Metoclopramide potentiates the hypophyseal reactions to oestradiol

Male rats to which oestradiol benzoate was administered intramuscularly twice a week for three weeks in 1 mg doses as an aqueous microcrystal suspension showed an increase in adenohypophyseal weight, in the number of lactotropic cells in the adenohypophysis (demonstrated by immunohistochemical detection of prolactin) and in polyphenol oxidase (ceruloplasmin) activity in the blood and hypothalamus. The simultaneous administration of metoclopramide (methoxychloroprocainamide) in doses of 10 mg/rat per day in food potentiated the adenohypophyseal reaction to oestradiol (weight and the number of lactotropic cells), but potentiated the polyphenol oxidase reaction only little or not at all. Metoclopramide thus has an anti-dopaminergic effect similar to that of perphenazine and other inhibitors of dopaminergic neurones.     

Dopaminergic antagonists potentiate the adenohypophyseal growth reaction to oestrogen: thioridazine is less effective than perphenazine

The injection of oestradiol benzoate as an aqueous microcrystal suspension, in a dose of 1 mg twice a week, evokes a marked adenohypophyseal growth reaction in male rats. The reaction is potentiated by dopaminergic antagonists from the group of neuroleptics (specifically perphenazine and thioridazine). Elicitation of the same adenohypophyseal reaction required twice as much thioridazine (10 mg/rat per day) as perphenazine. Thyroxine inhibited the adenohypophyseal growth reaction to oestradiol. The serum polyphenol oxidase (ceruloplasmin) level rose after oestradiol and perphenazine and thioridazine slightly potentiated the increase.     

The effect of hexose monophosphate shunt inhibitors on adenohypophyseal and ceruloplasmin reactions to oestrogen.

Oestradiol benzoate, as an aqueous microcrystal suspension, was administered i.m. to rats in doses of 1 mg twice a week; it induced adenohypophyseal hyperplasia and an increase of the thyroxine-binding capacity of the adenohypophyseal proteins in vitro and raised the blood ceruloplasmin level. The simultaneous administration of a hexose monophosphate shunt inhibitor--6-aminonicotinamide (200 microgram/rat/day in food) or oxythiamine (8 mg/rat/day in food)--did not modify the reaction of the adenohypophysis; the hexose monophosphate shunt thus probably does not play a significant role in the adenohypophyseal reaction to oestrogens. By themselves, both inhibitors raised the blood ceruloplasmin level and their effect summated with that of oestradiol. The mechanism of action of the inhibitors is not known, but a nonspecific stress effect leading to an increase in the ceruloplasmin level as an "acute phase protein" is considered to be the most likely.     

Reactions of hypothalamic ascorbic acid, serum ceruloplasmin and the adenohypophysis to oestradiol: inhibition by L-thyroxine

Four weeks' administration of oestradiol benzoate to male and female rats in doses of 1 mg twice a week leads to adenohypophyseal hyperplasia and to an increase in the thyroxine-binding capacity of the adenohypophyseal proteins in vitro. At the same time, serum polyphenol oxidase (ceruloplasmin) activity rises and the hypothalamic ascorbic acid concentration falls. The simultaneous administration of L-thyroxine (0.1 mg/rat/per day) or dried thyroid (but not D-thyroxine) significantly inhibits these changes (adenohypophysis, ceruloplasmin) or completely suppresses them (hypothalamic ascorbic acid). L-thyroxine evidently blocks the action of oestradiol in the adenohypophysis, the liver and the hypothalamus; the significance of this inhibition is discussed in relation to dopaminergic modulation of the adenohypophyseal reaction to oestradiol.     

Interaction of perphenazine and an ergoline derivative on oestrogen-induced adenohypophyseal growth.

Male and female rats were injected twice a week for three weeks with doses of 1 mg oestradiol benzoate (OE), were given perphenazine (P, 2 mg/rat/day) or the ergoline derivative D-6-methyl-8-ergoline-(I)-yl acetic acid amide (Deprenon SPOFA, D, 200 microng/rat/day) in their food or were treated with various combinations of all three factors. OE-induced adenohypophyseal growth was inhibited by D, but the inhibitory effect of D was completely suppressed by P. D also inhibited the OE-induced increase in the thyroxine-binding capacity of the adenohypophyseal proteins, but this inhibition was not suppressed by the simultaneous administration of P. The administration of OE was followed by elevation of the serum ceruloplasmin level, which was not inhibited by P or D, either alone or combined. Ovarian weight rose markedly after D and the increase was inhibited by the simultaneous administration of either OE or P.     

