Neuroprotective effects of Ginkgo biloba extract in brain ischemia are mediated by inhibition of nitric oxide synthesis.

We studied the effects of pre-treatment (15 days) with oral administration of Ginkgo biloba extract (Ph-Gb 37.5-150 mg/kg) on brain malonildialdehyde (MDA), brain edema, brain nitrite and nitrate and delayed neuronal death following transient cerebral ischemia in the Mongolian gerbil. Survival was not modified, however, pre-treatment with Ginkgo biloba significantly and in a dose-dependent way reduced post-ischemic brain MDA levels and post-ischemic brain edema. Delayed neuronal death in the CA1 of the hippocampus was attenuated by the highest dose of the extract. Increase of nitrite and nitrate was observed after cerebral ischemia in the hippocampus and it was dose-dependently reduced in animals pretreated with Ph-Gb, thus suggesting that neuroprotective effects of Ginkgo biloba may be due to an inhibitory action on nitric oxide formation.

Erythropoietin protects against brain ischemic injury by inhibition of nitric oxide formation.

Erythropoietin prevents in vitro glutamate-induced neuronal death and could play a role in the central nervous system. We investigated the in vivo effects of recombinant human erythropoietin after intraperitoneal (i.p.; 25-100 U) or intracerebroventricular (i.c.v.; 0.25-25 U) administration on survival, brain malonildialdehyde (MDA) levels, brain edema, hippocampal neuronal death and brain nitric oxide (NO) synthesis after bilateral carotid occlusion (5 min), followed by reperfusion in the Mongolian gerbil. Peripheral posttreatment with recombinant human erythropoietin reduced postischemic MDA levels, brain edema and increased survival. Either peripheral or i.c.v. posttreatment with recombinant human erythropoietin significantly reduced hippocampal CA1 neuronal loss, observed 7 days after the ischemic event. Increase of nitrite and nitrate (as an index of NO formation) in the hippocampus, as observed after ischemia, was reduced in animals treated with recombinant human erythropoietin. These data suggest that in vivo recombinant human erythropoietin effects on brain ischemic injury could be due to inhibition of NO overproduction.

Effects of water deprivation and angiotensin II intracerebroventricular administration on brain nitric oxide synthase activity.

Intracranial administration of L-arginine causes a reduction of the water intake induced by water deprivation or by intracerebroventricular (i.c.v.) injection of angiotensin II (angiotensin II), through the release of nitric oxide (NO) in the central nervous system. We studied the effects of i.c.v. angiotensin II (120 ng/rat) in association with i.c.v. L-arginine (2.5-10 microg/rat) on blood pressure. We also studied the effects of both peripheral and central angiotensin II injection (1.5-6 mg kg(-1) i.p. and 30-120 ng rat(-1) i.c.v., respectively) on NO synthase activity in the cortex, diencephalon and brainstem, after water deprivation (24 h), conditions producing activation of the renin-angiotensin system. L-arginine dose dependently antagonized the increase in blood pressure induced by i.c.v. angiotensin II (P < 0.001). Peripheral administration of angiotensin II produced a dose-dependent reduction of NO synthase activity in the brainstem and cortex (P < 0.001), but not in the diencephalon. Water deprivation produced similar effects on brain NO synthase activity. Angiotensin II i.c.v. injection caused NO synthase activity reduction in all brain regions studied (P < 0.001). Our findings suggest that NO and angiotensin II could play opposite roles in brain regulation of blood pressure and drinking behaviour.

Effects of interleukin-10 on water intake, locomotory activity, and rectal temperature in rat treated with endotoxin.

Intracerebroventricular (i.c.v.) interleukin-10 (25, 50, and 100 ng/rat) effects on water intake, exploratory behaviour, and rectal temperature were evaluated in rats treated intraperitoneally (i.p.) with lipopolysaccharide (0.32, 0.64, and 0.96 mg/kg). Endotoxin administration induced fever and inhibition of thirst in water-deprived rats, and a decrease in lococomotory activity in normohydrated and water-deprived animals. Our data show that interleukin-10 during lipopolysaccharide administration controlled fever, increases exploratory behaviour, but did not reverse lipopolysaccharide inhibition of thirst. These effects suggest that fever, depression in locomotory activity but not inhibition of thirst, induced by endotoxin are influenced by interleukin-10 levels.

Interleukin-1 inhibits drinking behaviour through prostaglandins, but not by nitric oxide formation.

Interleukin-1 beta (IL-1 beta) causes inhibition of drinking behaviour. Moreover it induces formation of prostaglandins (PGs) and nitric oxide (NO). Both PGs and NO are able to inhibit drinking stimulated by water deprivation or by intracerebroventricular (i.c.v.) administration of angiotensin II. In this study, we studied in the preoptic area (POA) the possible role of PGs and NO in the antidipsogenic action induced by IL-1 beta. IL-1 beta was injected in the lateral cerebral ventricle (i.c.v.) (2.5, 10, 20, and 40 ng/rat) or into POA (0.625, 1.25, 2.5, and 10 ng/rat). L-arginine (12.5, 25, 50, and 100 ng/rat), the precursor of NO, or NG-nitro-L-arginine methyl ester (L-NAME) (25, 50, and 100 ng/rat), an inhibitor of nitric oxide synthase (NOS), were injected only into POA. Drinking behaviour was induced by water deprivation (24 h). IL-1 beta injected either i.c.v. or into POA caused dose dependent inhibition of drinking. In the POA a treatment with acetylsalicylic acid (ASA) (33, 66, and 135 micrograms/rat), but not with L-NAME, antagonized the inhibition of drinking behaviour induced by the highest doses of IL-1 beta in the POA. In the POA, a treatment with ASA or L-NAME antagonized the inhibition of drinking behaviour caused by injection of the highest doses of L-arginine. Our data suggest that the central inhibition of drinking behaviour of IL-1 beta is mediated through the formation of PGs, but not NO, in the POA.

