Lobeline production by hairy root culture of Lobelia inflata L.

Hairy roots were obtained following inoculation of the stems of Lobelia inflata L. with Agrobacterium rhizogenes strain ATCC 15834. These hairy roots contained agropine and mannopine. In addition, lobeline was detected by HPLC and confirmed by mass spectrometry. Various media were tested for the growth of hairy roots as well as for the content of lobeline in hairy roots. The growth rate of hairy roots cultured in Nitsch and Nitsch's medium was approximately one third of those cultured in other media. The lobeline content of hairy roots (18–54 g/g dry weight) cultured in these media was the same order of magnitude compared with that of roots of L. inflata (24 g/g dry weight) cultivated in pots. The hairy roots cultured in Nitsch and Nitsch's medium were morphologically different from those cultured in other media.Abbreviations MS medium Murashige and Skoog's medium - 1/2 MS medium one-half strength of the standard Murashige and Skoog's medium - B5 medium Gamborg's B5 medium - NN medium Nitsch and Nitsch's medium - FW fresh weight - DW dry weight     

Effects of VMAT2 inhibitors lobeline and GZ‐793A on methamphetamine‐induced changes in dopamine release,metabolism and synthesis in vivo

Vesicular monoamine transporter‐2 (VMAT2) inhibitors reduce methamphetamine (METH) reward in rats. The current study determined the effects of VMAT2 inhibitors lobeline (LOB; 1 or 3 mg/kg) and N‐(1,2R‐dihydroxylpropyl)‐2,6‐cis‐di(4‐methoxyphenethyl)piperidine hydrochloride (GZ‐793A; 15 or 30 mg/kg) on METH‐induced (0.5 mg/kg, SC) changes in extracellular dopamine (DA) and its metabolite dihydroxyphenylacetic acid (DOPAC) in the reward‐relevant nucleus accumbens (NAc) shell using in vivo microdialysis. The effect of GZ‐793A (15 mg/kg) on DA synthesis in tissue also was investigated in NAc, striatum, medial prefrontal cortex and orbitofrontal cortex. In NAc shell, METH produced a time‐dependent increase in extracellular DA and decrease in DOPAC. Neither LOB nor GZ‐793A alone altered extracellular DA; however, both drugs increased extracellular DOPAC. In combination with METH, LOB did not alter the effects of METH on DA; however, GZ‐793A, which has greater selectivity than LOB for inhibiting VMAT2, reduced the duration of the METH‐induced increase in extracellular DA. Both LOB and GZ‐793A enhanced the duration of the METH‐induced decrease in extracellular DOPAC. METH also increased tissue DA synthesis in NAc and striatum, whereas GZ‐793A decreased synthesis; no effect of METH or GZ‐793A on DA synthesis was found in medial prefrontal cortex or orbitofrontal cortex. These results suggest that selective inhibition of VMAT2 produces a time‐dependent decrease in DA release in NAc shell as a result of alterations in tyrosine hydroxylase activity, which may play a role in the ability of GZ‐793A to decrease METH reward.

     

Differential Effect of Nicotinic Agonists on the [3H]Norepinephrine Release from Rat Hippocampal Slices

The aim of this study was to investigate the mechanisms involved in the effect of nicotinic agonists on the [³H]norepinephrine ([³H]NE) release from rat hippocampal slices. The stimulatory effect of nicotine, cytisine, epibatidine and anatoxin-A was completely blocked by the nicotinic antagonist mecamylamine (10 M). In contrast, the effect of dimethylphenylpiperazinium (DMPP) was only partially inhibited by mecamylamine but was completely blocked by the NE uptake inhibitor desipramine (DMI, 10 M). Finally, the effect of lobeline was not affected by mecamylamine and was only partially blocked by DMI. Our data indicate that the majority of nicotinic agonists increase the release of [³H]NE exclusively via stimulation of nicotinic acetylcholine receptors (nAChRs). DMPP, in addition to the stimulation of nAChRs, also evokes a carrier-mediated release. Lobeline has no stimulatory effect on nAChRs, induces a carrier-mediated release and has a further action of unidentified mechanism. Our results suggest that special caution is required for the interpretation of data, when DMPP or lobeline are used as nicotinic agonists.     

胆碱能N_1受体激动剂洛贝林对豚鼠心室乳头肌电生理及收缩力的影响

本实验观察了在存在M受体阻断剂阿托品(2μM)的情况下,胆碱能N_1受体激动剂洛贝林(lobeline)对儿茶酚胺耗竭的豚鼠心室乳头肌电活动及收缩力的影响。洛贝林(0.5—8μM)使动作电位时程(APD)显著延长,动作电位0期最大除极速率(V_(max))和动作电位幅值(APA)下降,心肌收缩力(FC)减弱,以及收缩峰值出现时间(time-to-Peak force,TTP)提前。N_1 受体阻断剂六甲双铵(hexamethonium,10μM)使洛贝林对APD的剂量-反应曲线平行右移。这些实验结果提示:在豚鼠心室肌可能存在胆碱能N受体。