Modulation of the effect of oestradiol on adenohypophyseal weight: ineffectiveness of nickel chloride, potentiation by cimetidine

Male rats received an i.m. injection of oestradiol benzonate twice a weak, as an aqueous microcrystal suspension in doses of 1 mg, and/or were given, in their food, nickel chloride in daily doses of 10 mg [first experiment] or 20 mg [second experiment] per rat, or cimetidine, an antagonist of H2 receptors, in daily doses of 20 mg [first experiment] or 40 mg [second experiment] per rat. Neither dose of nickel chloride affected the oestrogen-induced growth reaction of the adenohypophysis, the increase in polyphenol oxidase [ceruloplasmin] activity in the blood [the larger dose stimulated it slightly], the increase in hypothalamic polyphenol oxidase activity or the post-oestrogen drop in the hypothalamic ascorbic acid concentration. Both doses of cimetidine potentiated the growth reaction of the adenohypophysis to oestrogens, but did not affect the blood polyphenol oxidase, the hypothalamic polyphenol oxidase or the hypothalamic ascorbic acid reaction. If administered alone, the larger dose of cimetidine mildly reduced serum polyphenol oxidase [ceruloplasmin] activity.     

Inhibition of thyroxine binding to adenohypophysial proteins in vitro by 2,4-dinitrophenol administered in vivo.

Male and female rats were given oestradiol benzoate (1 mg as a microcrystal aqueous suspension i.m. twice a week), 0.0033% 2.4-dinitrophenol (DNP) in their food (about 1 mg/rat/day), or 0.1% DNP in their food (about 30 mg/rat/day), or both oestradiol and DNP. The smaller DNP dose mildly stimulated food consumption and did not affect body weight. The larger dose strongly inhibited food consumption in the first two weeks of the experiment; consumption then returned to the control level, but body weight fell markedly at the same time. After 3 weeks' administration of both the small and the large dose of DNP, adrenal weight in the males was raised and the weight of the gonads was unchanged. The large DNP dose severely reduced the weight of the seminal vesicles and the uteri. It also inhibited the accumulation of radioiodine in the thyroid of both males and females. Isolated administration of the oestrogen raised adrenal weight in the males and ovarian and uterine weight in the females; it reduced the weight of the testes and seminal vesicles. These reactions were not affected by DNP. A pronounced oestradiol-induced increase in the weight of the adenohypophyses was accompanied by raised thyroxine binding to the adenohypophysial proteins in vitro. DNP inhibited the growth reaction of the adenohypophysis to the oestrogen only slightly and non-significantly, but significantly inhibited the thyroxine binding reaction to the adenohypophysial proteins in vitro. By itself, DNP had no effect on adenohypophysial weight, but reduced thyroxine binding to the adenohypophysial proteins in vitro, especially in males. The effect of DNP was similar to that of thyroxine observed in earlier experiments; nothing is known of its mechanism.     

Effect of interaction of oestrogen, testosterone and thyroid hormones on the serum ceruloplasmin level in rats.

Male rats were given oestradiol benzoate (1 mg as an aquaeous microcrystal suspension i.m. twice a week), testosterone isobutyrate (0.5 mg as an aquaeous microcrystal suspension i.m. once a week) and dried thyroid (Thyreoidin SPOFA, 0.2% in food), alone or variously combined. Oestradiol raised adenohypophyseal weight, the binding capacity of the adenohypophyseal proteins for thyroxine and the serum ceruloplasmin level. Testosterone and Thyreoidin inhibited all three of these reactions, but when they were administered together there was no summation of their inhibitory action. The nature of the relationships between the three given proteosynthetic reactions is discussed.     

Dopaminergic control of adenohypophyseal growth after oestrogens: negative results with L-DOPA, RO-4-4602, alpha-methyl-DOPA, apomorphine, haloperidol, pyridoxine and cyproheptadine.