Inhibition of nitric oxide formation reduces voluntary ethanol consumption in the rat.

Brain nitric oxide is involved in the mechanisms that regulate ingestive behavior. To test whether this compound plays a role in alcohol preference, we studied the effects of different doses of NG-nitro-L-arginine (L-NO arg), an inhibitor of nitric oxide synthase (NOS), on voluntary consumption of ethanol and on blood alcohol levels produced by a single intraperitoneal dose of alcohol in the rat. L-NO arg produced a significant and dose-dependent reduction of ethanol intake (P < 0.001) without influencing total fluid consumption or feeding behavior. L-NO arg did not influence the kinetics of alcohol. Our data show that inhibition of nitric oxide formation accompanies reduction of ethanol intake and suggest a possible role for nitric oxide in ethanol self-administration.

Multiple actions of the coumarine derivative cloricromene and its protective effects on ischemic brain injury.

The effects of different doses (0.25, 0.5, 1 and 2 mg/kg i.p.) of cloricromene, a coumarine derivative, have been investigated on brain malondialdehyde levels, brain edema, myeloperoxidase activity, survival, locomotor hyperactivity and hippocampal neuronal loss following transient cerebral ischemia induced by temporary bilateral carotid occlusion in the Mongolian gerbil. Cloricromene reduced brain lipid peroxidation, measured through the evaluation of malondialdehyde (-82.9% with the highest dose), and the formation of post-ischemic brain edema, evaluated by water content. The increase in myeloperoxidase activity observed in the hippocampus of postischemic animals was also reduced: 0.7 +/- 0.3 U x 10(-3) vs. 3.3 +/- 0.3 U x 10(-3)/g tissue. The same treatment increased survival and reduced hyperactivity linked to neurodegeneration induced by cerebral ischemia and reperfusion. Histological observations of the pyramidal layer of CA1 showed a reduction of neuronal loss in animals that received the drug before occlusion but not in those that were treated after the occlusion. These results show that cloricromene, a drug with multiple actions, improves brain injury induced by transient cerebral ischemia.

A new antioxidant drug limits brain damage induced by transient cerebral ischaemia.

Restoration of blood flow after an ischaemic event generates the formation of oxygen radicals which could augment brain damage. The authors studied the effects of different doses (50, 100, 200 mg/kg/i.p.) of a new antioxidant, IRFI-016, [2(2,3-dihydro-5-acetoxy-4,6,7-trimethylbenzofuranyl) acetic acid] on brain damage in the Mongolian gerbil induced by 5 min of bilateral carotid occlusion (BCO) followed by reperfusion. Post-ischaemic brain malondialdehyde (MDA) levels and locomotor activity at different times and delayed neuronal death of hippocampal CA1 area on the fourth day after occlusion were evaluated. During reperfusion, after BCO, enhancement of brain MDA occurs (37.5%, 62.5% and 100% at 15, 30 and 60 min of reperfusion, respectively). Brain MDA postischaemic increases were reduced at 15 min of reperfusion to 15.4% and 44.4% by IRFI-016, 100 and 200 mg/kg, respectively. After 30 min of reperfusion brain MDA was reduced to 31.25% and 53.13% by IRFI-016 100 and 200 mg/kg, respectively. Hyperactivity and delayed neuronal death of CA1 were significantly reduced in postischaemic gerbils treated with the highest doses of IRFI-016. Results indicate that pretreatment with the antioxidant IRFI-016 improves in a dose-dependent manner brain damage induced by ischaemia and reperfusion in the gerbil.

Cloricromene antagonizes antidipsogenic effects induced by endotoxin, but not by TNF alpha, in the rat.

Intravenous (640 micrograms/kg) or intracerebroventricular (0.5 and 1 microgram) injection of Escherichia coli endotoxin (LPS) causes inhibition of water intake induced by 24 hour period of water deprivation in the rat. Tumor necrosis factor alpha (TNF-alpha; 20 and 40 ng/rat) given into the lateral cerebral ventricle (i.c.v.) causes effects similar to those observed after LPS. Cloricromene, given either intravenously (1 and 2 mg/kg) or i.c.v. (250 and 500 ng), abolished the antidipsogenic effect induced by LPS (administered both i.v. and i.c.v.). Cloricromene (2 mg/kg, i.v. or 500 ng/rat, i.c.v.), on the contrary, did not modify the antidipsogenic effects induced by TNF-alpha. These data indicate that peripherally injected cloricromene (as well as that i.c.v. injected) antagonizes the effects of mediators of LPS on sites regulating thirst and suggest that cloricromene's action may be due to inhibition of brain TNF-alpha formation induced by LPS.