The effect of single and chronic administration of imipramine on clonidine-induced hypothermia in the rat

The effect of imipramine (IMI) on the hypothermic action of clonidine, 50 μg/kg iv., was examined after a single dose and after 7, 14 and 21 days of IMI administration in doses of 2 and 10 mg/kg i.p. in rats. Single administration of IMI both in a dose of 2 and 10 mg/kg does not effect clonidine-induced hypothermia. IMI in a dose of 10 mg/kg given for one week significantly blocks the response to clonidine administration, but it has practically no effect in a dose of 2 mg/kg. After a three-week treatment also a dose of 2 mg/kg blocks clonidine-induced hypothermia. It has been demonstrated that the chronic administration of IMI in contrast to the single one significantly blocks clonidine hypothermia.     

The effect of a peat-based preparation on mitogen-induced proliferation of thymocytes in non-treated and hydrocortisone-suppressed mice.

The studies were carried out on Balb/c mice (5-6 weeks of age) treated with a peat-based preparation (PBP), administered i.p. once or four times at 24 h intervals at doses of 0.01; 0.1 or 1 mg/kg. Additionally, hydrocortisone was injected i.p. to selected mice at a single dose of 125 mg/kg. The results show that PBP temporarily enhances the proliferative capability of murine thymocytes stimulated in vitro with concanavalin A (Con A) and phytohemagglutinin (PHA). The effect of PBP depends on the number of subsequent doses, but does not depend on the dose applied. A single PBP administration does not affect the proliferative response of thymocytes to Con A and PHA. A single injection of PBP (doses from 0.01 to 1 mg/kg) does not change the number of thymic cells and weight ratio of this organ. Increased doses of subsequent PBP injections (0.01 and 0.1 mg/kg) do not affect the number of thymocytes, but temporarily increase the weight ratio of the thymus two days after the last injection. Administration of PBP prior to hydrocortisone prevents the suppressive effect of the drug on proliferative response of thymocytes stimulated in vitro with Con A and PHA, at the same time increasing the proliferative response of thymic cells to the two mitogens in relation to the control group (hydrocortisone-free). The effect of a single dose of PBP depends on the dose applied--the weakest preventive effect was observed at a dose of 0.01 mg/kg. An increase in the number of subsequent PBP doses, irrespective of a dose applied, prolongs the protective action of the drug on proliferative activity of thymocytes stimulated in vitro with these mitogenes. Moreover, the results obtained in the studies show that PBP partially prevents the suppressive effect of hydrocortisone, as the number of thymic cells and weight ratio of this organ drastically decreased. PBP accelerates regeneration of the thymus, but this depends on a dose applied and the number of subsequent doses. The result was the strongest and the fastest when PBP was injected four times at a dose of 1 mg/kg. It seems quite likely that the thymic regeneration due to PBP is connected with the effect of this drug on maturation and differentiation of thymic cells.     

Synthesis of DNA in the liver and testes of cadmium-tested partially hepatectomized rats.

Cadmium affects the induction of thymidine and thymidylate kinases in regenerating rat liver. EDTA administered simultaneously with cadmium reverses its inhibitory action on enzyme synthesis, and prevents the depression of thymidine incorporation into DNA observed in cadmium-treated animals. Zinc does not abolish the inhibitory action of cadmium on the synthesis of DNA in regenerating liver, and the incorporation of thymidine into DNA in the testes was inhibited more by intraperitoneal injection of cadmium plus zinc than by injection of cadmium alone. Inhibition of thymidine incorporation into DNA in the liver and testes was proportional to the amount of cadmium administered up to about 2 mg CdCl2/kg body weight, but surprisingly, higher doses of cadmium caused less inhibition.     