Chronic oestrogen treatment augments adenohypophyseal weight and the thyroxine-binding capacity of adenohypophyseal proteins in rats. Since these reactions are both inhibited by ergocornine and ergoline derivatives (as well as by the thyroid hormones, testosterone, anti-oestrogens and antiandrogens), and are potentiation by perphenazine and the dopaminergic neurone blocker Pimozide, the peroral effectiveness of various other substances presumed to act in the region of the dopaminergic or serotoninergic neurones of the hypothalamus was tested. L-DOPA (10 mg/rat/day) did not modify the adenohypophyseal reaction, either alone or combined with the DOPA-decarboxylate inhibitor Ro-4-4602 (1 mg/rat/day). alpha-Methyl-DOPA (10 mg/rat/day), apomorphine (3 mg/rat/day), haloperidol (0.2 mg/rat/day), pyridoxine (20 mg/rat/day) and cyproheptadine (1 mg/rat/day) were likewise ineffective.     

Effect of oestrogen and ascorbic acid on the serum ceruloplasmin level in rats.

The administration of long-acting oestrogen (1 mg twice a week for 3 weeks) is followed, in rats, by an increase in the serum ceruloplasmin concentration to about 150% of the control value. The simultaneous administration of ascorbic acid in a dose of 10, 20 or 50 mg/rat/day in food raises the ceruloplasmin concentration to 180-200% of the control value (no significant difference was observed in the effect of the various doses of ascorbic acid). The increase produced by combining ascorbic acid with the oestrogen amounts to 20-30% of the value recorded in animals treated only with oestrogen. The mechanism by which ascorbic acid potentiates the effect of oestrogens on the ceruloplasmin level is not known.     

Inhibition by an ergoline derivative (dopaminergic agonist) of oestradiol-induced adenohypophyseal growth and of the decrease in the hypothalamic ascorbic acid (HAA) concentration in rats

The increase in adenohypophyseal weight and the decrease in the ascorbic acid concentration in the hypothalamus of rats injected i.m. twice a week with oestradiol benzoate as an aqueous microcrystal suspension in doses of 2.65 mumol (1 mg) was completely (HAA) or almost completely (adenohypophyseal weight) inhibited by the simultaneous administration of the ergoline derivative D-6-methyl-8-ergoline-(1)-yl acetic acid amide (Deprenon SPOFA) in the diet in daily doses of 0.28 mumol (200 micrograms) per rat. The functional significance of HAA in dopaminergic modulation of oestrogen-induced adenohypophyseal growth is discussed, with special reference to the possible function of HAA as a dopamine-beta-hydroxylase cofactor.     

Increased number of beta-adrenergic receptors on cells of the rat adenohypophysis after thyroid hormone administration

The authors studied the effect of administration of thyroid hormones on the beta-adrenergic receptors of rat adenohypophyseal cells. The administration of triiodothyronine and thyroxine was followed by an increase in specific binding for 3H-dihydroalprenolol. No significant differences were found in cyclic adenosine monophosphate levels before and after isoprenaline stimulation. The significance of changes in these receptors for the hyperplastic reaction after oestrogens is discussed with reference to the inhibitory effect of the thyroid hormones on hyperplasia of the adenohypophyseal cells after the administration of oestradiol.     

GABAA receptors in nucleus accumbens shell mediate the hyperphagia and weight gain following haloperidol treatment in rats

AimsWeight gain is a common outcome of antipsychotics therapy in schizophrenic patients. However, the underlying neuronal mechanisms are unclear. The present study was undertaken to investigate the role of GABA_A receptors within the framework of nucleus accumbens shell (AcbSh) in haloperidol-induced hyperphagia and body weight gain in sated rats.Main methodsIn acute studies, GABA_A receptor agonists muscimol, diazepam or antagonist bicuculline were administered by AcbSh route, alone or in combination with haloperidol (intraperitoneal/ip). Immediately after these treatments, preweighed food was offered to the animals at commencement of dark phase. Cumulative food intake was measured at 2 and 6 h post-injection time-points. Furthermore, effects of subacute haloperidol treatment, alone or in combination with muscimol, diazepam or bicuculline, on food intake and body weight were investigated.Key findingsWhile acute treatment with haloperidol, muscimol or diazepam dose dependently stimulated the food intake, bicuculline suppressed the same. Prior administration of muscimol (20 ng/rat, intra-AcbSh) and diazepam (5 µg/rat, intra-AcbSh) significantly potentiated, whereas bicuculline (40 ng/rat, intra-AcbSh) negated the hyperphagic effect of acute haloperidol (0.005 or 0.01 mg/kg/rat, ip). Subacute administration of haloperidol (0.01 mg/kg/rat/day, ip) for 15 days produced increase in food intake and body weight. Although, concomitant administration of muscimol (20 ng/rat/day, intra-AcbSh) or diazepam (5 μg/rat/day, intra-AcbSh) markedly enhanced, bicuculline (40 ng/rat/day, intra-AcbSh) prevented the subacute haloperidol-induced hyperphagia and weight gain.SignificanceThe results of present study suggest that increased food intake and body weight following haloperidol treatment in rats, may be mediated via AcbSh GABA_A receptors.     

