hNa_v1.8mRNA在三叉神经痛患者痛支神经中的表达

目的：观察河脉毒素不敏感型钠通道Navl．8 mRNA在三叉神经痛(trigeminal neuralgia,TN)患者痛支神经中的表达。方法：利用RT—PCR技术，以β—actin为内参照，检测5例原发性TN保守治疗无效患者的痛支神经、2例行舌颌颈联合根治术患者正常耳大神经和肌肉组织中hNavl．8 mRNA的表达。结泉：hNavl．8 mRNA在TN患者痛支神经中有明显表达，而在正常耳大神经及肌肉组织中均无表达。结论：hNavl．8 mRNA在三叉神经痛支中的异常表达可能与TN的发病机制有关。     

河豚毒素分析检测方法研究进展

河豚毒素是非蛋白类海洋神经毒素，其强毒性及在医学、军事学等领域的广泛应用为中外学者所重视。本文对近年来河豚毒素检测方法的进展作一综述。     

Effects of veratridine, tetrodotoxin and other drugs that alter electrical behaviour on secretion of melanocyte-stimulating hormone from melanotrophs of the pituitary pars intermedia

Since melanotrophs are electrically active and exhibit spontaneous Na spikes, a study was made of the effects, on melanotroph secretion, of drugs known to influence electrical properties. The output of melanocyte-stimulating hormone was measured from perifused neurointermediate lobes of mice or melanotrophs dispersed from such lobes of mice or rats. Veratridine (200 microM), which is known to increase Na permeability in a variety of cells, caused a large, although transient, increase in secretion from the melanotrophs that required extracellular Ca2+ and was blocked by the Na-channel blocker tetrodotoxin (1 microM). Tetraethylammonium (10 mM), which blocks K channels and thus prolongs the duration of the action potential in many cells, also stimulated secretion in the melanotrophs in a Ca-dependent manner. This response was not, however, blocked by tetrodotoxin, and is thus not attributable to prolongation of Na spikes in these cells. Moreover, tetrodotoxin did not inhibit basal secretion. The stimulant effect of veratridine on secretion in melanotrophs and its suppression by tetrodotoxin suggests that voltage-dependent Na channels can participate in the regulation of hormone output in these cells of the pituitary pars intermedia. However, the apparent lack of effect of tetrodotoxin on basal secretion suggests that the spontaneous Na spikes previously observed in these cells are not required for promoting the Ca influx which other evidence shows is important for basal secretion.     

Membrane properties of rat locus coeruleus neurones

Intracellular recordings were made from neurones in the locus coeruleus contained within a slice cut from rat pons and maintained in vitro. Most neurones fired action potentials spontaneously at frequencies of between 1 and 5 Hz; this did not arise from spontaneous synaptic input but appeared to result from endogenous properties of the membrane conductances. Under voltage clamp at potentials near threshold for action potential generation (? 55 mV) there was a persistent inward calcium current. This current became less with membrane hyperpolarization and was abolished at about ?70 mV. Two potassium currents were observed. The first had properties similar to that generally described as the “fast” potassium current (I_K,A); it flowed transiently (for about 200 ms) when the membrane potential passed from about ?65 to ?45 mV, and was blocked by 4-aminopyridine. The second was a calcium-activated potassium current (I_K,Ca); it flowed for several seconds following a burst of calcium action potentials. Spontaneous and evoked action potentials had both tetrodotoxin-sensitive and tetrodotoxin-resistant components. The latter was apparently due to calcium entry. The potential changes occurring during the spontaneous firing of locus coeruleus neurones could be reconstructed qualitatively from the ionic conductances observed. The membrane properties of the locus coeruleus neurones were remarkably uniform; however, about 5% of cells impaled within the region of the locus coeruleus were electrophysiologically distinct. These atypical cells had short duration action potentials, did not fire spontaneously and had large spontaneous depolarizing synaptic potentials.     

