Abdeslam Chagraoui

New investigations within the TeO2-WO3 system: phase equilibrium diagram and glass crystallization

The TeO2-WO3 pseudo-binary system was investigated by temperature programmed X-ray diffraction and differential scanning calorimetry (DSC). The investigated samples were prepared by air quenching of totally or partially melted mixes of TeO2 and WO3. Glass forming compositions were identified by X-ray diffraction on quenched samples. Glass transition and crystallization temperatures were measured by DSC. The identification of the compounds appearing during glass crystallization revealed two new metastable compounds. The first one, which appears both for low WO3 content and pure TeO2 glasses, was attributed unambiguously to a new TeO2 polymorph called γ. This one irreversibly transforms into the stable α-TeO2 form, at about 510 °C. It crystallizes with the orthorhombic symmetry and unit cell parameters a = 0.8453(3) nm, b = 0.4994(2) nm, c = 0.4302(2) nm, Z = 4. The second compound was detected for samples containing about 5 to 10 WO3 mol %. It is cubic (F mode, a = 0.569 nm, Z = 4) and seems to have a fluorite-like structure. In addition, phase equilibrium diagram was determined. This binary system appears to be a true binary eutectic one.

Climbing and stereotyped behaviours in mice require the stimulation of D-1 dopamine receptors

Apomorphine-induced climbing and sniffing behaviours in mice were antagonize by low doses of SCH 23390 and metoclopramide. The selective D-2 dopamine receptor agonists, LY 171555 and RU 24926, and some other dopamine agonists (piribedil, lergotrile, bromocriptine) exerted only inhibitory effects on spontaneous behaviours. The selective D-1 dopamine receptor agonist, SK&F 38393, did not modify the climbing score but increased the sniffing and decreased the gnawing scores compared to the scores of control mice. Typical climbing and stereotyped behaviours were produced by the combination of SK&F 39383 with LY 171555, RU 24926 or with the other dopamine agonists tested. These data suggest that the stimulation of D-1 dopamine receptors is required for the induction of climbing and stereotyped behaviours in mice.

Effects of chronic treatments with amineptine and despiramine on motor responses involving dopaminergic systems

The acute effects of increasing doses of the antidepressant drugs amineptine (5–40 mg/kg, IP) and desipramine (5–20 mg/kg IP) were studied in mice on three parameters of the activity (the horizontal activity, the vertical activity and the number of small movements without displacement) measured in a computerized Digiscan actimeter. The horizontal and vertical activities were dose dependently and similarly increased by acute amineptine, whereas the number of movements without displacement was increased up to 10 mg/kg with no further significant modification up to 40 mg/kg; in contrast, all three parameters were reduced in an identical manner by desipramine. The changes in the responses to the selective D-1 dopamine (DA) receptor agonist SK&F 38393 (1.87–30 mg/kg, SC), to the selective D-2 DA receptor agonist LY 171555 (0.1–1.6 mg/kg, SC) and to the selective DA uptake inhibitor GBR 12783 (1.25–20 mg/kg, IP) were measured on the three parameters of activity in mice chronically treated with amineptine (20 mg/kg, IP twice daily during 15 days) or by desipramine (10 mg/kg, IP, twice daily during 15 days). The chronic treatments with amineptine or desipramine did not modify the motor stimulant effects GBR 12783 and of SK&F 38393 on the three parameters (excepted for a slight modification of the horizontal activity for 7.5 mg/kg SK&F 38393 in mice chronically treated with amineptine). In contrast, the motor inhibitory effects of the lowest doses of LY 171555 (0.1–0.4 mg/kg) were strongly reduced in mice chronically treated with amineptine or desipramine but only on the horizontal activity with no change on the vertical activity and on the number of small movements without displacement. These data indicate that, as in chronic treatment with typical antidepressant drugs like desipramine, chronic treatment with amineptine alters selectively the sedative effects induced by stimulation of D-2 DA autoreceptors in the mesolimbic dopaminergic area involved in the horizontal (locomotor) activity.

The rise of body temperature induced by the stimulation of dopamine D1 receptors is increased in acutely reserpinized mice

In naive mice, the selective D1 agonist, SK&F 38393 (7.5-30 mg/kg s.c.), induced a significant rise of body temperature (0.5-1 degree C) which was antagonized by SCH 23390 (100 micrograms/kg s.c.) and by flupenthixol (0.4 mg/kg i.p.). In mice treated with reserpine (5 mg/kg s.c.) 18 h before testing, which on its own caused intense hypothermia (10-12 degrees C), SK&F 38393 (1.87-30 mg/kg s.c.) induced a dose-dependent and more marked rise of body temperature (5-7 degrees C). Similarly, SK&F 38393 (30 mg/kg s.c.) partially prevented reserpine-induced hypothermia. The central origin of the SK&F 38393 effects in reserpine-treated mice is indicated by the rise of body temperature induced by the i.c.v. administration of the drug (12.5-50 micrograms per mice). The SK&F 38393-induced rise of body temperature in acutely reserpinized mice was antagonized by SCH 23390 (50-200 micrograms/kg s.c.), clozapine (1.87-30 mg/kg i.p.) or chlorpromazine (2-32 mg/kg i.p.) but not by metoclopramide (25 or 100 mg/kg i.p.) or amisulpride (12.5 or 50 mg/kg). In naive mice, apomorphine (1 mg/kg s.c.) or LY 171555 (0.4 mg/kg s.c.) induced hypothermia which was antagonized by amisulpride (12.5 mg/kg i.p.); a transiently increased body temperature was even measured 30 min after apomorphine injection in amisulpride-treated mice. Apomorphine (1 mg/kg s.c.) induced a rise of body temperature in acutely reserpinized mice which was significantly reduced by SCH 23390 (50 and 200 micrograms/kg s.c.) and significantly increased by amisulpride (12.5 and 50 mg/kg i.p.). These data suggest that pharmacologically different dopamine receptor subtypes mediate different effects on body temperature in mice: D1 dopamine receptors mediate a rise of body temperature which is increased in hypothermic reserpinized animals and dopamine receptors of the D4 subtype mediate the decrease of body temperature in naive mice.

The Bi2WO6-TeO2 pseudo binary system

Summary The phase diagram of the Bi 2 WO 6 -TeO 2 pseudo-binary system has been established from 60 to 100 TeO 2 mol %, using DSC and XRD experiments. Three fixed temperature events were found: one eutectic and two peritectics. The new compounds Bi 2 Te 2 WO 10 and Bi 2 Te 5 WO 16 were identified and characterized by X-ray diffraction.