Nowadays the pathogenesis of early-onset depression is still uncertain. Only SSRIs are currently approved for clinical use as antidepressants in children and adolescents, indicating that 5-HT is the most important neurotransmitter involved in the dis-ease. Current studies with regard to central 5-HTergic system in early-onset depression mainly focus on 5-HT synthesis deficien-cy, 5-HT transportation dysregulation, as well as the earlier mat-uration of 5-HT system than norepinephrine system. 5-HT precur-sor tryptophan malabsorption and dysregulation of 5-HT synthesis can contribute to 5-HT deficiency. Moreover, the 5-HTTLPR low-expressing genotypes may increase the risk of early-onset de-pression. It is necessary to make preclinical and clinical studies more widely and deeply about the effect of central 5-HTergic sys-tem in early-onset depression in future.

Objective To observe the effects of kidney-tonifying therapy on spatial learning, memory abilities and ultrastructure of hippocampal dentate gyrus ( DG ) cells of kidney deficiency rats induced by sexual intemperance. Methods SD rats with low reproductive capacity were caused by continuously mating for 6 months, and then were randomly divided into 5 groups, namely model group, low- and high-dose of Liuwei Dihuang pills (LDP) groups (in the dosage of 4.8, 9.6 g·kg-1·d-1), low-and high-dose of Jingui Shenqi pills (JSP) group (in the dosage of 5.2, 10.4 g·kg-1·d-1), 8 rats in each group. Except the model group, the other groups were respectively given with the corresponding medication. SD rats aged 2 months served as the normal control group. After treatment for 30 continuous days, the learning and memory abilities of rats were examined by Morris Water Maze. The cell ultra structure of hippocampal dentate gyrus was observed by transmission electron microscopy. Results The results of the place navigation test of Morris water maze showed that the escape latency of rats was prolonged obviously in the model group compared with that of the normal control group (P<0.01), and the escape latency of rats in the medication groups was shorter than the kidney deficiency model group (P<0.05 or P<0.01). The results of spatial probe test showed that the residence time in the former hidden platform quadrant and its surrounding area was significantly shortened in the model group compared with that of the normal control group ( P<0.01) , but was prolonged after medication of high-dose JSP ( P<0.05 or P<0.01 compared with that of the model group). Under the electron microscope, the cell ultra structure lesions of hippocampal dentate gyrus were much relieved in the high-dose LDP group, and high-dose JSP group as compared with those of the model group. Conclusion ( 1) Long-term sexual intemperance can impair spatial learning and memory abilities and causes the cell ultra structure lesions of hippocampal dentate gyrus of rats. (2) The kidney-tonifying therapy can significantly alleviate the spatial learning and memory disturbance and the cell ultra structure lesions of hippocampal dentate gyrus induced by sexual intemperance. ( 3) There are not significant differences between the two kidney-tonifying therapies in improving spatial learning and relieving cell ultra structure lesions. The effect of JSP on improving spatial memory abilities is better than that of LDP.