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Alpha-mangostin, a component of Garcinia mangostana Linn, is a xanthone derivative shown to have antioxidant and anticarcinogen properties. In this study, we first report the antimetastatic effect of alpha-mangostin in the human prostate carcinoma cell line PC-3. The results show that alpha-mangostin exhibited an inhibitory effect on the abilities of adhesion, migration, and invasion by cell-matrix adhesion assay, wound healing assay, and Boyden chamber assay. In the cancer cell metastasis process, matrix degrading proteinases are required. Results from zymography showed that alpha-mangostin treatment could decrease the expressions of matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9), and urokinase-plasminogen activator (u-PA) in a concentration-dependent manner. Moreover, alpha-mangostin also exerted an inhibitory effect on phosphorylation of c-Jun N-terminal kinase 1 and 2 (JNK1/2) and inhibition of activation of nuclear factor kappa B (NF-kappaB), c-Fos, and c-Jun. Furthermore, the treatment of inhibitors specific for JNK (SP600125) to PC-3 cells could result in a reduced expression of MMP-2, MMP-9, and u-PA. These results demonstrated that alpha-mangostin could mediate PC-3 cells metastasis by reduction of MMP-2, MMP-9, and u-PA expression through the suppression of the JNK1/2 signaling pathway and inhibition of NF-kappaB and AP-1 binding activity. These findings proved that alpha-mangostin might be offered further application as an antimetastatic agent.

Stimulation of the prefrontal cortex (PFC) has been shown to have an excitatory influence on dopamine (DA) neurons. We report here that, under nonstimulated conditions, the activity of DA neurons in the ventral tegmental area (VTA) also covaries, on a subsecond timescale, with the activity of PFC cells. Thus, in 67% of VTA DA neurons recorded in chloral hydrate-anesthetized rats, the firing of the cell displayed a slow oscillation (SO) that was highly coherent with the activity of PFC neurons. The SO was suppressed by transections immediately caudal to the PFC or by intra-PFC infusion of tetrodotoxin, suggesting that it depends on inputs derived from the PFC. Unexpectedly, the SO in most VTA DA neurons was reversed in phase relative to PFC cell activity, suggesting that at least part of PFC information is transferred to DA neurons indirectly through inhibitory relay neurons. These results, together with those reported previously, suggest that the PFC can act through multiple pathways to exert both excitatory and inhibitory influences on DA neurons. The observed functional coupling between DA and PFC neurons further suggests that these pathways not only allow a bidirectional control of DA neurons by the PFC, but also enable action potential-dependent DA release to be coordinated, on a subsecond timescale, with glutamate release from PFC terminals. Further understanding of this coordinated activity may provide important new insights into brain functions and disorders thought to involve both VTA DA and PFC neurons.

Aim: To investigate the effect of l-stepholidine (SPD) on the frequency of spontaneous excitatory postsynaptic currents (sEPSC) in the pyramidal cells between layers V and VI in the prelimbic cortex (PL)., Methods: A whole-cell patch clamp in rat brain slices was used., Results: SPD significantly increased the frequency of sEPSC in a concentration-dependent manner. A selective D1 dopamine receptor antagonist SCH23390 blocked SPD-mediated effects, whereas the D1 agonist SKF38393, but not the D2/3 antagonist sulpiride, mimicked SPD-mediated increase in the frequency of sEPSC. Moreover, both protein kinase A (PKA) inhibitor N-(2- [p-bromocinnamylamino]-ethyl)-5-isoquinolinesulfonamide hydrochloride and protein kinase C (PKC) inhibitor chelerythrine attenuated the effect of SPD on sEPSC., Conclusion: SPD elicits its effect on the frequency of sEPSC on the PL pyramidal cells via presynaptic D1 receptors, and is dependent on PKA and PKC signaling pathways.