Effect of curcumin on morphine-induced antinociception in acute corneal pain in rats

In the present study, the effects of the acute and chronic oral administrations [po] of curcumin in the absence and presence of morphine and naloxone was investigated on the sensation of acute corneal pain in rats. Acute corneal pain was induced by the local application of hypertonic saline [5 M NaCl] on the corneal surface, and the number of eye wipes was then counted for 30 s. Subcutaneous [sc] injections of morphine [1, 2 and 4 mg/kg] significantly suppressed corneal pain [p<0.05]. Naloxone [2 mg/kg, sc] did not change the intensity of pain when used alone, but pretreatment of the rates with naloxone [2 mg/kg, sc] significantly prevented the antinociceptive effect induced by morphine [2 mg/kg, sc; p<0.05]. The short-term and long-term oral administration of curcumin [either a single dose of 200 mg/kg or dosages of 6.25, 12.5 of 25 mg/kg for 15 days each, respectively] both significantly decreased the number of eye wipes [p<0.05]. The antinociceptive effect induced by morphine was significantly [p<0.05] enhanced by both the acute [200 mg/kg, once, po] and chronic [25 mg/kg, 15 days, po] curcumin treatments. Naloxone [2 mg/kg, sc] did not change the antinociception that was induced by acute [200 mg/kg, once, po] and chronic [25 mg/kg, 15 days, po] treatments of curcumin. The present findings suggest that morphine produced an analgesic effect through a naloxone-sensitive mechanism in acute corneal pain. Both high-dose acute and lower-dose chronic oral administrations of curcumin suppressed corneal pain. Moreover, curcumin enhanced morphine-induced antinociception

Effect of blood glucose level changes on the formalin-induced pain in mice

The effect of blood glucose level changes induced by 24h food deprivation and intraperitoneal [IP] injection of insulin [2IU/kg] and glucose [2gr/kg] was investigated on the pain induced by intraplantar [IPL] injection of formalin [20 micro l, 5%] in mice. Blood glucose level changes were determined by blood sampling from the apex of the tail of mice. IPinjection of insulin and 24h food deprivation decreased and IP injection of glucose increased the blood glucose level. IPL injection of formalin produced a marked biphasic pain response with a quiescent phase between them. Insulin and food deprivation reduced the late [inflammatory] phase of pain. Exogenous glucose increased the quiescent phase of formalin pain. It seems that hypoglycemia and hyperglycemia may not have a role in neurogenic pain. Hypoglycemia reduces the inflammatory pain. Hyperglycemia produces hyperalgesia by increasing the pain response in the quiescent phase

effect of intraperitoneal injection of histidine on defecation rate in rabbits

Histidine at the doses 30 and 60ml /kg had no effect when injected at 7 :OOh, or at 19:00h. Histidine at the doses of 120, 240 and 480 mg/kg decreased defecation at the first 8 and 24 hours post injection, respectively, when injected at 07:00h. The amino acid at the doses of 120, 240 and 480 mg/kg decreased the number of fecal pellets at 2, 8 and 24 h post injection, respectively, when injected at 19:00h. Suppressive effect of histidine in the light period was more intense and lasted longer than that in the dark period. The mean number of pellets for each individual prior to the interventional study was recorded as interval negative control

Body temperature of sheep following intracerebroventricular injections of prostaglandins E[2]and F[2]alpha

The effect of intracerebroventricular injections of prostaglandins E[2] and F[2]alpha was studied on the rectal temperature of sheep. PGE[2] but not PGF[2]alpha at the same dose of 50microg elevated the 1h post-injection of rectal temperature. PGE[2] but not PGF[2] alpha at the same dose of 100microg increased 3.5 and 2h post- injection of rectal temperature, respectively. Elavation of rectal temperature following PGE[2] and PGF[2]alpha injections at the same dose of 200microg lasted to 5 and 3h after injection, respectively. Significant differences between PGE[2] and PGF[2]alpha at the doses of 100 and 200 microg observed from 2[nd] and 3[rd] h after injection. It is concluded that prostaglandins E[2] and F[2]alpha increase the body temperature but the hyperthermic effect of PGE[2] is stronger and longer than that of PGF[2]alpha

