Current perspectives on the antidepressant-like effects of guanosine

Purines have a recognized importance as intercellular mes- sengers. These molecules play an important role in the de- velopment and maintenance of the central nervous system （CNS）, as well as in its response to pathological conditions. Both adenine and guanine-based purines can be released from astrocytes, where they play a relevant role as extracel- lular signaling molecules. Particularly, the nucleoside gua- nosine has been proposed as an extracellular molecule that regulates the response of CNS to damage. Following injury, this nucleoside attains high concentrations in the extracel- lular space, where it activates multiple signaling pathways.

Doubt about antidepressant-like effect

Dear Editor： Extensive studies have measured antidepressant- like effects of chemical compounds to discover new drugs for depression treatment or to clarify the mo- lecular mechanisms of depression. Most useful anti- depressants including tricyclics, selective serotonin reuptake inhibitors （SSRIs）, noradrenaline reuptake inhibitors （NRIs）, serotonin and noradrenaline re- uptake inhibitors （SNRIs）, and monoamine oxidase inhibitors （MAOIs） exert antidepressant-like effects in forced swimmin~ test （FST） in mice and rats[1].

Antidepressant Effects of Ginsenosides from Panax notoginseng

Ginsenosides Rg 1,Rb 1,R 1,Rd,and Re are major constituents of Panax notoginseng,a famous traditional Chinese medicinal herb,which has both stimulative and inhibitory effects on the central nervous system (CNS).The monoamine hypothesis proposes that depression is a result of the depletion of 5-hydroxytryptamine (5-HT),norepinephrine (NE) and dopamine (DA) in addition to the activation of monoamine oxidase in the CNS.The purpose of this study was to determine whether P.notoginseng Saponin (PNS) has an antidepressant activity.We investigated the antidepressant-like activities of Rg 1,Rb 1,R 1,Rd,and Re in mice,using two animal models of depression.In addition,we analyzed the neurochemicals by the chronic unpredictable mild stress test.Our results showed that Rb 1,Rd,and Re treatment at 10 mg kg-1 significantly reduced the duration of immobility in both the tail suspension and forced swimming tests.Rb 1,Rd,and Re increases in 5HT and NE levels at 10 mg kg-1 in both the frontal cortex and hippocampus.Dopamine levels increased in the hippocampus and the striatum.Moreover,5-hydroxyindoleacetic acid (5-HIAA) levels were found increased in the hippocampus.These findings suggest that the antidepressant effects of Rb 1,Rd,and Re may be related to the increase in 5-HT and NE in the CNS,and through the alterations in the synthesis or metabolism of dopamine.

Traditional herbal formula Sini Powder extract produces antidepressantlike effects through stress-related mechanisms in rats

Sini Powder(SP), a traditional Chinese herbal formula, has long been used to treat depression in patients, although the underlying mechanisms remain to be elucidated. In the present study, we found that rats treated with SP extract for 7 days showed a significant increase in swimming time and reduction in immobility time in forced swimming test in a dose-dependent manner, without changes in locomotion. These effects could be attributed to SP's modulation of the hypothalamus-pituitary-adrenal axis, because a single pretreatment of SP extract could rescue increased serum corticosterone and plasma adrenocorticotropin levels induced by acute elevated platform stress. A single pretreatment of SP extract could also elevate the m RNA expression of hippocampal glucocorticoid receptors. In conclusion, our results suggest that SP extract may act as an anti-stress medication to produce antidepressant-like effects.