Strain differences in the dose-response curves of adrenalectomized, starved-refed rats to dehydroepiandrosterone (DHEA)

The effects of adrenalectomy and dehydroepiandrosterone (DHEA) doses (0, 15, 30, 60, 120 and 240 mg/kg/day ip) on hepatic enzyme activity and lipid content and on the amount of epididymal fat pad lipid were studied in starved-refed BHE and Sprague-Dawley rats. BHE rats had significantly greater relative liver size, glucose-6-phosphate dehydrogenase (G6PD) and malic enzyme (ME) activities, and percentage liver lipid but less epididymal fat pad lipid than Sprague-Dawley rats. Adrenalectomized (ADX) rats consumed significantly less food, gained less weight per day, and had less lipid in their livers and fat pads than intact rats. As the level of DHEA increased from 0 to 240 mg/kg/day there was a significant linear decrease in average daily weight gain, food intake, G6PD activity, and percentage liver lipid. At the 15 mg/kg/day dose, G6PD activity was significantly reduced without reductions in the other parameters measured. At the 120 mg/kg/day dose, however, weight gain, food intake, G6PD activity, and percentage liver lipid were significantly lower than that of the controls. At this dose DHEA treatment reduced food intake by 17% whereas it diminished average daily weight gain and G6PD activity by 30 and 56%, respectively. The 240 mg/kg/day dose of DHEA significantly reduced food intake, weight gain, liver lipid, G6PD activity, and ME activity. Intact and ADX BHE rats reduced their G6PD activity and liver lipid more rapidly than Sprague-Dawley rats as the level of DHEA administered increased. ADX Sprague-Dawley rats receiving DHEA had greater liver lipid content and enzyme activity than their intact counterparts whereas the reverse situation was true in BHE rats. These data indicate that the effect of DHEA on body weight gain, food intake, and hepatic and peripheral adiposity are dependent on the strain of rat, the adrenal status, and the DHEA dose.     

Effect of continuous infusions of dexfenfluramine on food intake, body weight and brain amines in rats

The present experiments describe the effects of continuous SC infusion, via osmotic minipump, of dexfenfluramine on food intake and body weight of male and female rats. It was found that the food intake of male rats was reduced by infusions of both 3 and 6 mg/kg/day although tolerance developed within 2-4 days at the lower dose. Further, these rats showed tolerance to an acute anorectic test dose of dexfenfluramine. Body weight loss was sustained by both groups. In older (6-8 mo old) female rats, some of which had previously nursed three litters, the anorectic effects of dexfenfluramine (3 and 6 mg/kg/day) were sustained throughout the 6 day infusion, and weight loss was substantial. The effects did not differ between bred and virgin rats of comparable age. The lower dose of dexfenfluramine produced no depletion of brain serotonin (5HT), although 5HIAA was reduced. Both compounds were depleted by the higher dose. The 3 mg/kg/day dose, in select rat populations, may be a close model for the mode of dexfenfluramine administration to humans.     

Estradiol-induced adenohypophyseal growth reaction and beta-adrenergic receptors.

The effect of administration of estradiol benzoate on beta-adrenergic receptors of rat adenohypophyseal cells was studied. Twenty days' administration of estradiol benzoate was followed by an increase of adenohypophyseal weight and a decrease in specific binding of 3H-dihydroalprenolol (3H-DHA). In contrast to thyroid hormone treatment which induced an increase in 3H-DHA binding, thyroid hormone treatment decreased both the growth reaction and the reaction of beta-adrenergic receptors after estradiol. Although the relationship between the adenohypophyseal receptors and the growth reaction is unclear, changes in beta-adrenergic receptors after hormonal therapy can be one of pathophysiological conditions that may influence this reaction.     