Light / dark changes of feeding, drinking and defecation in laboratory rabbits

To investigate the 12h: 12h light / dark changesof feeding, drinking and defecation in laboratory rabbits . Experimental study. Ten male New Zealand white rabbits weighing2.5-3kg. Rabbits were individually maintained instandard cages [45 45 60cm] in a laboratory undercontrolled temperature [20 - 23°C] and 12/12h light - darkcycles for induction of adaptation. They were fed with acommercial pelleted diet and water twice daily [7.00 and19.00h]. Fecal pellets and consumed food and water weremeasured every 4h for 10 consecutive days . The rates andratios of the above mentioned parameters were calculatedat 12h light, 12h dark and total 24h periods. Repeated measures ANOVA andDuncan test. Maximal rates of food and water intake wereobtained at 19-23 and 23-3h time intervals. Their minimalrates were occurred at 3-7h time interval. Defecation, withminimal rates at 7-11 and ll-15h time intervals, showedmaximal rates at 15-19, 19-23 and 23-3h time intervals.Food, water intake and defecation rates at 12h dark periodwere higher than that of 12h light period. The 12h dark /total 24h ratios of the parameters were higher than that of12h light / total 24h ratios, too. From the results of this study it isconcluded that laboratory rabbits perform more of feeding,drinking and defecation activities from the beginning tomiddle hours of dark period. From this point of view,rabbits belong to the nocturnal animals group

Effect of intracerebroventricular injection of histamine HI and H2 antagonists on food intake in freely feeding and food-deprived rabbits

To investigate the role of central histamine HI and H2 receptors on food intake in freely feeding and food - deprived rabbits. Experimental study. Forty - two male New Zealand white rabbits weighing between 2.5 - 3 Kg. A 23- gauge, 18mm long stainless steel guide cannula was surgically implanted into the lateral ventricle of brain. Intracerebroventricular injections of normal saline [control], promethazine and ranitidine at the same doses of 50, 100 and 200 microg /rabbit in a volume of 5 microl were performed using a 25 micro1 Hamilton's syringe. Cumulative food intake was measured in freely feeding and food - deprived rabbits at the 0.5, 1, 2, 3, 6 and 24h after injections. Paired t-test, Factorial ANOVA and Duncan's test. Food deprivation for 16h increased 0.5,1,2, 3 and 6h cumulative food intake. In freely feeding rabbits, promethazine [50 microg] had no effect on food intake, and at the dose of 100 microag increased 1 and 2h feeding after injection, but at the dose of 200 microag increased 2 and 3h post-injection food intake. In the 16h food- deprived rabbits promethazine [50,100 and 200 microg] had no effect. Ranitidine at the doses of 50,100 and 200 microg produced no significant changes on food intake in both freely feeding and food- deprived rabbits. Promethazine did not exert any significant effects on the 6 and 24h post- injection food intake. Based on the results of the present study it is concluded that the blockade of central HI but not H2 receptors induce a short- lasting excitatory effect on food intake. Thus, central HI receptor may have an important role in the central control of feeding behavior

[Effect of chlorpheniramine on formalin-induced pain in mice: its relation with opioid system]

To investigate the effect of intraperitoneal injection of chlorpheniramine on formalin - induced pain and morphine analgesia. Experimental study.Seventy - two male mice weighing between 23-26 gr.Animals were placed in the formalin test chambers. Intraplantar injection of formalin [201, 5%] with a 28-guage injection needle was performed. The durations of the licking and biting of the injected paw was measured every five min for Ih. Intraperitoneal injections of chlorpheniramine at doses of 5, 10 and 20 mg/kg, morphine [5 mg/kg] and subcutaneous injection of naloxone [5 mg/kg] were performed. Furthermore, Chlorpheniramine was also injected [i.p., 20 mg/kg] after morphine [i.p., 5 mg/kg] and before naloxone [s.c., 5 mg/kg].One - way and repeated measures ANOVA and Duncan test.Intrapaw injection of normal saline induced a weak response only in the first five min. Formalin injection by the same route produced a biphasic pain response [first phase: 0-5 and second phase: 20-40 min after injection]. Intraperitoneal injection of chlorpheniramine [5, 10 and 20 mg/kg] without any effect on first phase, suppressed the second phase of pain. Morphine [i.p. 5mg/Kg] produced analgesia by reducing both phases of pain. Naloxone [s.c., 5mg/kg] did not change the formalin - induced pain. Chlorpheniramine injection after morphine potentiated the morphine analgesia, but it's injection before naloxone did not prevent the naloxone - induced hyperalgesia. Based on the present results it is concluded that chlorpheniramine [HI antagonist] produced antinociception in the second phase [inflammatory phase] of formalin - induced pain. Hence, HI receptors may have a role in inflammatory pain. In this regard, antnociception induced by a HI antagonist may be dependent on opioid system