Magdi R.I. Soliman

The effects of estradiol and progesterone on pain sensitivity and brain opioid receptors in ovariectomized rats

Previous studies in our laboratory have shown that estradiol and progesterone affect beta-endorphin and Met-enkephalin levels in specific brain regions and that these effects are diurnally controlled. The present investigation was conducted to evaluate the effects of estradiol and progesterone on pain latency and brain opioid receptors of ovariectomized rats. Female Sprague-Dawley rats (100-120 g) adapted to a 12 hr light:12 hr dark illumination cycle were used in these studies. Animals were ovariectomized under pentobarbital anesthesia. After a recovery period of 10-14 days, estradiol (50 micrograms/kg/day in 0.2 ml olive oil) and progesterone (5 mg/kg/day in 0.1 ml olive oil) were administrated subcutaneously in the dorsal neck region alone and in combination at 16:00 hr for 7 days. Control animals received 0.2 ml olive oil. Control and treated groups were evaluated daily for pain latency postinjection using the tailflick and hotplate methods. On Day 7 of drug treatment, animals were sacrificed by decapitiation after pain latency evaluations. Whole brains were removed and immediately frozen at -70 degrees C. Binding and affinity of brain opiate receptors were determined for each treatment group. Results obtained indicate that estradiol and progesterone treatment alone or in combination significantly alter pain latency. This alteration in pain was not accompanied by any change in affinity or number of mu opioid receptors. However, an increase in Kd of kappa opiate receptors was observed following treatment with estradiol, progesterone, or their combination. This increase in Kd of kappa opiate receptors may in part explain the increased hotplate sensitivity following estrogen administration. The present findings suggest that the decrease in pain sensitivity induced by estradiol or progesterone could not be explained by their effects on opioid receptors. The previously reported effects of estradiol and progesterone on brain levels of beta-endorphin and Met-enkephalin may contribute to the analgesic effects of these steroids.

Protective effects of antioxidants against benomyl-induced lipid peroxidation and glutathione depletion in rats.

The present in vivo study was designed to examine the effects of the antioxidants, N,N-diphenyl-p-phenylenediamine (DPPD) and a 21-aminosteroid (U74389G), on methyl 1-(butylcarbamoyl)-2-benzimidazole-carbamate (benomyl)-induced lipid peroxidation and glutathione depletion in rats. Male Sprague Dawley rats weighing 200 250 g were used in this study and were fasted for 8 12 h before treatment. Benomyl (200 mg/kg/day in olive oil) was administered orally for 7 days to groups of untreated rats and to rats pretreated with two doses (15 mg/kg) of either DPPD or U74389G. Benomyl treatment resulted in a significant increase in serum hydroperoxides and a significant decline in hepatic reduced glutathione (GSH) levels. These results indicate that benomyl induces lipid peroxidation and glutathione depletion in rats. Benomyl-induced lipid peroxidation was blocked by DPPD pretreatment but was not significantly altered by U74389G. However, both antioxidants, DPPD and U74389G, were able to inhibit glutathione depletion induced by benomyl. The present findings indicate that the in vivo toxicity of benomyl may be associated with oxidative stress to cellular membranes and that some degree of protection against this toxicity could be afforded by antioxidants.

Effects of tacrine (THA) on spatial reference memory and cholinergic enzymes in specific rat brain regions