Structure of the mesenteric lymph nodes in fetuses and offspring of white rats under the effect of indomethacin on the mother-fetus system

Mesenteric lymph nodes in fetuses and offspring of white rats have been studied during various age periods after indomethacin injection in doses 2.5 mg/kg and 1 mg/kg daily from the 18th up to 21st day of pregnancy. Dose-dependent retardation in formation of main structures of the mesenteric lymph nodes, decreasing amount of the lymphoid type cells have been revealed. Retardation in the capsule, sinuses and reticular fibers of the node takes place, as well as decrease in lympho- and plasmocytopoiesis. It is more pronounced after indomethacin in dose 2.5 mg/kg. Simultaneously, formation of the cerebral substance and appearance of lymphoid nodules and their germinative centers are delayed. After the drug effect (2.5 mg/kg), up to the age of 2 weeks the amount of tissue basophils and eosinophilic granulocytes decreases. When the dose of the drug is 1 mg/kg decreasing amount of these cells is substituted for their compensatory increase on the 2d-3d week. The data obtained demonstrate a decreasing function of the lymph nodes, that depends on the dose of indomethacin.     

Effects of L-arginine on prevention and treatment of lithium-pilocarpine-induced status epilepticus

The effects of various doses of L-arginine, a nitric oxide substrate, on lithium-pilocarpine-induced seizures were studied in rats. Rats were implanted with chronic, stainless steel screw electrodes epidurally for electrocortical recordings. A control group received 3 mEq/kg LiCl (i.p.) and 24 h later 45 mg/kg pilocarpine HCl (i.p.). Two different experimental procedures were followed: (1) L-arginine was applied in doses of 100 mg/kg, 300 mg/kg or 500 mg/kg (i.p.), 30 min before pilocarpine injection; (2) 300 mg/kg, 500 mg/kg or 1000 mg/kg (i.p.) L-arginine was injected either 5 min or 30 min after the onset of status epilepticus (SE). L-arginine (300 mg/kg) injected 30 min before pilocarpine significantly reduced the percentage of SE, but did not change the latency to SE or 24-hour survival. These parameters were not significantly affected by the 100 mg/kg or 500 mg/kg dose of L-arginine. On the other hand, no dose of L-arginine that was applied after SE had begun, had any significant influence on the seizures. We concluded that L-arginine may prevent seizure activity in some but not all doses, and does not have any effect on the ongoing seizure activity.     

Effect of clomiphene citrate on the ovary of a wild rat, Bandicota bengalensis

The effects of clomiphene citrate (0.3 or 3.0 mg/kg body weight/day) for 10 consecutive days on the ovary of a wild rat, Bandicota bengalensis, were studied. The low dose of clomiphene decreased the number of nonatretic follicles larger than 400 microns in diameter, increased atresia in follicles smaller than 200 microns, inhibited granulosal mitosis in follicles less than 200 microns and between 401 and 600 microns in diameter and inhibited thecal mitosis in follicles smaller than 400 microns and larger than 600 microns. The high dose of clomiphene increased the number of follicles between 201 and 400 microns, decreased the number of follicles larger than 600 microns, increased atresia in follicles of 51-400 microns and increased granulosal mitosis in follicles of 201-400 microns diameter. In both the doses, clomiphene inhibited the ovulation rate (p less than 0.005), with 25 and 35% of the rats being anovulatory in low and high doses, respectively. In addition, clomiphene caused irregularity in the estrous cycles associated with increased cycle length. These results suggest that the clomiphene-induced partial inhibition of ovulation is possibly through its action on follicular growth and atresia mainly in nonantral (less than 200 microns) and mature follicles (401-600 microns).     

