In vitro accumulation of tetrodotoxin in pufferfish liver tissue slices.

The liver tissue slices of pufferfish accumulate in vitro tetrodotoxin (TTX), when incubated with minimum essential medium containing TTX. In the case of Takifugu rubripes liver slices incubated at a concentration of 25 microg TTT/ml, TTX of 3.9 microg/g was first detected at 2h and increased to 15 microg/g at 48h. The TTX content accumulated was not decreased, even when the slices were further incubated without TTX for additional 48h. Another species of pufferfish T. paradalis also showed similar trend in TTX accumulation, except they accumulated higher concentration of TTX (36.4 microg/g at 48h) than T. rubripes. On the contrary, in the cases of the liver slices from parrot-bass Oplegnathus fasciatus, green ling Hexagrammos otakii and filefish Thamnaconus modestus incubated at a concentration of 25 microgTTX/ml, TTX of 3-4 microg/g was detected even at 0.5h. However, no significant change in TTX contents was recognized during the incubation for 48h. Further incubation of the filefish liver slices without TTX for additional 48h did not decrease the TTX content. It is unlikely that the liver slices of filefish as well as pufferfish rapidly excrete TTX. These results suggest that the difference in the accumulation of TTX between pufferfish and filefish livers is ascribable to the difference not in the TTX excreting ability but in the ability to take up TTX.     

Single-channel analysis of tetrodotoxin-sensitive and tetrodotoxin-resistant sodium channels in rat dorsal root ganglion neurons

Tetrodotoxin-sensitive and tetrodotoxin-resistant single sodium channel currents were recorded from rat dorsal root ganglion neurons. The two types of sodium channel currents could be distinguished by the effects of predepolarization, 10 nM tetrodotoxin, and the inactivation during depolarization. Single-channel conductances were calculated to be 6.3 and 3.4 pS in the tetrodotoxin-sensitive and tetrodotoxin-resistant channels, respectively.     

Effects of Continuous Sciatic Nerve Block by Tetrodotoxin on Growth Associated Protein-43 Expression in Dorsal Root Ganglions of Normal and Sciatic Nerve Injury Rats

Growth associated protein-43(GAP-43) is considered to be one of the most useful molecular markers for the neural development,nerve regeneration,and neuroplasticity     

Influence of tetrodotoxin and calcium on changes in extracellular dopamine levels evoked by systemic nicotine

The influence of tetrodotoxin (TTX) and calcium on the increase of extracellular dopamine (DA) levels in the nucleus accumbens (NAcc), evoked by the systemic administration of nicotine, cocaine andd-amphetamine, have been studied in conscious, freely moving rats using in vivo microdialysis. TTX (10^–6 M), administered via the dialysis probe, completely abolished (P<0.01) the elevations in extracellular DA, DOPAC and HVA seen following nicotine (0.4 mg/kg SC). The removal of calcium with the inclusion of diaminoethanete-traacetic acid (EDTA 10^–4 M) in the Ringer solution was also associated with inhibition (P<0.01) of the nicotine-induced changes in these parameters. The systemic administration of cocaine (15 mg/kg IP) andd-amphetamine (0.5 mg/kg SC) caused elevations in extracellular DA (P<0.01) accompanied by significant decreases (P<0.01) in HVA levels. DOPAC levels were also significantly (P<0.01) lowered byd-amphetamine treatment. The presence of TTX and removal of calcium with addition of EDTA completely abolished the changes in NAcc DA and HVA induced by cocaine. TTX had no influence on thed-amphetamine evoked responses in NAcc DA. However, the metabolites, which were markedly reduced by the TTX, were not further decreased by the systemic administration ofd-amphetamine. NAcc DA was significantly (P<0.01) raised followingd-amphetamine in the absence of calcium and presence of EDTA. However, this was significantly (P<0.01) attenuated in comparison to that seen in the presence of calcium. The results support the conclusion that, at the dose tested, nicotine evokes increases in extracellular NAcc DA levels by calcium and impulse-dependent mechanisms. Moreover, the data are also consistent with a partial calcium-dependent component ind-amphetamine-induced stimulation of this system in vivo.     

Effects of electrical stimulation and tetrodotoxin paralysis on antigenic properties of acetylcholine receptors in rat skeletal muscle

To examine the role of muscle activity in the expression of fetal- and adult-type acetylcholine receptors (AChRs), we studied the effects of muscle stimulation in cell culture and of tetrodotoxin (TTX)-induced paralysis and denervation in adult rat muscles. The AChR content of these muscles was determined using [¹²⁵I]-bungarotoxin and the proportion of fetal-type receptors was estimated using a radioimmunoprecipitation assay with a myasthenic serum that was highly specific for fetal-type receptors. We found that both stimulated, aneural muscle cells in vitro and inactive muscles in vivo produced predominantly fetal-type AChRs. However the TTX-paralysed muscles had a lower proportion of fetal-type receptors than the denervated muscles. We conclude that neither muscle activity nor innervation alone, but a combination of both, is required for full regulation of AChR antigenicity.     

Distribution of tetrodotoxin in the body of the blue-ringed octopus (Hapalochlaena maculosa).

Tetrodotoxin (TTX) was quantitatively assayed in six specimens of semi-adult blue-ringed octopus, Hapalochlaena maculosa, by a post-column fluorescent-HPLC system. TTX was found to be present in all body parts, e.g. in high concentrations in the arms followed by the abdomen and cephalothorax. The toxin is not associated exclusively with the posterior salivary gland.     

急性河豚中毒患者脑氧供需平衡变化的临床研究

目的　探讨急性河豚毒素 (TTX)中毒患者颈静脉血氧饱和度 (SjO2 )、动脉 颈内静脉血氧含量差 (AVDO2 )、脑氧摄取 (CEO2 )变化与预后的关系。方法　观察 34例TTX中毒患者 6～ 12h、 2 4h、 4 8h、 72h、 7d各时间点SjO2 、AVDO2 、CEO2 的变化。结果　TTX中毒患者入院 6～ 12h时SjO2 、AVDO2 、CEO2 明显高于对照组 (P <0 0 5 ) ,入院 2 4h后TTX中毒患者SjO2 逐渐恢复正常 ,但重度组AVDO2 、CEO2 明显低于对照组 (P <0 0 1) ,当CEO2 低于 2 5 %时 ,患者预后差。结论　脑氧供需平衡变化反映了TTX中毒患者大脑神经细胞的机能和利用氧的能力 ,因此可将脑氧供需平衡变化作为判断TTX中毒预后的重要指标     

Isolation and characterization of bacteria from the copepod Pseudocaligus fugu ectoparasitic on the panther puffer Takifugu pardalis with the emphasis on TTX.

A total of 50 bacterial isolates was obtained from the copepod Pseudocaligus fugu, which is a common parasite, collected from the body surface of the panther puffer Takifugu pardalis. On the basis of colony characteristics, these bacterial isolates were grouped into six types, of which only two (Types-I and -II) showed a high affinity for adhesion to the carapace of the banana shrimp Penaeus merguiensis. These two types of adhesive bacteria were identified through 16S rRNA sequence analysis as Shewanella woodyi (Type-I) and Roseobacter sp. (Type-II). Representative isolates of these two adhesive bacteria were examined for tetrodotoxin (TTX) production by high-performance liquid chromatography (HPLC)-fluorometric system, gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS). It was rather unexpectedly revealed that TTX and anhydroTTX were present in the supernatant of culture of the Type-II isolate Roseobacter sp.