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Biomedical subjects

P Rossignol

Publications and source records attributed to P Rossignol.

At least 37 records · Page 2Linked to original sources
PubMed1987

Liposomally-entrapped ATP: improved efficiency against experimental brain ischemia in the rat.

ATP was entrapped inside negatively charged liposomes composed of sulfatide, in order to improve its penetration into the brain and to reduce its degradation into other tissues. These liposomes were prepared according to an original method allowing a satisfying stability of the formulation. Liposomally entrapped ATP was administered intracerebroventricularly to rats submitted to brain ischemic episodes by both carotid artery clamping and systemic blood pressure lowering (during 3 minutes every 15 minutes). Such treatment importantly increases the number of ischemic episodes before brain silence appeared. So, this paper allows new perspectives in the administration of drugs into the brain.

Adenosine Triphosphate↗
PubMed1987

Stereoselectivity of the inhibiting effects of baclofen on the electrogenesis of the rat cortex under ischemia.

Gamma-aminobutyric acid and dl-baclofen decrease the resistance against ischemia appraised by the number of ischemic episodes tolerated before electrocorticographic silence or cardiac arrest. D-enantiomer of baclofen does not exhibit this deleterious result in high doses either; it even counteracts the effect of its racemate and that of GABA. These data suggest that, in the brain, GABA and baclofen act at the same GABA-B receptor. This is in contrast to the existence of two distinct receptors demonstrated for the antinociceptive effects on the spinal cord.

Animals↗
PubMed1986

Extracorporeal cephalic blood autoperfusion method in the rat. Hemorrheological evaluation and proposed pharmacological uses.

We propose a constant cephalic blood perfusion method especially suitable to the rat. Cerebrovascular blood pressure is artificially regulated by an extracorporeal circuit with a perfusion pump and a Starling valve. A hemorrheological evaluation allows one to demonstrate an extracorporeal circuit that shows a growing pathological evolution, which can be purposely accelerated by iterative ischemic episodes. This method can be used (as shown by some examples) as a model for cerebrovascular failure or to study deleterious effects of the extracorporeal circuit.

Animals↗
PubMed1984

Effects of procaine on the oxidative phosphorylation of brain mitochondria from senescent rats.

Senescence affects cerebral metabolic functions. Various drugs have been tested to counteract the effects of aging on the brain. In this paper, we studied the influence of treatment using procaine, 1 mg per 100 g body weight, injected over a period of 3 days, to both young and old rats, on the phosphorylative oxidation properties of cerebral mitochondria. Respiratory activity decreased significantly in the brain of old rats. This reduction of oxygen consumption measured in the presence of glutamate, reached 31% in state 4, 25% in state 3 and, in the presence of succinate, 23% in state 4 without significant changes in state 3. The injection of procaine into young rats induced a significant increase of oxygen consumption rate with both glutamate and succinate as substrates. The same treatment administered to old rats was followed by a rise in respiratory activity, with values close to those observed in young control rats. Although the mechanism of action of procaine is not yet clear, there is some evidence that it interacts with membrane phospholipid sites. Therefore, it may be concluded that procaine facilitates oxygen transport towards the mitochondrial matrix by modifying the membrane structure in both old and young rats, although, in the latter case, this increase is not intended to improve the energetic properties of the mitochondrion.

Aging↗
PubMed1984

Highly selective photoaffinity labeling of mu and delta opioid receptors.

We report the synthesis and photolabeling properties of two highly selective ligands for mu and delta opioid-binding sites: Tyr-D-Ala-Gly-MePhe (pN3)-Gly-ol (AZ-DAMGE) and Tyr-D-Thr-Gly-Phe (pN3)-Leu-Thr (AZ-DTLET). An irreversible inhibition of the electrically induced contractions of mouse vas deferens is caused by irradiation (at 254 nm) of the muscle strip in the presence of AZ-DTLET (1 nM). This phenomenon is antagonized only at large concentrations (10 microM) of naloxone, in accordance with the well-known lower selectivity of naloxone for delta sites. Competition experiments with [3H]DAMGE and [3H]DTLET on crude rat brain membranes showed that the azido photoprobes display a similar (AZ-DAMGE) and even a better (AZ-DTLET) selectivity than their respective parent compounds DAMGE and DTLET. Up to 25 nM, AZ-DTLET irreversibly and selectively photolabels the delta sites of crude rat brain homogenates. Due to its lower affinity AZ-DAMGE provides similar selective photolabeling of the mu sites but at higher concentrations (approximately equal to 0.3 microM). When [3H]DAMGE and [3H]DTLET were used as ligands for mu and delta binding subtypes, respectively, no important change in binding capacity and affinity of one receptor type was observed after photolabeling of the other.

Affinity Labels↗
PubMed1983

Deltakephalin, Tyr-D-Thr-Gly-Phe-Leu-Thr: a new highly potent and fully specific agonist for opiate delta-receptors.

Deltakephalin, Tyr-D-Thr-Gly-Phe-Leu-Thr (DTLET) was rationally designed as pure delta-probe from proposed models of mu and delta opiate receptors. On peripheral organs, deltakephalin displays a 3000 times higher inhibitory potency on the electrically stimulated mouse vas deferens (IC50 = 0.15 nM) as on the guinea pig ileum (IC50 = 460 nM). As expected [3H]deltakephalin interacts at 35 degrees C in rat brain tissue to a single class of binding sites (delta) (Bmax = 0.115 pmole/mg protein) with a high affinity: KD = 1.35 nM from equilibrium measurements and KD = 0.43 nM from kinetic determinations. Deltakephalin occurs as the most specific ligand for delta-binding sites as shown by the following discrimination ratios KI(mu)/KI(delta): 0.31 for D-Ala2-D-Leu5-enkephalin; 0.15 for D-Ser2-Thr6-Leu-enkephalin and 0.05 for deltakephalin.

Animals↗
PubMed1982

[Protective effects of muscimol on acute brain ischemia in the rat (author's transl)].

Rats given i.c.v. muscimol overcome a greater number of hypoxic episodes before dying compared with controls whereas animals that receive baclofen (another GABAergic agonist) or GABA itself tolerate fewer episodes than controls. Thus, chloride ions ionophoric site activation appears to be necessary in order to obtain any GABAergic antihypoxic protection whereas GABAergic site activated by both baclofen and GABA would induce an opposite effect.

Animals↗
PubMed1977

[Increase in the oxygen available to the cerebral cortex after the administration of carbonic anhydrase inhibitors].

Oxygen tension (pO2) in cerebral cortex was measured by polarographic method in unanesthetized rabbits. Intravenous administration (25 mg/kg) of carbonic anhydrase inhibitors (acetazolamide, methazolamide, dichlorphenamide, sulthiame) induced an early important rise of cortical p O2, which is not dependent on increase of p O2 and p CO2 and decrease of pH in arterial blood. High dosage of acetazolamide (250 mg/kg) produced the same effect and did not suppress the increase of cortical p O2 under air-CO2 inhalation. This result suggests that CO2 might act specifically upon cerebral vessels.

Animals↗