C. Imperatore

Time-course of blood-brain barrier permeability changes after experimental subarachnoid haemorrhage.

Summary¶ An increase in blood-brain barrier (BBB) permeability after subarachnoid haemorrhage (SAH) has been described in humans and has been correlated with delayed cerebral ischemia and poor clinical outcome. Few studies examined in the laboratory the relationship between SAH and BBB, with contrasting results due to limitations in experimental probes adopted and in timing of observation. The aim of this study was to quantify the time-course of BBB changes after experimental SAH. Groups of eight rats received injections of 400 μl of autologous arterial blood into the cisterna magna. BBB was assessed 6, 12, 24, 36, 48, 60, and 72 hours after SAH and in sham-operated animals separately for cerebral cortex, i.e. frontal, temporal, parietal, occipital, subcortical gray matter (Caudate-Putamen-Thalamus), cerebellar cortex and nuclei, and brain stem by a spectrophotofluorimetric evaluation of Evans Blue dye extravasation. As compared to sham-operated controls, SAH determined a significant BBB permeability change beginning 36 hours after SAH, peaking at 48 hours, and normalizing on day 3. This study provides a quantitative description of the temporal progression and recovery of BBB dysfunction after SAH. These results have implications for the management of aneurysm patients and for assessing the rationale and the therapeutic window of new pharmacological approaches.

Ageing influences haloperidol-induced changes in the permeability of the blood-brain barrier in the rat

Abstract— The effect of the dopaminergic antagonist haloperidol on the permeability of the blood‐brain barier (BBB) to [14C]α‐aminoisobutyric acid was studied in 10–12‐ and 28–30‐week old rats. Following the intraperitoneal injection of haloperidol (1 mg kg−1), an increase in the permeability of the BBB, with respect to younger animals, was observed within the occipital cortex, striatum, hippocampus and hypothalamus in the older rats. No correlation was found between haloperidol‐induced changes and age‐related differences in the permeability of the BBB. Such age‐associated increase in the vulnerability of the BBB when challenged with haloperidol might be related to a deterioration of the dopaminergic control of cerebrovascular permeability.

Modifications in the metabolic pathways of benzene in streptozotocin-induced diabetic rat.

Abstract Benzene is a ubiquitous environmental pollutant primarily metabolized by a cytochrome P-450 (CYP-450) isoenzyme, CYP-450 IIE1. A consistent induction of CYP450 IIE1 has been observed in both rat and human affected by diabetes mellitus. The aim of this study was to evaluate whether streptozotocin (STZ)-induced diabetes determines modifications in the metabolic pathways of benzene in rat. Benzene (100 mg/kg per day, dissolved in corn oil) was administered i.p. once a day for 5 days. Urine samples were collected every day in STZ-treated and normoglycaemic animals, treated and untreated with benzene (n = 10). Urinary levels of trans,trans-muconic acid and of phenol, catechol and hydroquinone (free and conjugated with sulphuryl and glucuronic group) were measured by high-performance liquid chromatography (HPLC). In normoglycaemic rats during the 5 days of treatment with benzene we observed a progressive and significant decrement in the urinary excretion of phenol, phenyl sulphate and glucuronide, catechol, catechol glucuronide, hydroquinone, hydroquinone glucuronide and t,t-muconic acid (P < 0.05). In the diabetic animals, conversely, the same metabolites showed progressively increasing urinary levels (P < 0.05). Catechol sulphate and hydroquinone sulphate levels were below the instruments detection limit. In the comparison between diabetic and normoglycaemic benzene treated rats, the inter-group difference was significant (P < 0.05) from day 3 of treatment for t,t-muconic acid, and from day 1 for free and conjugated phenol, free and glucuronide catechol and free hydroquinone. In the normoglycaemic rat exposed to benzene the decreasing trend observed in urinary excretion of free and conjugated metabolites may be due to their capability to reduce cytochromial activity. Conversely, in the diabetic rat, urinary levels of benzene metabolites tended to increase progressively, probably due to the consistent induction of CYP-450 IIE1 observed in diabetes, which would overwhelm the inhibition of this isoenzyme caused by phenolic metabolites. Furthermore, the metabolic switch towards detoxification metabolites observed after administration of high doses of benzene is not allowed in the diabetic because of reduced glutathione-S-transferase activity. As a consequence, higher levels of hydroquinone, phenol and catechol, considered the actual metabolites responsibles for benzene toxicity, will accumulate in the diabetic rat. Extrapolating these data to human, we may thus suggest that occupational exposure to benzene of a diabetic subject poses a higher risk level, as his metabolism tends to produce and accumulate higher levels of reactive benzene catabolites.