Effect of chronic D-fenfluramine administration on rat hypothalamic serotonin levels and release

D-fenfluramine, an anorectic agent in rats and man, was administered daily at doses 1.25, 2.5, 5 or 10 mg/kg/day for 10 days, and sacrificed 6 days later. Hypothalamic serotonin (5-HT) levels were unchanged in rats receiving 1.25-5 mg/kg/day of d-fenfluramine but reduced by 22% (p less than 0.01) at the highest drug dose (10 mg/kg/day); hypothalamic 5-hydroxyindole acetic acid (5-HIAA) levels were reduced by 15% (p less than 0.05) or 28% (p less than 0.01) in rats receiving 5 or 10 mg/kg/day of the drug, respectively. Hypothalamic slices prepared from rats which were previously treated with any of the drug doses spontaneously released endogenous 5-HT at rates that did not differ from those of vehicle-treated rats. 5-HT released with electrical field-stimulation was unaffected by prior d-fenfluramine treatment at doses of 1.25-5 mg/kg/day, and was reduced by 20% (p less than 0.05) from slices prepared from rats which received 10 mg/kg/day. 5-HIAA efflux was also attenuated by the highest drug dose. These data indicate that chronic administration to rats of customary anorectic doses of d-fenfluramine (i.e. 0.06-1.25 mg/kg) fail to cause long-lasting reductions in brain 5-HT release.     

Naloxone antagonism of diazepam-induced feeding in the Syrian hamster

Three experiments investigated the effects of the intragastric administration of the benzodiazepine diazepam on feeding in non-deprived Syrian hamsters ($\text{mesocricetus auratus}$). In the first experiment diazepam (0, 0.5, 1.0, 2.0, and 4.0 mg/kg) produced dose dependant increases in feeding. 4.0 mg/kg of diazepam produced significantly more feeding than the other doses tested and the lowest dose tested (0.5 mg/kg) produced a significant increase in feeding. In the second experiment naloxone (10 mg/kg) partially antagonized the effect of 4 mg/kg of diazepam on feeding. In the third experiment the ability of naloxone (0.1, 1.0, 5.0, 10.0 or 20 mg/kg) to reduce feeding produced by either 4 mg/kg or 2 mg/kg of diazepam was tested. Naloxone partially antagonized the effects of 4 mg/kg of diazepam on feeding in a dose dependant manner. While 2 mg/kg of diazepam produced significantly less feeding than 4 mg/kg, naloxone did not antagonize the effect of 2 mg/kg on feeding. The results suggest that two mechanisms are involved in diazepam-induced feeding in hamsters. The high dose of diazepam may produce increased feeding by activating the endorphin system while the low dose of diazepam produces increased feeding via a naloxone insensitive mechanism.     

Biphasic effects of yohimbine on the ejaculatory response in the dog

The effects of various doses (0.01-1.00 mg/kg) of yohimbine, an alpha-2 adrenoceptor antagonist, on the erectile and ejaculatory response elicited by manual penile stimulation were investigated in male dogs. Systemic administration of yohimbine caused a biphasic effect on ejaculatory response; the amount of ejaculate produced by the genital stimulation (for 5 min) was dose-dependently increased by low doses (0.01-0.10 mg/kg) of yohimbine, whereas it was decreased by the highest dose (1.00 mg/kg) of yohimbine. The erectile potency was attenuated only, by the highest dose of yohimbine. The most effective dose (0.10 mg/kg) of yohimbine on ejaculation did not affect the duration of penile erection after removing the genital stimulation. In a stereoisomer's testing, the stimulatory effect on ejaculation was also observed by rauwolscine, an alpha-2 adrenoceptor antagonist (0.03 and 0.10 mg/kg), but not by corynanthine, an alpha-1 adrenoceptor antagonist (0.10 and 0.30 mg/kg). These results suggest that yohimbine at low doses specifically facilitate the ejaculatory response through the blockade of the alpha-2 adrenoceptors. This study also indicates that the effects of yohimbine on male genital responses vary with its dosage used.     

