The 2-oxopyrrolidinacetamide piracetam reduces infarct brain volume induced by permanent middle cerebral artery occlusion in male rats
Introduction
Piracetam (2-oxopyrrolidinacetamide), a low-molecular-weight derivative of γ-aminobutyric acid, is widely used in clinical practice as a nootropic agent. In fact, it has been reported that piracetam is able to improve higher cerebral integrative functions including those involved in cognitive processes such as learning and memory (Giurgea, 1976).
In addition to its nootropic properties, piracetam has been also shown to exert a protective effect on brain function against hypoxic insults both in experimental animals and humans. In fact, it has been reported that this agent is able to reduce the amnesic effect of hypoxia in rats (Sara and Lefevre, 1972) and the brain recovery time after readmission of air to hypoxic rabbits (Giurgea et al., 1970). Furthermore, more recently it has been shown that piracetam restores dopamine release impaired by hypoxia (Wustmann et al., 1982) and improves cortical neuronal responsiveness to cutaneous stimulation after focal brain injury (Coq and Xerry, 1999).
In regard to studies performed in humans, it has been reported that piracetam increases compromised regional cerebral blood flow (Platt et al., 1992) and exerts a beneficial effect on neuronal metabolism, increasing the impaired glucose and oxygen cerebral metabolic rate when studied by positron emission tomography scan in the infarcted and adjacent brain tissue in acute stroke patients (Heiss et al., 1983, Depresseux et al., 1986). Furthermore, a neuroprotective effect of piracetam in the early therapy of acute hemispheric stroke has been reported (De Deyn et al., 1997. Finally, it has been demonstrated that piracetam can also improve neurologic functions impaired by stroke such as aphasia (Enderby et al., 1994, Huber, 1999) and palatal myoclonus (Karacostas et al., 1999).
In the present study, the possibility that piracetam could directly influence the extent of the infarcted brain region following acute stroke was investigated. For this purpose, the permanent middle cerebral artery occlusion (pMCAO) model was used in male rats. Brain infarct area was evaluated by 2,3,5-triphenyl tetrazolium chloride (TTC) method staining (Bederson et al., 1986). Piracetam (125, 250, and 500 mg/kg) was administered intraperitoneally three times at 6, 9, and 22 h after pMCAO. This time schedule was chosen on the basis of the results showing that the infarct size, detected 24 h after pMCAO, was significantly larger than that measured after 6 and 9 h respectively. This means that at these times ischemic damage is not yet complete and therefore a possible protective agent administered 6 and 9 h after pMCAO still has the possibility to induce a reduction of brain infarct. In addition, to ensure that piracetam treatment really prevented and not simply delayed neuronal damage after pMCAO, the drug effect on the extent of brain infarct volume was evaluated also 48 h and 7 days after the ischemic insult.
Section snippets
Experimental groups
Sprague–Dawley male rats (Charles River, Italy) weighing 250–270 g were housed under diurnal lighting conditions (12 h darkness and 12 h light) and fasted overnight but allowed free access to water before the experiment. Each experimental group consisted of 5–8 animals. Experiments were performed according to international guidelines for animal research and the experimental protocol was approved by Animal Care Committee of the University of Naples.
Permanent middle cerebral artery occlusion
Animals were anesthetized intraperitoneally
Time course of the development of brain infarct after pMCAO in Sprague–Dawley male rats
Infarct area enlarged progressively and in a time-dependent way after 3, 6, 9, and 24 h of ischemia. In particular, infarct size was small 3 h after pMCAO and significantly increased after 6 h. At the 9th hour the size was not significantly different from that detected at 6 h, whereas at the 24th hour it doubled the value detected at 9 h (Fig. 1).
Effects of increasing doses of piracetam on infarct area size resulting from pMCAO
In rats receiving vehicle, at the 24th h, pMCAO caused large brain infarcts involving predominantly striatum and fronto-temporoparietal cortex. The
Discussion
The results of the present study showed that piracetam produced a marked reduction of brain infarct volume induced by pMCAO in male rats. Piracetam was administered 6, 9, and 22 h after pMCAO since the study of the time course of the development of cerebral infarct after pMCAO showed that the infarct size obtained 24 h after pMCAO was significantly larger than that evaluated 6 and 9 h after pMCAO. The rationale for administering piracetam 6 h after pMCAO and for continuing its administration 22
Acknowledgements
This work was supported by the following grants: CNR 99.02371 CT04; MURST COFIN 1999 and 2000 to LA; Ministero della Sanità “Programma per la ricerca finalizzata 1998” to SA. In addition this work was partially supported by UCB-Pharma Italia and Belgique.
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