Electrical behaviour in a line of anterior pituitary cells (GH cells) and the influence of the hypothalamic peptide, thyrotrophin releasing factor

Anterior pituitary cells of the GH line, which secrete prolactin spontaneously, showed spontaneous action potential activity. Thyrotrophin releasing factor, which increases secretion in these cells, caused a prompt increase of action potential frequency. Potassium, another secretagogue, depolarized the cells and sometimes initiated a burst of action potentials at the onset of this effect. The action potentials persisted in tetrodotoxin-containing and Na-free media, but were suppressed by the Ca-channel blocker, methoxyverapamil. Moreover, elevating the extracellular Ca²⁺ concentration increased the amplitude of the action potentials. These action potentials therefore have a prominent Ca component. This endows them with a particular interest since secretory activity of these cells is known to be dependent on extracellular Ca²⁺. Ba²⁺, which can substitute for Ca²⁺ in maintaining secretion, also substituted for Ca²⁺ in the maintenance of the action potentials. In addition, Ba²⁺ prolonged action potentials remarkably: tetraethylammonium was less effective in this regard.The several parallels between known secretory behaviour and electrical phenomena encourage the view that analysis of electrical activity in anterior pituitary cells may provide useful clues to events involved in stimulus-secretion coupling and in the secretory control exerted by the brain.     

Different ion channel mechanisms between low concentrations of capsaicin and high concentrations of capsaicin and nicotine regarding peptide release from pulmonary afferents

Vagal nerve stimulation (1 Hz for 1 min), capsaicin (10^-8 M and 10^-6 M), resiniferatoxin (3 × 10^-10 M) and nicotine (10^-4 M) evoked a non-cholinergic bronchoconstriction in the isolated perfused guinea-pig lung preparation. Simultaneously there was an increase in the perfusate levels of calcitonin gene-related peptide-like immunoreactivity, suggesting release from sensory nerves. Both the bronchoconstriction and peptide release evoked by a low concentration of capsaicin (10^-8 M) and that evoked by nerve stimulation were depressed by tetrodotoxin, suggesting involvement of Na⁺ channel dependent depolarization. Since the effects of capsaicin (10^-8 M) and vagal nerve stimulation were inhibited by ω-conotoxin but not influenced by nifedipine, the Ca²⁺-channel involved is probably of N-type. Furthermore, the capsaicin analogue resiniferatoxin also evoked ω-conotoxin sensitive peptide release and bronchoconstriction. At the higher capsaicin concentration (10^-6 M), the functional response was only slightly inhibited by wconotoxin or tetrodotoxin indicating that capsaicin at this concentration evoked peptide release and functional effects through other mechanisms, probably involving Ca²⁺ fluxes in the non-selective cation channel associated with the proposed capsaicin receptor. The nicotine (10^-4 M) evoked peptide release and bronchoconstriction were only marginally influenced by ω-conotoxin or tetrodotoxin. It is concluded that the ion-channel mechanisms underlying the peptide releasing properties of antidromic nerve stimulation and low concentrations of capsaicin are similar and depend on action potential propagation, whereas capsaicin in high, toxic concentration and nicotine mainly act via receptor operated channels.     

Release of endogenous 5-hydroxytryptamine from the neural and the intermediate lobe of the rat pituitary gland evoked by electrical stimulation of the pituitary stalk

A calcium-dependent release of 5-hydroxytryptamine from the neural and intermediate lobe of the rat pituitary gland has been demonstrated following electrical stimulation of the pituitary stalk with stimulation parameters thought to evoke propagated action potentials. The 5-hydroxytryptamine release from the intermediate lobe was double that from the neural lobe. The mass of the intermediate lobe of the rat is about 80% of that of the neural lobe [Holzbauer, Racké, Mann, Cooper, Cohen, Krause and Sharman (1984) J. Neural Transm. 59, 91-104]. The relatively high overflow of 5-hydroxytryptamine from the intermediate lobe agrees with immunohistochemical studies in which a larger number of 5-hydroxytryptamine fibres were seen in the intermediate lobe than in the neural lobe. The present results have demonstrated that the rat hypophysis contains neuronal 5-hydroxytryptamine. They also suggest that this amine may act as a neurotransmitter substance in the neural and intermediate lobe.     

