Preproapamin genes were amplified by RT-PCR from total RNA from the venom glands of 2 honeybee species, Apis mellifera, A. cerana cerana, and 4 wasp species, Vespa magnifica, V. velutina nigrothorax and Polistes hebra...Preproapamin genes were amplified by RT-PCR from total RNA from the venom glands of 2 honeybee species, Apis mellifera, A. cerana cerana, and 4 wasp species, Vespa magnifica, V. velutina nigrothorax and Polistes hebraeus, respectively. Their PCR products were ligated into pGEM -T easy vector and the nucleotide sequences analyzed. The six fragments were all 141?bp in length and contained a n ORF coding the precursor of apamin. The apamin precursors of V. magnifica, V. velutina nigrothorax and P. hebraeus had 95% and 93% similarity with that of A. melliera in nucleotide and amino acid sequences, respectively. That of Vespu la maculifrons was identical to that of A. mellifera in nucleotide and amino acid sequences. Apamin precursors of V. magnifica, P. hebraeus and V. velutina nigrothorax also had the same nucleotide sequences. The nucleotide sequences o f preproapamin genes from the Chinese honeybee, A. cerana cerana and 4 wasp sp ecies are described for the first time. A notable discovery was that the wasps species had exactly same apamins as the honeybees despite the fact they belong to different insect families.展开更多
The ventral tegmental area dopamine (DA VTA) neurons have the spontaneous tonic activity and an alteration of firing pattern from tonic to burst accelerates dopamine transmission more effectively in the mesoaccumbal d...The ventral tegmental area dopamine (DA VTA) neurons have the spontaneous tonic activity and an alteration of firing pattern from tonic to burst accelerates dopamine transmission more effectively in the mesoaccumbal dopaminergic system, leading to the reinforcing process of drugs of abuse such as alcohol and nicotine. In the present study, we examined whether a persistent Na+ current would contribute to burst firing in DA VTA neuronsusing nystatin-perforated recording. Tetrodotoxin (TTX) (1 μM) or riluzole (10 μM) hyperpolarized the membrane potential and stopped spontaneous firing of DA VTA neurons. In voltage-clamp analysis, a TTX and riluzole-sensitive and persistent Na+ current was activated at ?60 mV and reached maximal amplitude at ?40 mV. This persistent Na+ current was potentiated by a negative shift of the voltage of activation by eliminating Ca2+ from the extracellular solution. The Ca2+-free extracellular solution depolarized the membrane potential and increased the firing frequency of DA VTA neurons. When a continuous hyperpolarizing current was injected, the firing pattern of the DA VTA neurons transformed into burst-like firing;with average spike number of 4.9, average inter-spike interval of 221 ms, and an average plateau potential, on which the train of spikes generated, was 11 mV. The burst-like firing of DA VTA neurons was abolished by 10 μM riluzole. The concurrent blockade of both T-type Ca2+ current and small conductance Ca2+-activated K+(SK) currents by 100 μM nickel did not induce burst-like firing with or without continuous hyperpolarizing current injection in DA VTA neurons. In conclusion, increases in a persistent Na+ current that mediates a depolarizing driving force by removing extracellular Ca2+ contributes to burst-like firing in DA VTA neurons.展开更多
文摘Preproapamin genes were amplified by RT-PCR from total RNA from the venom glands of 2 honeybee species, Apis mellifera, A. cerana cerana, and 4 wasp species, Vespa magnifica, V. velutina nigrothorax and Polistes hebraeus, respectively. Their PCR products were ligated into pGEM -T easy vector and the nucleotide sequences analyzed. The six fragments were all 141?bp in length and contained a n ORF coding the precursor of apamin. The apamin precursors of V. magnifica, V. velutina nigrothorax and P. hebraeus had 95% and 93% similarity with that of A. melliera in nucleotide and amino acid sequences, respectively. That of Vespu la maculifrons was identical to that of A. mellifera in nucleotide and amino acid sequences. Apamin precursors of V. magnifica, P. hebraeus and V. velutina nigrothorax also had the same nucleotide sequences. The nucleotide sequences o f preproapamin genes from the Chinese honeybee, A. cerana cerana and 4 wasp sp ecies are described for the first time. A notable discovery was that the wasps species had exactly same apamins as the honeybees despite the fact they belong to different insect families.
文摘The ventral tegmental area dopamine (DA VTA) neurons have the spontaneous tonic activity and an alteration of firing pattern from tonic to burst accelerates dopamine transmission more effectively in the mesoaccumbal dopaminergic system, leading to the reinforcing process of drugs of abuse such as alcohol and nicotine. In the present study, we examined whether a persistent Na+ current would contribute to burst firing in DA VTA neuronsusing nystatin-perforated recording. Tetrodotoxin (TTX) (1 μM) or riluzole (10 μM) hyperpolarized the membrane potential and stopped spontaneous firing of DA VTA neurons. In voltage-clamp analysis, a TTX and riluzole-sensitive and persistent Na+ current was activated at ?60 mV and reached maximal amplitude at ?40 mV. This persistent Na+ current was potentiated by a negative shift of the voltage of activation by eliminating Ca2+ from the extracellular solution. The Ca2+-free extracellular solution depolarized the membrane potential and increased the firing frequency of DA VTA neurons. When a continuous hyperpolarizing current was injected, the firing pattern of the DA VTA neurons transformed into burst-like firing;with average spike number of 4.9, average inter-spike interval of 221 ms, and an average plateau potential, on which the train of spikes generated, was 11 mV. The burst-like firing of DA VTA neurons was abolished by 10 μM riluzole. The concurrent blockade of both T-type Ca2+ current and small conductance Ca2+-activated K+(SK) currents by 100 μM nickel did not induce burst-like firing with or without continuous hyperpolarizing current injection in DA VTA neurons. In conclusion, increases in a persistent Na+ current that mediates a depolarizing driving force by removing extracellular Ca2+ contributes to burst-like firing in DA VTA neurons.