Effects of fructose-1,6-bisphosphate on brain polyamine biosynthesis in a model of transient cerebral ischemia

We evaluated the effects on cerebral ischemia of a treatment with fructose-1,6-bisphosphate, a compound known to possess protective effects on acute ischemic injury in a variety of different tissues. We investigated the ability of the compound, administered either 15 minutes before or 15 minutes after the ischemic insult, in reducing the ischemia-induced changes in polyamine brain levels. The experiments were performed in adult, chloral hydrate-anesthetized Mongolian gerbils that underwent a 15 minutes ligation of the common carotid arteries followed by recirculation. Animals were sacrificed 1, 8 and 24 hours and immediately after the release of the occlusion. Polyamine brain levels were not modified during ischemia. Putrescine began to increase after eight hours from the release of the occlusion and we found it significantly increased after 24 hours in the hippocampus and striatum. We did not detect any significant changes in spermidine brain levels either during ischemia or during recirculation. Conversely, spermine appeared to decrease in the hippocampus while it did not show changes in striatum and medulla-pons. The activity of ornithine decarboxylase, a key enzyme in the biosynthesis of polyamines, resulted enhanced at the end of the ischemic period in all the brain regions tested and showed a peak at eight hours of recirculation in striatum and hippocampus whereas returned to control values in the medulla-pons. Fructose-1,6-bisphosphate significantly reduced the ischemia induced changes in polyamine brain content when administered before the ischemic insult while did not show protective properties when administered post-ischemically.

Increased Cardiovascular Responsiveness to Central Cholinergic Stimulation in the Genetically Epilepsy-prone Rat

Abstract— We sought to determine whether differences in cardiovascular responsiveness to central stimulation of the cholinergic system existed between the genetically epilepsy‐prone and outbred Sprague‐Dawley rats. We treated the unanaesthetized, restrained rats with the indirect cholinergic agonist physostigmine (25, 50, 100 and 200 μg kg−1, i.v.) and the direct muscarinic agonist arecoline (50, 100 and 200 μg kg−1, i.v.). Blood pressure and heart rate were evaluated. Genetically epilepsy‐prone rats demonstrated to be more susceptible to the action of physostigmine than the outbred Sprague‐Dawley rats. Conversely, we did not note any difference between the two strains in the extent of the pressor response induced by arecoline. Moreover, we treated both strains with hemicholinium‐3 (34·8 nmol, i.c.v.) to deplete endogenous stores of acetylcholine. This treatment did not affect the pressor response to arecoline, whereas it greatly reduced the response to physostigmine. The present results support an increased cardiovascular responsiveness to central cholinergic stimulation in the genetically epilepsy‐prone rat which appears to be related to a pre‐synaptic rather than a post‐synaptic component.

Interaction between Pefloxacin and Aminophylline in Genetically Epilepsy‐prone Rats

The effects of a chronic treatment with pefloxacin on aminophylline‐induced seizures in genetically epilepsyprone rat have been investigated. Two series of experiments were performed. In the first, animals received pefloxacin orally twice a day for five days, then were administered aminophylline intraperitoneally and the occurrence of seizures was evaluated. In the second series of experiments, theophylline serum concentration was evaluated in rats subject to the same experimental protocol.