Enkephalin-like immunofluorescence in nerves of the rat iris following systemic capsaicin injection

A network of nerve fibers with an enkephalin-like immunoreactivity was demonstrated in rat iris whole mounts. Systemic administration of capsaicin in doses which caused partial (5 mg/kg) or complete (50 mg/kg) disappearance of substance P-containing fibers in the iris did not cause degeneration of enkephalin-positive nerve fibers. The enkephalin-immunoreactive network seemed intact also after a capsaicin dose of 250 mg/kg. In fact, the fluorescence intensity of the nerve fibers showing enkephalin-immunoreactivity was often increased three days after a capsaicin injection in a dose of 50 mg/kg. The mechanism behind this effect of capsaicin remains to be elucidated, but could be due either to a direct effect on the enkephalin-positive nerves or involve the disappearance of substance P nerves and/or a simultaneous inflammatory response. However, an increased fluorescence intensity of the enkephalin-immunoreactive fibers was sometimes seen also without capsaicin treatment.     

Influence of substance P on the behavioral changes induced by haloperidol in rats

Locomotor activity and grooming behavior of rats were recorded for a period of 30 min following intraventricular injections of substance P(SP) in doses of 0.60 and 2.50 microgram/rat. The lower dose of the peptide significantly increased locomotion for 10 min and time spent grooming for 25 min. The effects of the same two doses of SP on the hypokinesia induced by various pharmacological treatments modifying catecholaminergic systems were then examined. SP did not affect the behavioral depression produced by alpha-methyl-para-tyrosine (250 mg/kg), FLA-63 (25 mg/kg) and phenoxybenzamine (20 mg/kg). However, SP, in dose of 0.60 microgram/rat, systematically reversed the decrease in locomotor activity induced by a relatively small dose of haloperidol, 0.1 mg/kg. The dame dose of the peptide significantly counteracted the rigidity but not the hypokinesia and catalepsy resulting from the previous administration of a higher dose of haloperidol, 3 mg/kg. The results support the hypothesis that SP may exert direct or indirect function in motor behavior, possible via a modulatory action on brain dopaminergic systems.     

The Effect of Atrazine Administered by Gavage or in Diet on the LH Surge and Reproductive Performance in Intact Female Sprague‐Dawley and Long Evans Rats

Atrazine (ATR) blunts the hormone‐induced luteinizing hormone (LH) surge, when administered by gavage (50–100 mg/kg/day for 4 days), in ovariectomized rats. In this study, we determined if comparable doses delivered either by gavage (bolus dose) or distributed in diet would reduce the LH surge and subsequently affect fertility in the intact female rat. ATR was administered daily to intact female Sprague‐Dawley (SD) or Long Evans (LE) rats by gavage (0, 0.75 1.5, 3, 6, 10, 12, 50, or 100 mg/kg/day) or diet (0, 30, 100, 160, 500, 660, or 1460 ppm) during one complete 4‐day estrous cycle, starting on day of estrus. Estrous status, corpora lutea, ova, and LH plasma concentrations were evaluated. A second cohort of animals was mated on the fourth treatment day. Fertility metrics were assessed on gestational day 20. A higher portion of LE rats had asynchronous estrous cycles when compared to SD rats both during pretreatment and in response to ATR (≥50 mg/kg). In contrast, bolus doses of ATR (≥50 mg/kg) inhibited the peak and area under the curve for the preovulatory LH surge in SD but not LE animals. Likewise, only bolus‐treated SD, not LE, rats displayed reduced mean number of corpora lutea and ova. There were no effects of ATR administered by gavage on mating, gravid number, or fetus number. Dietary administration had no effect on any reproductive parameter measured. These findings indicate that short duration, high‐bolus doses of ATR can inhibit the LH surge and reduce the number of follicles ovulated; however, dietary administration has no effect on any endocrine or reproductive outcomes     

Reproductive toxicologic evaluations of Bulbine natalensis Baker stem extract in albino rats