Effects of benactyzine on action potentials and contractile force of guinea pig papillary muscles

ＩＮＴＲＯＤＵＣＴＩＯＮＢｅｎａｃｔｙｚｉｎｅｉｓａｓｙｎｔｈｅｔｉｃｂｌｏｃｋｅｒｏｆＭ ｒｅｃｅｐｔｏｒｐｏｓ ｓｅｓｓｉｎｇｓｍｏｏｔｈｍｕｓｃｌｅｒｅｌａｘａｎｔｐｒｏｐｅｒｔｉｅｓａｎｄｑｕｉｎｉｄｉｎｅ ｌｉｋｅａｃｔｉｏｎｏｎｈｅａｒｔ[1] .Ｂｅｎａｃｔｙｚｉｎｅｉｓｅｆｆｅｃｔｉｖｅｉｎｒｅｓｔｏｒ ｉｎｇｃｉｒｃｕｌａｔｏｒｙｆｕｎｃｔｉｏｎｄｉｓｔｕｒｂｅｄｂｙｏｒｇａｎｏｐｈｏｓｐｈａｔｅｐｏｉ ｓｏｎｉｎｇ[2 ,3] .Ｐｒｅｖｉｏｕｓｓｔｕｄｉｅｓｓｕｇｇｅｓｔｅｄｔｈａｔｂｅｎａ…     

Release of the antioxidants ascorbate and urate from a nitrergically-innervated smooth muscle

1. The main object of the present study was to determine whether ascorbate, an antioxidant which has been shown to protect nitric oxide (NO) from attack by scavenger molecules, might be released from nitrergically-innervated smooth muscle; ascorbate release from the rat anococcygeus was measured by use of h.p.l.c. with electrochemical detection.
2. Incubation of rat anococcygeus muscles in normal physiological salt solution (PSS; 30 min) resulted in release of ascorbate into the bathing medium (7.7±0.9 nmol g⁻¹ tissue). This release was increased by 96% when muscles were incubated in high K⁺ (70 mM) PSS. The resting release of ascorbate was unaffected by tetrodotoxin (TTX; 1 μM), ω-conotoxin GVIA (10 nM) or omission of calcium ions from the PSS (with addition of 0.2 mM EGTA), but all three procedures attenuated the increased release observed under depolarizing conditions. Resting release of ascorbate was unaffected by glutamate (100 μM), aspartate (100 μM), γ-aminobutyric acid (100 μM) or carbachol (50 μM).
3. A second h.p.l.c. peak, which always preceded the ascorbate peak, was identified as urate. Urate release from the anococcygeus, following 30 min incubation in normal PSS, was 64.6±12.7 nmol g⁻¹ tissue but, unlike ascorbate, urate release was unchanged in high K⁺ PSS. In functional experiments, urate (100–400 μM) partially protected NO (15 μM)-induced relaxations of the rat anococcygeus from inhibition by 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy-PTIO; 50 μM), but not from inhibition by hydroquinone or duroquinone (both 100 μM).
4. Muscles chemically sympathectomized with 6-hydroxydopamine (6-OHDA, 500 μM; 2 h) still exhibited release of ascorbate (2.5±0.4 nmol g⁻¹ tissue) and urate (22.2±2.9 nmol g⁻¹ tissue); in both cases the release was similar to that observed in time-matched control tissues not exposed to 6-OHDA. High K⁺ PSS produced a TTX-sensitive increase in release of ascorbate, but not urate, from 6-OHDA-treated muscles.
5. The results demonstrate that significant amounts of ascorbate and urate are released from the rat anococcygeus muscle. Ascorbate, but not urate, release appears to be enhanced by activation of nerves which are resistant to 6-OHDA pretreatment. Since both antioxidants can protect NO from attack by scavenger molecules, their release in nitrergically-innervated tissues may be important for the provision of the correct redox environment to allow NO to fulfill its proposed neurotransmitter role.

     

河豚毒素与局麻药联合应用对家兔齿髓刺激所致疼痛的对抗作用

河豚毒素(tetrodotoxin，TTX)是一种毒性极高的非蛋白神经毒素。具有很强的局麻作用。其效力比目前常用局麻药强万倍以上。持续时间长。将TTX与常用局麻药联合应用于齿髓镇痛。国内外文献尚未报道。我们设想将极微量TTX与常用局麻药利多卡因、丁卡因联合给药，通过齿髓刺激试验，测定其局部镇痛作用，观察是否具有协同或增强局麻效果，以探讨TTX作为协同局麻药应用于临床的可能。