Time-dependent effects of platelet-rich plasma on the memory and hippocampal synaptic plasticity impairment in vascular dementia induced by chronic cerebral hypoperfusion

The present study aimed to investigate the effects of early and late administration of platelet-rich plasma (PRP) on learning-memory and hippocampal synaptic plasticity impairment in rat model of vascular dementia. Sprague-Dawley rats (6-7 weeks) were randomly divided into control, sham, 2VO + V (bilateral carotid vessel occlusion + vehicle), 2VO + E-PRP (early after 2VO), and 2VO + L-PRP (late after 2VO) groups. The injection of PRP started immediately or on the day 20 after 2VO in 2VO + E-PRP and 2VO + L-PRP, respectively, and continued until 28th day (two-time a week). The passive avoidance and Morris water maze tests were used for evaluation of fear and spatial memory formation. The in-vivo long-term potentiation (LTP) was evaluated by field-potential recording, paired-pulse ratio (PPR) and input-output (I/O) curve which were monitored as indexes for evaluation of short-term plasticity (STP) and basal-synaptic transmission (BST), respectively. The 2VO decreased PPR at inter-stimuli interval (ISI) 10 ms and BST, but injection of PRP in both treated groups rescued the PPR and BST depression. In addition, the induction of LTP, fear and spatial memory performance decreased in the 2VO + V group. However, early treatment, but not late, recovered LTP and memory. The PPR and BST improved with early and late treatment; therefore, the number and time of injection seem to be not important for recovery of BST. However, we found that LTP and memory loss rescued only with early administration. Hence, timely injection, before development of the disease, or number of injections could be critical.