Cognitive function of rats treated with saline (control), THA (8 mg/kg, i.p.), scopolamine (5 mg/kg, i.p.), or a combination of THA (8 mg/kg) and scopolamine (5 mg/kg) was tested in the Morris water maze. The latency to find the platform in the water maze was used to evaluate performance. THA did not significantly alter the latency period as compared to control rats. Scopolamine resulted in a highly significant (p<0.01) increase in latency period (183% increase) as compared to saline treated controls. However, when THA was concurrently administered with scopolamine, it was able to completely reverse the performance decrement induced by scopolamine. Immediately following spatial reference memory testing, animals were sacrificed by decapitation one hour post injection. Brains were immediately removed and the cortex, hippocampus, hypothalamus, and pituitary were dissected and their choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activity were determined spectrophotometrically. THA administration resulted in a significant increase in ChAT activity in the cortex (23% increase). However, when THA was concurrently administered with scopolamine, a significant increase in ChAT activity was observed in cortex (77% increase), hippocampus (32% increase), hypothalamus (97% increase), and pituitary (92.5% increase). THA administration resulted in a significant decrease in AChE activity (p<0.001) in cortex (62% decrease), hippocampus (78% decrease), and hypothalamus (90% decrease). When tacrine was administered with scopolamine, a significant increase was found in the cortex (197% increase) and the hippocampus (207% increase). In conclusion, the increase in ChAT activity produced by tacrine may in part explain its ability to reverse the scopolamine induced decrease in spatial reference memory and may play a role in its beneficial effect in improving cognitive ability.

Intratracheal exposure of the guinea pig lung to cadmium and:or selenium: a histological evaluation

Anesthetized male Hartley guinea pigs (350-410 g) (n=5) received intratracheally, saline; cadmium (Cd) (0.3 mg); selenium (Se) (0.3 or 0.06 mg); or Cd (0.3 mg) with Se (0.06 mg), per animal. Twenty-four hours later, lungs were evaluated. Bronchoalveolar-lavage fluid of Cd- and/or Se-treated animals varied in their total and differential leukocyte percent population from that of saline control (P<0.05). Cadmium alone or with Se caused high lung to body weight ratios (P<0.05). High lung wet-weight to dry-weight (W/D) ratios (P<0.05) suggestive of lung edema, were evident after Cd and/or Se exposure. Histological examination of Cd- and/or Se-exposed lungs revealed leukocytic infiltration. Results demonstrated that separate or concurrent exposure to noxious metal(s) such as Cd and Se provoke lung edema and injury. Low dose of Se which when instilled alone, although did not result in an increased W/D lung ratio, failed to subside concurrently administered Cd-inflicted damage.

Testosterone Reverses Ethanol-Induced Deficit in Spatial Reference Memory in Castrated Rats

The present study was designed to evaluate the effects of ethanol, testosterone and combination of ethanol and testosterone, on spatial reference memory and β-endorphin (β-EN) levels in castrated rats. Male Sprague-Dawley rats (120–150 g) were used in this study, Animals were castrated and ethanol, testosterone or combination of the drugs were administered to rats at 09:00 h. The drugs were administered after a training period of 5 days and spatial reference memory was evaluated for 7 days using the Morris water maze. One hour after the last injection, animals were sacrificed, their brains removed and dissected into cortex, hypothalamus, hippocampus and midbrain. The β-EN levels in these brain regions were determined by radioimmunoassay. The time to find the platform (latency period) was significantly increased in ethanol-treated rats, indicating that ethanol induces deficit in spatial reference memory. On the other hand, testosterone administration improved spatial reference memory by significantly decreasing the latency period. In addition, there was a significant decrease in latency period in the animals treated with combination of ethanol and testosterone. Results also indicate that administration of ethanol resulted in a significant increase in β-EN levels in the hippocampus and in the cortex while concurrent administration with testosterone abolished this increase. These findings clearly indicate that administration of testosterone did not only improve memory but also abolished the spatial memory deficit induced by ethanol in castrated rats.

Effect of in vitro treatment of rat hepatocytes with selenium, and/or cadmium on cell viability, glucose output, and cellular glutathione

