Piracetam improves cognitive deficits caused by chronic cerebral hypoperfusion in rats

Abstract

Piracetam is the derivate of gamma-aminobutyric acid, which improves the cognition,memory,consciousness, and is widely applied in the clinical treatment of brain dysfunction. In the present experiments, we study the effects of piracetam on chronic cerebral hypoperfused rats and observe its influence on amino acids, synaptic plasticity in the Perforant path-CA3 pathway and apoptosis in vivo. Cerebral hypoperfusion for 30 days by occlusion of bilateral common carotid arteries induced marked amnesic effects along with neuron damage, including: (1) spatial learning and memory deficits shown by longer escape latency and shorter time spent in the target quadrant; (2) significant neuronal loss and nuclei condensation in the cortex and hippocampus especially in CA1 region; (3) lower induction rate of long term potentiation, overexpression of BAX and P53 protein, and lower content of excitatory and inhibitory amino acids in hippocampus. Oral administration of piracetam (600 mg/kg, once per day for 30 days) markedly improved the memory impairment, increased the amino acid content in hippocampus, and attenuated neuronal damage. The ability of piracetam to attenuate memory deficits and neuronal damage after hypoperfusion may be beneficial in cerebrovascular type dementia.

Fig. 1

A typical evoked potential recorded in hippocampus CA3 region, population spike was defined as the amplitudes from the first positive peak (a) to negative peak (b)

Fig. 2

Effect of piracetam on cerebral hypoperfusion-induced deficits in learning and memory in rats performing the Morris water maze. The task was performed with four trials per day during 5 days for the acquisition test (A), and performed with four trials on day 6 without the platform for retention test (B). (C) shows the typical swim-tracking path in probe trial on the sixth training day (no platform). Rats were administrated piracetam (oral administration of piracetam 600 mg/kg, once per day for 30 days, Piracetam-treated, n = 10) after surgery, pretreated with saline (1 ml/kg, HP, n = 10). The sham-operated group (Sham-operated, n = 10) was treated with only saline without induction of hypoperfusion. Significance with Tukey’s test following a repeated ANOVA is indicated as ^* P < 0.01 versus Sham-operated and ^# P < 0.05 versus HP. Vertical lines indicate SEM (N = 10)

Fig. 3

Representative photographs showing the rats hippocampus and cerebral cortex. Sections from three rats in each group were examined. A and D: Sham-operated group; B and E: HP group; C and F: Piracetam-treated group. Scale bars represent 50 μm

Fig. 4

Effects of piracetam on morphologic changes in rats hippocampus and cerebral cortex induced by chronic hypoperfusion. Sections from three rats in each group were examined. Rats were administrated piracetam (oral administration of piracetam 600 mg/kg, once per day for 30 days, Piracetam-treated, n = 3) after surgery, pretreated with saline (1 ml/kg, HP, n = 3). The sham-operated group (Sham-operated, n = 3) was treated with only saline without induction of hypoperfusion. Significance with Tukey’s test following a repeated ANOVA is indicated as ^* P < 0.01 versus Sham-operated and ^# P < 0.05 versus HP. Vertical lines indicate SEM (N = 3)

Fig. 5

Representative photographs show effects of piracetam on apoptotic related protein expression in cortical region of rats chronically hypoperfused after ligation of the bilateral carotid arteries. A and D: Sham-operated; B and E: Ischemia group; C and F: piracetam 600 mg/kg. Scale bars represent 50 μm. Arrows indicate positive immunoreactivity cells

Fig. 6

Effects of piracetam on apoptotic related protein expression in cortical region of rats chronically hypoperfused after ligation of the bilateral carotid arteries. The relative optical density as % values of immunoreactivity is also represented. Rats were administrated piracetam (oral administration of piracetam 600 mg/kg, once per day for 30 days, Piracetam-treated, n = 3) after surgery, pretreated with saline (1 ml/kg, HP, n = 3).The sham-operated group (Sham-operated, n = 3) was treated with only saline without induction of hypoperfusion. Significance with one-way analysis of variance followed by the Duncan’s new multiple range method or Newman–Keuls test is indicated as ^* P < 0.01 versus Sham-operated and ^# P < 0.05 versus HP. Vertical lines indicate SEM (N = 3)

Fig. 7

(A) Changes in LTP after cerebral hypoperfusion in the perforant path-CA3 synapses. LTP was blocked in the HP group. Piracetam ameliorated the inhibition. (B) Changes of the amplitude of the population spike pre-tetanus and post-tetanus (HFS). I and IV: Sham-operated group (treated with only saline, Sham-operated, n = 7); II and V: HP group (pretreated with saline 1ml/kg, HP, n = 7); III and VI: Piracetam-treated group (oral administration of piracetam 600 mg/kg, once per day for 30 days, Piracetam-treated, n = 8); I, II ,III before HFS; IV, V ,VI after HFS. Significant differences of post-hoc analysis are indicated as ^* P < 0.01 versus sham-operated and ^# P < 0.05 versus HP. Vertical lines indicates SEM (N = 7–8)

Fig. 8

Effects of piracetam on the content of amino acids. Rats were administrated piracetam (oral administration of piracetam 600 mg/kg, once per day for 30 days, Piracetam-treated, n = 8) after surgery, pretreated with saline (1 ml/kg, HP, n = 7). The sham-operated group (Sham-operated, n = 7) was treated with only saline. Significance with one-way analysis of variance (ANOVA) followed by the Fisher LSD test is indicated as ^& P < 0.05 versus Normal group, ^* P < 0.05 versus Sham-operated group and ^# P < 0.05 versus HP group. Vertical lines indicates SEM (N = 7–8)