The activating effect of ceruloplasmin on the development of delayed hypersensitivity in mice

The influence of ceruloplasmin on the development of delayed hypersensitivity (DHS) and activity of T-suppressors were studied in experiments on intact Balb/c mice. Ceruloplasmin introduced in a dose of 5 mg per 1 kg of weight a day before immunization of animals is shown to have a stimulating effect. The amount of the introduced drug being raised to 200 mg per 1 kg of weight suppressed the ability of organism to form DHS effect rather than increased it. Ceruloplasmin is stated to inhibit induction of DHS suppressors and to exert no effect on the expression of functional activity of the formed suppressors.     

Effect of colchicine and demecolcine on the serum ceruloplasmin level in rats.

Six hours after the administration of demecolcine (0.3 mg/100 g b.w.), a decrease in the ceruloplasmin level was recorded in rat serum. The time course of the decrease in the rat serum ceruloplasmin concentration after the same dose of colchicine was then studied. After two to three hours, the serum ceruloplasmin concentration fell significantly in both male and female rats. Eight hours after the administration of colchicine, the serum ceruloplasmin level began to rise again in female rats, but not in male rats. Mortality among females was lower than among males.     

Dose–Response Effects of Diphenylhydantoin on Pregnant Dams and Embryo‐Fetal Development in Rats

Despite the widespread use of diphenylhydantoin (DPH), there is a lack of reliable information on the teratogenic effects, correlation with maternal and developmental toxicity, and dose–response relationship of DPH. This study investigated the dose–response effects of DPH on pregnant dams and embryo‐fetal development as well as the relationship between maternal and developmental toxicity. DPHwas orally administered to pregnant rats from gestational days 6 through 15 at 0, 50, 150, and 300 mg/kg/day. At 300 mg/kg, maternal toxicity including increased clinical signs, suppressed body weight, decreased food intake, and increased weights of adrenal glands, liver, kidneys, and brain were observed in dams. Developmental toxicity, including a decrease in fetal and placental weights, increased incidence of morphological alterations, and a delay in fetal ossification delay also occurred. At 150 mg/kg, maternal toxicity manifested as an increased incidence of clinical signs, reduced body weight gain and food intake, and increased weights of adrenal glands and brain. Only minimal developmental toxicity, including decreased placental weight and an increased incidence of visceral and skeletal variations, was observed. No treatment‐related maternal or developmental effects were observed at 50 mg/kg. These results show that DPH is minimally embryotoxic at a minimal maternotoxic dose (150 mg/kg/day) but is embryotoxic and teratogenic at an overt maternotoxic dose (300 mg/kg/day). Under these experimental conditions, the no‐observed‐adverse‐effect level of DPH for pregnant dams and embryo‐fetal development is considered to be 50 mg/kg/day. These data indicate that DPH is not a selective developmental toxicant in the rat.     

Changes induced in adrenergic lipolysis by the administration of diethylstilboestrol, oestradiol and clomiphene

The authors studied changes in adrenergic lipolysis in the epididymal adipose tissue of rats to which diethylstilboestrol and oestradiol combined with the anti-oestrogen clomiphene were administered. The maximum lipid-mobilizing effect of isoprenaline was increased not only by subcutaneously administered diethylstilboestrol, but also by the highest dose of the antioestrogen clomiphene used (p.o., 200 micrograms.kg-1 b.w.). Under the given experimental conditions, with 4 1/2 h incubation of adipose tissue, clomiphene was also effective when added in vitro. Its own oestrogenic effect probably stimulated the lipid-mobilizing action of isoprenaline. On combining the administration of increasing doses of clomiphene (p.o., 1-5 days) with a constant dose of oestradiol (200 micrograms.kg-1, s.c. on the 8th day, i.e. 24 h before the actual experiment), changes in isoprenaline lipolysis depended on the dose of clomiphene. In low doses clomiphene inhibited the stimulating effect of subsequently administered oestradiol on isoprenaline-induced lipolysis, but in large doses (100 and 200 micrograms.kg-1 daily) it potentiated, together with oestradiol, the lipid-mobilizing effect of isoprenaline. The results show that the non-steroid oestrogen diethylstilboestrol and the antioestrogen clomiphene may be included among the hormones capable of altering the response of adipose tissue to sympathomimetics (isoprenaline). We attribute the fact that clomiphene acted either as an antagonist or as an agonist of oestradiol to its combined oestrogenic and anti-oestrogenic effects.