak currents of N-type Ca(2+) channels (IC(50) approximately 100 nM) and TTX-S Na(+) channels (IC(50) approximately 55 nM), whereas no effect was detected on TTX-R Na(+) channels. The comparative studies indicated that the selectivity of HWTX-I on Ca(2+) channels was higher that of MVIIA and approximately the same as that of GVIA. HWTX-I is the first discovered toxin with the cross channel activities from the spider O. huwena venom similar to micro O-conotoxins MrVIA and MrVIB.     

毁损大鼠中缝背核内触液神经元对吗啡依赖和戒断的影响

目的:探索脑内远位触液神经元在吗啡依赖和戒断形成过程中的作用。方法:化学性神经元毁损、侧脑室引入霍乱毒素亚单位B与辣根过氧化物酶复合物(CB-HRP)神经示踪、TMB-ST呈色反应,Western blot、nNOS免疫组织化学。结果:毁损大鼠中缝背核内远位触液神经元后,纳洛酮催促的戒断症状明显减弱,戒断症状评分较戒断未毁损组降低约38%(P<0.05);给予溶媒和毁损触液神经元旁侧的大鼠戒断症状与戒断组比较未见明显变化(P>0.05)。毁损组脑片触液神经元密集区局部细胞损坏明显,仅在其毁损区边缘观测到少量CB-HRP阳性细胞。未毁损组CB-HRP标记细胞位置及数量恒定,形态清晰。毁损触液神经元后,脊髓背角nNOS阳性神经元计数及nNOS蛋白表达较戒断未毁损组减少明显(P<0.05),而较正常组和依赖组增加仍显著(P<0.01)。结论:毁损大鼠中缝背核内部分远位触液神经元可减弱吗啡戒断症状和脊髓背角神经元型一氧化氮合酶的表达,提示中缝背核内部分远位触液神经元可能参与了吗啡依赖和戒断的形成,NO介导脑内触液神经元与脊髓水平对吗啡依赖和戒断的调节。     

Effect of Electroacupuncture on Neurotrophin Expression in Cat Spinal Cord after Partial Dorsal Rhizotomy

Neuroplasticity of the spinal cord following electroacupuncture (EA) has been demonstrated although little is known about the possible underlying mechanism. This study evaluated the effect of EA on expression of neurotrophins in the lamina II of the spinal cord, in cats subjected to dorsal rhizotomy. Cats received bilateral removal of L1–L5 and L7–S2 dorsal root ganglia (DRG, L6 DRG spared) and unilateral EA. They were sacrificed 7 days after surgery, and the L6 spinal segment removed and processed by immunohistochemistry and in situ hybridization histochemistry, to demonstrate the expression of neurotrophins. Significantly greater numbers of nerve growth factor (NGF) and neurotrophin-3 (NT-3) positive neurons, brain-derived neurotrophic factor (BDNF) immunoreactive varicosities and NT-3 positive neurons and glial cells were observed in lamina II on the acupunctured (left) side, compared to the non-acupunctured, contralateral side. Greater number of neurons expressing NGF mRNA was also observed on the acupunctured side. No signal for mRNA to BDNF and NT-3 was detected. The above findings demonstrate that EA can increase the expression of endogenous NGF at both the mRNA and protein level, and BDNF and NT-3 at the protein level. It is postulated that EA may promote the plasticity of the spinal cord by inducing increased expression of neurotrophins.