The effects of oral administration of aqueous extract of Bulbine natalensis Baker stem at daily doses of 25, 50, and 100 mg/kg body weight on the reproductive function of Wistar rats were evaluated. The indices of mating and fertility success as well as quantal frequency increased after 7 days of treatment in all the dose groups except the 100 mg/kg body weight group. The number of litters was not statistically different (P > 0.05) from the control. Whereas the absolute weights of the epididymis, seminal vesicle, and prostate were not affected, that of the testes was significantly increased. The epididymal sperm count, motility, morphology, and viscosity were not different from the control after 7 days of treatment. The male rat serum testosterone, progesterone, luteinizing hormone, and follicle-stimulating hormone significantly increased in the 25 and 50 mg/kg body weight groups, whereas the estradiol concentration decreased significantly at all the doses. The extract dose of 100 mg/kg body weight decreased the serum testosterone and progesterone levels in male rats. The prolactin concentration was not affected by all the doses. All the indices of reproduction, maternal, embryo/fetotoxic, teratogenic, and reproductive hormones in the female rats were not statistically different from that of their control except the resorption index, which increased at the dose of 100 mg/kg body weight of the extract. Histologic examination of the cross section of rat testes that received the extract at all the doses investigated revealed well-preserved seminiferous tubules with normal amount of stroma, normal population of spermatogenic and supporting cells, as well as normal spermatocytes within the lumen. The results revealed that the aqueous extract of Bulbine natalensis stem at doses of 25 and 50 mg/kg body weight enhanced the success rate of mating and fertility due to increased libido as well as the levels of reproductive hormones in male rats. The absence of alterations in the reproductive parameters of female rats at doses of 25 and 50 mg/kg body weight of Bulbine natalensis stem extract suggest that the extract is “safe” for use at these doses by females during the organogenic period of pregnancy, whereas the extract dose of 100 mg/kg body weight portends a negative effect on some reproductive functions of male and female rats.     

Analgesic efficacy of orally administered buprenorphine in rats

The analgesic effect of orally administered buprenorphine was compared with that induced by a standard therapeutic injected dose (0.05 mg/kg of body weight, s.c.) in male Long-Evans rats. Analgesia was assessed by measuring pain threshold, using the hot-water tail-flick assay before and after administration of buprenorphine. The results suggest that a commonly used formula for oral buprenorphine in flavored gelatin, at a dose of 0.5 mg/kg, does not increase pain threshold in rats. Instead, oral buprenorphine doses of 5 and 10 mg/kg were necessary to induce significant increases in pain threshold. However, these doses had to be administered by orogastric infusion because the rats would not voluntarily eat flavored gelatin containing this much buprenorphine. The depth of analgesia induced by these infused doses was comparable to that induced by the clinically effective s.c. treatment (0.05 mg/kg).     

Induction of experimental diabetes in frog (author's transl)]

The effect of diabetogenic agents, alloxan and streptozotocin, in frogs has been studied. These drugs were administered to the animals by injection into the dorsal lymph sac. Alloxan did not exert any effect at non-lethal doses. At 300 mg/kg alloxan caused death of most of the animals in an hyperglycemic state in less than 72 hours. Streptozotocin at doses lower than 1 g/kg was ineffective. At 1.5 g/kg, a non-lethal dose, about half of the animals became diabetic.     

Oestrogenic sensitivity of rat uterine secretion.

Ovariectomized adult rats with closed uteri were treated for 7 days with different oral and s..c. doses of oestradiol, oestrone, oestriol and ethinyl oestradiol. All treatments elicited the production of uterine fluid and the potencies of oestrogens were related to the amount of fluid secreted. Ethinyl oestradiol and oestradiol displayed similar activity when given s.c. A daily dose of 0-003 mg oestradiol/kg resulted in about 700 mg fluid. Oestrone was 3-10 times and oestriol about 100 times less active. Orally, ethinyl oestradiol was the most potent substance and 700 mg secretion was obtained with a dose of 0-03 mg/kg daily. Oestradiol was about 30 times, oestrone about 100 times and oestriol 50 times less active than ethinyl oestradiol by this route. The viscosity of the secretion was unaffected, remaining between 1-6 and 2-4 cP. The pH of the fluid did not change, but that of the uterine lumen diminished slightly. These effects of oestrogens were associated with an increase in the weight of the empty uterus and a decrease in body weight.     