The effects of cadmium as cadmium acetate and selenium as sodium selenite on glucose output, cell viability, and glutathione levels in rat hepatocytes were evaluated. Isolated hepatocytes (200 mg wet wt cells) derived from naive male Sprague--Dawley rats (210-260 g) were incubated at 37 degrees C, with sodium acetate (C2H3NaO2; NaAc) 12.5 microM, 6.3 microM, 3.2 microM; cadmium acetate (C4H6CdO4; Cd) 12.5 microM, 6.3 microM, 3.2 microM; sodium selenite (Na2SeO3; Se) 25 microM, 12.5 microM, 6.3 microM; or Se (6.3 microM) and Cd (3.2 microM). After an incubation period of 2 h, glucose output, cell viability, and reduced glutathione (GSH) levels were determined. The results obtained indicate that incubation of hepatocytes with Se (12.5 or 25 microM) or Cd (3.2, 6.3, or 12.5 microM) resulted in a significant decrease in glucose output, cell viability, and glutathione levels (P less than 0.05) when compared to those incubated with NaAc (control). Selenium in concentrations of 6.3 microM decreased glutathione levels and cell viability only. The damaging effects induced by Cd on hepatocytes were significantly greater than those induced by Se. The decrease in glutathione levels observed following Cd treatment was considerably lowered when Se was concurrently added to the incubation medium. These findings suggest that Se may in part protect against the deleterious effects of Cd on hepatocytes.

Effects of zinc on spatial reference memory and brain dopamine (D1) receptor binding kinetics in rats.

1. The present study was designed to evaluate the effects of zinc on spatial reference memory and brain dopamine (D1) receptor binding kinetics in rats. Male Sprague-Dawley rats (120-150 g), adapted 12 hour light: 12 hour dark illumination cycle were used. Treated animals were given zinc chloride (25 mg/kg, 50 mg/kg, or 100 mg/kg) by oral gavage for 15 days at 11:00 hr. Controlrats received an equivalent volume of saline. 2. Spatial reference memory was evaluated in treated and control rats on days 10 through 15 using the Morris Water Maze. The time to find the platform (latency) was significantly increased in the 50 mg/kg and 100-mg/kg zinc treated animals as compared to the controls. One hour after the last spatial reference memory testing, the animals were sacrificed by decapitation; their brains were removed and dissected into various regions. 3. D1 receptor binding kinetics were measured using the ligand [3H] SCH23390. Results obtained indicate that zinc chloride administration resulted in a statistically significant decline in the binding affinity (increased Kd) of the D1 receptors in the frontal cortex, hypothalamus, hippocampus, and midbrain. However, there was a significant increase in the D1 receptor binding capacity (Bmax) in these same brain regions following zinc chloride administration. 4. These findings clearly indicate that administration of high doses of zinc to rats resulted in spatial reference memory deficit, which may in part be explained by alterations in dopamine receptor binding kinetics.

Alteration of D1 and D2 Dopaminergic Receptor Kinetics in Specific Rat Brain Regions following Repeated Administration of Opiates

The present study was conducted to investigate the effects of repeated administration of opiates on the binding characteristics of D1 and D2 dopamine receptors in specific rat brain regions. Male Sprague-Dawley rats (150-175 g) were adapted for 1 week under controlled conditions (22 +/- 1 degree C, 40% relative humidity, 12 h light:12 h dark illumination cycle). After the adaptation period, rats were randomly assigned into six groups (n = 15/group) for two sets of experiments; one for D1 and the other for D2 receptor binding evaluation. In each set, group 1 served as saline control, group 2 was treated with morphine (1 mg/kg/day for 7 days) and group 3 was treated with naloxone (2 mg/kg/day for 7 days). Following the third day of morphine injection, rats showed restlessness, hyperactivity, increased urination, diarrhea, lacrimation, irritability and squealing on touch, head and body shakes and salivation just prior to morphine dosage. These observed signs are typical for morphine withdrawal. One hour after the last injection, rats were sacrificed by decapitation, brains were removed and kept at -70 degrees C. The frozen brains were further dissected into cortex (CTX), hypothalamus (HYPO), hippocampus (HIPP) and midbrain (MID), pooled (5/pool), homogenized and used for radioreceptor assays. For D1 binding study, 3H-SCH-23390 was used as ligand and for D2 receptor binding 3H-YM-09151-2 was employed. Following repeated morphine or naloxone treatment, Bmax values for 3H-SCH-23390 binding to membranes of HYPO and MID were increased and decreased, respectively, whereas Kd values were significantly decreased in both HYPO and MID of morphine and naloxone-treated animals. In rat brain CTX, both morphine and naloxone decreased Kd and Bmax values of 3H-SCH-23390 binding, however the decrease in Bmax values noted after morphine administration was not statistically significant. Decrease in both Bmax and Kd values of dopamine D1 receptors were observed after naloxone but not morphine treatment in HIPP. Morphine administration increased the density of D2 receptors in HIPP and MID and decreased the affinity of 3H-YM-09151-2 binding in CTX, HIPP and MID. Naloxone treatment resulted in increased number of 3H-YM-09151-2 binding sites in CTX, HYPO and HIPP. While naloxone treatment increased Kd values of 3H-YM-09151-2 in HYPO and HIPP, it decreased these values in CTX and MID. It is concluded that repeated intermittent treatment with opiates induces alterations in D1 and D2 dopamine receptors binding properties and that these changes are regionally specific.(ABSTRACT TRUNCATED AT 400 WORDS)

