Decline of learning and memory in senility and expression of cyclin-dependent kinase-5 in brain development of rats

Hongli LI; Zhong YANG; Yu SUN; Zegui LI; Wenqin CAI

ABSTRACT

BACKGROUND:

Cyclin-dependent kinase-5 (CDK-5) is one of the members in cyclin-dependent protein kinase family. The attention has being drawn by researchers on the relationship between the expression and distribution of CDK-5 mRNA and its protein in the brain during brain development and neural degeneration in thought-cognition.

OBJECTIVE:

To probe into the influence of CDK-5 on neurogeny and neural degeneration during cerebral development.

DESIGN:

Single factor analysis of variance.

SETTING:

Histological and Embryological Department and Neurobiological Department in Third Military Medical University of Chinese PLA.MATERIALS The experiment was performed in Histological and Embryological Department and Neurobiological Department in Third Military Medical University of Chinese PLA. Twenty-five Wistar rats of 5 phases were employed, named embryonicphase (E8-E21), neonatal phase (P0-P15),childhood (P16-2 months), grown-up phase (＞ 2 months) and senile phase (＞ 8 months), 5 rats in each group.

METHODS:

In situ hybridization histochemistry (ISH) and immunohistochemistry (IHC) staining was adopted in brain sections from embryonic phase to senile phase.MAIN OUTCOME MEASURFS Distribution and expression of positive cells of CDK-5 mRNA and protein in various brain areas.

RESULTS:

Twenty-five rats entered result analysis for all. ① The expression of CDK-5 mRNA presented in entire development from E14 to P350and was in tendency of stability after growth-up. CDK-5 mRNA localized mainly in neurons and positive regions distributed mainly in cerebral cortex, hippocampus, thalamus, hypothalamus, cerebellum and a part of nerve nuclei. ② The expression of CDK-5 was strong after birth and it was weaker in embryonic and senile rats. Positive regions concentrated mainly in peripheral ventricle, hippocampus, cerebellum and a part of nerve nuclei.The expression only presented in hippocampus and Purkinje cellular layer of cerebellum in senile rats.

CONCLUSION:

CDK-5 in brain runs through entire phases of neural development, it expresses more significantly in neonatal phase and childhood and declines after growth-up, especially in senile phase. The declined expression of CDK-5 in hippocampus of senile rats is closely associated with decline of learning and memory in senility probably.