Hepatic storage and biliary excretion of rose bengal in the rat

The distribution of intravenously administered rose bengal (RB) depends on its dose. At a low dose (10 mg/kg), RB can be found almost solely in the liver and plasma. However, at higher doses (from 25 up to 200 mg/kg) the amount of RB found in extra-hepatic tissues gradually increases. In this experiment the hepatic transfer maximum of RB amounted to 146 micrograms/kg/min. By increasing the dose from 10 to 200 mg/kg, the hepatic concentration of RB also approached a maximum (1250 micrograms/g). The storage capacity of the liver, however, did not limit the transfer maximum of RB.     

Mutagenicity of the human bladder carcinogen 4-aminobiphenyl to the bladder of Muta ™Mouse transgenic mice

The human carcinogen 4-aminobiphenyl (4AB) was evaluated in the Muta ™Mouse transgenic mouse mutation assay. A single oral dose of 75 mg/kg induced 6.9-, 1.8- and 2.2-fold increases in the mutation frequency (MF) in the bladder, liver and bone marrow, respectively. Ten daily oral doses of 10 mg/kg 4AB increased the MF in the bladder, liver and bone marrow by 13.7-, 4.8- 2.4-fold the control value, respectively. The repeat dosing protocol was therefore more sensitive than the single dose protocol. Assessment of DNA samples prepared from pooled liver homogenates clearly indicated the increase in MF observed in the individual liver samples obtained from both groups of 4AB-treated mice.     

Influence of enkephalinase inhibitors on gastric emptying in mice depends on the nature of the meal

The effects of two enkephalinase inhibitors (thiorphan and acétorphan) and DALAMIDE on gastric emptying of fat or non-fat meals were evaluated in mice. When administered intraperitonally at low doses (0.1 and 0.2 mg/kg) 30 min prior to a fatty (milk) meal, both thiorphan and acetorphan increased significantly (P less than 0.01) gastric emptying; these effects were maximal for 0.2 and 0.1 mg/kg respectively and decreased progressively to be not significant for doses higher than 5 mg/kg for thiorphan and 0.5 mg/kg for acetorphan. Similarly DALAMIDE given IP increased significantly (P less than 0.05) gastric emptying at doses of 0.5 and 1 mg/kg while a slowing of gastric emptying was obtained for 10 times higher doses. The effects of thiorphan (0.2 mg/kg) and DALAMIDE (0.5 mg/kg) were blocked by previous administration of naloxone (0.3 mg/kg) and methyl-naloxone (0.5 mg/kg) while only naloxone (0.3 mg/kg) blocked the slowing effect of high dose of DALAMIDE. Administered prior to a non-fat meal, thiorphan (1 mg/kg) stimulated gastric emptying and inhibited it at higher dosage (10 mg/kg). Neither acetorphan nor DALAMIDE at similar dosages affected the gastric emptying of a non-fat meal and the effects of thiorphan (1 and 0.1 mg/kg) were not blocked by naloxone (0.3 mg/kg). It is concluded that enkephalinase inhibitors (thiorphan and acetorphan) administered systemically stimulate the gastric emptying of a fat meal by increasing enkephalin levels in peripheral tissues, while thiorphan exhibits non-opiate effects on gastric emptying of a non-fat meal.     

Comparison of the ulcerogenicity of indomethacin and the gastric secretion in verapamil-treated rats

The authors studied the effect of different doses of verapamil on the ulcerogenic activity of indomethacin (20 mg.kg-1) in rats. This was compared with the effect of verapamil on total gastric juice secretion, the amount of acid and the pH. It was found that, as distinct from total secretion and the amount of HCl, which verapamil reduced in correlation to the dose, ulcerogenicity after indomethacin was inhibited the most by a dose of 10 mg.kg-1 verapamil. Larger doses (20 and 30 mg.kg-1) did not increase the anti-ulcerogenic effect any further. This implies that verapamil-induced inhibition of the ulcerogenicity of indomethacin is not related directly to inhibition of total and acid gastric juice secretion.