| Stroke is one of the major diseases that damage severely human health. With the advent of aging society, the incidence, mortality and disability rates of stroke are gradually the highest among all the diseases. Cerebral ischemia is the most common type of stroke. Thus, studies on pathogenesis, prevention and cure of cerebral ischemia are important topics to be solved urgently. Glutamate (Glu) is a major excitatory neurotransmitter in central nervous system, but over release of Glu may cause neuronal injury. A major pathway leading to neuronal injury during cerebral ischemia/reperfusion (I/R) involves elevation of extracellular Glu and activation of N-methyl-D-aspartate receptor, with a subsequent calcium overload, resulting in activation of nitric oxide synthsae (NOS) and overproduction of free radicals, nitic oxide(NO) and peroxynitrite anion (ONOO-). Therefore, it has been becoming the focus all over the world to investigate the injurious mechanisms and to develop neuroprotectant aiming at links of this injury pathway. Cholecystokinin (CCK), a typical brain-gut peptide as well as one of the most abundant neuropeptides in brain, is widely distributed in the central nervous system and gastrointestinal tract of both man and animals, and, as a neurotransmitter or modulator, is involved in variety of physiological and pathophysiological processes. CCK exists in various molecular forms, and the C-terminal sulfated octapeptide sequence (CCK-8), the minimum sequence for biological activity, is the major form in rodent brain. There are two distinct receptors for CCK, referred to as CCK-A receptor (CCK-AR) and CCK-B receptor (CCK-BR). Most CCK receptors in brain are of the CCK-B type, but CCK-A receptors occur in discrete brain regions. It has been found inrecent years that CCK has protective effects against many different injuries, such as I/R induced gastric lesions, seizure, neurotoxic effect of Glu, and central cholinergic neurons lesion, etc. There are few studies on the relationship between CCK and cerebral ischemia, and it still remains controversial about the neuroprotective effect of CCK or its receptor antagonist. As far as I know, there is no report yet about CCK alleviating focal cerebral ischemia (FCI)/reperfusion (FCI/R) injury by inhibiting injury pathway triggered by Glu. Changes in CCK receptor expression and CCK-8 levels in brain or plasma of rats subjected to FCI/R are also unclear. The purpose of this study is to evaluate the effect of intracerebroventricular (icv) injection with CCK-8 on FCI/R injury and the receptor mechanism from aspects of morphology, function and metabolism in rat FCI/R model produced by the intraluminal filament technique. The mechanisms by which CCK-8 exerts its action are also explored in vivo or in vitro by using methods of biochemistry, immunihistochemistry, molecular biology, and radioimmunoassay.1 CCK-8 attenuating FCI/R injury in rats1.1 Effect of CCK-8 on changes in brain morphology induced by FCI/R injuryTo observe the effect of CCK-8 or proglumide (Pro), a nonselective CCK receptors antagonist, on brain morphological changes or brain infarct size, male Sprague-Dawley rats (250g~290g body weight) were anesthetized by 10% chloral hydrate (350 mg / kg, ip), and were subjected to FCI/R by the intraluminal filament (0.25 mm in diameter) technique. Mean artery blood pressure (MABP) and heart rate were monitored, and rectal temperature was maintained at 36.5°C~37.5°C during cerebral ischemia. All drugs or vehicle (artificial cerebrospinal fluid, ACSF) were injected intracerebroventricularly (5 μl volume) under anesthesia at a location 0.8 mm posterior to the bregma, 1.5 mm left of the sagittal line, 3.7 mm deep from the dorsal dura 15 min~20 min before onset of cerebral ischemia. The experiment groups were as following: Sham group; I/Rgroup; different doses of CCK-8(0.3μg,1.0μg,2.0μg,4.0μg)+I/R group; Pro(20μg) + I/R group; Pro(20μg) + CCK-8(1.0μg)+ I/R group. At 24 h after reperfusion following 1 h of FCI, rats were decapitated an...
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