Accumulation of amino acids and hydroxyl free radicals in brain and retina of gerbil after transient ischemia.

The mongolian gerbil was introduced as a stroke model because of its incomplete circle of Willis. Unilateral carotid ligation ischemia produced in such a fashion was not effective in all gerbils. We have selected gerbils by examination of the ocular fundus to study the level of amino acids and hydroxyl free radicals (OH0 formation of DHBA, dihydroxybenzoic acid, from salicylate) in gerbil cerebral ischemia. Only gerbils with absence of retinal blood after ligation were selected as sensitive. One group (sham operated) served as control. The other group was subjected to unilateral left carotid occlusion with a clip during 30 minutes and classified as sensitive and non sensitive. Sixty minutes after release of the clip, levels of aspartate, glutamate, GABA were quantified in left hippocampus and in left retina. Levels of 2,5 DHBA (2,5 dihydroxybenzoic acid) were quantified in left retina and in left hemisphere. Compared to sham operated group, levels of aspartate (greater than 371%), glutamate (greater than 318%), GABA (greater than 122%) and 2,5 DHBA (greater than 385%) significantly increased in the group subjected to carotid occlusion. The determination of concentrations of amino acids and 2,5 DHBA in sensitive gerbils was a suitable method to study cerebral and retinal ischemia.

The auditory evoked potentials of gerbils after temporary occlusion of the left carotid artery.

This study examined brain-stem auditory evoked potentials response (BAEP) changes in the gerbil after temporary occlusion of the left carotid artery. Fourteen adult gerbils were subjected to unilateral left carotid ligation for 30 min. BAEPs were registered before and 5 min after occlusion, then 5 min, 60 min, 120 min, 24 h, 7 days and 28 days after release of the clip. Waves I (cochlear nerve), III (superior olivary complex) and V (inferior colliculus) were examined. Results were analysed using paired Student's t-test. Transient ischaemia increased latencies of waves I, III and V and the changes were more severe 5 min after release of the clip. In the gerbil, BAEPs might be a suitable method to study cerebral ischaemia.

[Role of prostaglandins in the mechanism of action of indapamide]. / Rôle des prostaglandines dans le mecanisme d'action de l'indapamide.

The role of prostaglandins (PG) has been evoked in the mechanism of action of indapamide. Indeed, PG can act in the regulation of the blood pressure (BP) at different levels: vasodilatation, diuretic, natriuretic, antagonism of angiotensin II and vasopressin (VP), action on adrenergic system. To confirm this hypothesis, we studied the action of certain eicosanoids inhibitors on the antihypertensive action of indapamide in the SHR rat, anaesthetized with pentobarbital (40 mg/kg i.p.). Indapamide (3 mg/kg i.p.) induces significant decrease on BP over 60 min. Mepacrine (5 mg/kg i.p.), phospholipase A2 inhibitor, indomethacin (5 mg/kg i.p), cyclo-oxygenase inhibitor, and tranylcypromine (0,1 mg/kg i.p.), prostacyclin synthase inhibitor, antagonize the antihypertensive action of indapamide. In order to eliminate the importance of VP, we used Brattleboro rats (genetically depleted in VP): indapamide (3 mg/kg i.p.) maintains its hypotensive activity. To eliminate the role of kidney in PG synthesis, we have used cyclo-oxygenase extrarenal inhibitor (sulindac) and the bilateral nephrectomy. Sulindac (1,25 mg/kg i.p.) and the bilateral nephrectomy do not remove the hypotensive action of indapamide. These results, demonstrating the PG extrarenal role and probably that of PGI2, localized in the vascular wall, could explain part of the antihypertensive mechanism of indapamide.