Selenium and cadmium induced pulmonary functional impairment and cytotoxicity

Ovalbumin-sensitized (50 mg/kg, i.p.) male Hartley-guinea-pigs (550-610 g; n = 6) were treated 14 days later intratracheally with saline, cadmium (Cd 0.3 mg), selenium (Se 0.3 mg or 0.06 mg) or Se (0.06 mg) with Cd (0.3 mg). After 24 h, baseline dynamic-lung-compliance (Cdynl) and pulmonary-resistance (Rp), and percent change after ovalbumin-aerosol-challenge (10 mg/ml, 60 s) were assessed. Cadmium or Se (0.3 mg), Se (0.06 mg) and/or Cd (0.3 mg) decreased Cdynl (P < 0.05). Selenium (0.3 mg) increased Rp (P < 0.05). Ovalbumin-challenge decreased Cdynl and increased Rp in all groups. Analysis of bronchoalveolar-lavage-fluid (BALF) displayed increased activities of lactate-dehydrogenase (LDH), beta-glucuronidase (beta-G), alkaline-phosphatase (AP), and protein due to 0.3 mg Se, 0.3 mg Cd alone or with 0.06 mg Se (P < 0.05). Findings indicated that, 0.3 mg Se is more detrimental than 0.3 mg Cd to lung-dynamics despite a modest protection by 0.06 mg Se against Cd illustrated by an ameliorated Cdynl and lower protein in BALF.

ESTRADIOL AND PROGESTERONE ALTER ETHANOL-INDUCED EFFECTS ON μ-OPIOID RECEPTORS IN SPECIFIC BRAIN REGIONS OF OVARIECTOMIZED RATS

This study was conducted to evaluate the effects of estradiol and progesterone on ethanol-induced alterations of mu-opioid receptor binding kinetics in specific brain regions. Female ovariectomized rats were injected with ethanol (3 g/kg, i.p.), estradiol (50 microg/kg, s.c.) and/or progesterone (5 mg/kg, s.c.), or ethanol plus estradiol and/or progesterone daily for 7 days. Control animals received saline and olive oil. Brains were immediately removed and the cortex, hippocampus, hypothalamus, and midbrain were dissected and assayed for mu-opioid receptor binding kinetics. In the hypothalamus, ethanol alone and in combination with estradiol and/or progesterone significantly decreased Bmax. Ethanol alone also decreased Bmax in the midbrain and cortex. When administered with estradiol only, ethanol increased Bmax and Kd in the hippocampus. The administration of estradiol alone and progesterone alone decreased Bmax in the hypothalamus, while not affecting Bmax in any of the other brain regions. However, when estradiol and progesterone were combined, Bmax, as well as Kd, increased in the cortex. Progesterone alone and in combination with estradiol also increased Kd in the midbrain. In addition, Kd significantly increased following administration of ethanol in combination with either of the hormones, or both, in the midbrain and cortex. These results clearly indicate that the female hormones modulate the effects of ethanol on binding kinetics of mu-opioid receptors in specific brain regions. The present findings may in part explain sex differences in alcohol effects.