Inhibition of NGF-induced neurite outgrowth of rat pheochromocytoma cells (PC12) following administration of dioxyamphetamine

The role of neurotrophic factors in manic-, anxious- and depressive-like behaviors induced by amphetamine sensitization: Implications to the animal model of bipolar disorder

BACKGROUND

Bipolar disorder (BD) and substance use disorders share common symptoms, such as behavioral sensitization. Amphetamine-induced behavioral sensitization can serve as an animal model of BD. Neurotrophic factors have an important role in BD pathophysiology. This study evaluated the effects of amphetamine sensitization on behavior and neurotrophic factor levels in the brains of rats.

METHODS

Wistar rats received daily intraperitoneal (i.p) injections of dextroamphetamine (d-AMPH) 2 mg/kg or saline for 14 days. After seven days of withdrawal, the animals were challenged with d-AMPH (0.5 mg/kg, i.p) and locomotor behavior was assessed. In a second protocol, rats were similarly treated with d-AMPH (2 mg/kg, i.p) for 14 days. After withdrawal, without d-AMPH challenge, depressive- and anxiety-like behaviors were evaluated through forced swimming test and elevated plus maze. Levels of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), neurotrophin 3 (NT-3), neurotrophin 4/5 (NT-4/5) and glial-derived neurotrophic factor (GDNF) were evaluated in the frontal cortex, hippocampus, and striatum.

RESULTS

D-AMPH for 14 days augmented locomotor sensitization to a lower dose of d-AMPH (0.5 mg/kg) after the withdrawal. d-AMPH withdrawal induced depressive- and anxious-like behaviors. BDNF, NGF, and GDNF levels were decreased, while NT-3 and NT-4 levels were increased in brains after d-AMPH sensitization.

LIMITATIONS

Although d-AMPH induces manic-like behavior, the mechanisms underlying these effects can also be related to phenotypes of drug abuse.

CONCLUSIONS

Together, vulnerability to mania-like behavior following d-AMPH challenge and extensive neurotrophic alterations, suggest amphetamine-induced behavioral sensitization is a good model of BD pathophysiology.

Claulansine F promotes neuritogenesis in PC12 cells via the ERK signaling pathway

AIM

To study the effects of Claulansine F (Clau F), a carbazole alkaloid isolated from the stem of Clausena lansium (Lour) Skeels, on neuritogenesis of PC12 cells, and to elucidate the mechanism of action.

METHODS

Neuritogenesis of PC12 cells was quantified under an inverted microscope. Expression of the neurite outgrowth marker GAP-43 was detected using immunofluorescence. GAP-43 transcription was measured using RT-PCR. Cell viability was evaluated with MTT assay. The levels of phosphor-ERK1/2, phosphor-CREB, phosphor-AKT and acetylate-p53 in the cells were examined using Western blotting analyses.

RESULTS

Clau F (10-100 μmol/L) significantly increased the percentage of PC12 cells bearing neurites. Clau F markedly increased the expression of GAP-43 in the cells. The efficiency of Clau F (10 μmol/L) in increasing neuritogenesis and GAP-43 expression was comparable to that of nerve growth factor (50 ng/mL). In addition, Clau F completely blocked the proliferation of PC12 cells within 7 d of incubation, whereas it did not cause cell death in cultured rat cortical neurons. Treatment of PC12 cells with Clau F activated both ERK and AKT signaling pathways. Co-treatment of PC12 cells with the specific ERK inhibitor PD98059, but not the specific PI3K inhibitor LY294002, blocked Clau F-induced neuritogenesis and GAP-43 upregulation.

CONCLUSION

Clau F promotes neuritogenesis in PC12 cells specifically via activation of the ERK signaling pathway.