The 2-oxopyrrolidinacetamide piracetam reduces infarct brain volume induced by permanent middle cerebral artery occlusion in male rats

Abstract

In this study, the temporal development of focal cerebral infarction induced by permanent middle cerebral artery occlusion (pMCAO) and the effects of piracetam, a derivative of γ-aminobutyric acid widely used in clinical practice as a nootropic agent, on infarct area and volume were investigated. pMCAO caused a cerebral infarct whose size progressively increased after 3, 6, 9, and 24 h. Piracetam (125 mg/kg i.p.), administered 6, 9, and 22 h after pMCAO, did not reduce pMCAO-induced brain infarct area size detected at the 24th hour. By contrast, when this agent was administered at the doses of 250 and 500 mg/kg, it caused a marked reduction of the infarct area size. This reduction was observed in almost every brain slice affected by pMCAO, although statistical differences (p <0.05) were detected in slices located at 3–5.5 mm posterior to the anterior pole in animals treated with 250 mg/kg piracetam and in slices located at 3.5–5 mm in those receiving 500 mg/kg. When the mean total volumes of brain infarct resulting from pMCAO were calculated, it was observed that in animals which had received piracetam (250 or 500 mg/kg) infarction volume was markedly (≈50%) and significantly (p <0.05) reduced in comparison with saline injected rats. Finally, piracetam (250 mg/kg administered i.p. 6, 9, and 22 h after the ischemic insult) significantly reduced brain infarct area evaluated 48 h and 7 days after pMCAO.

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.