Quipazine-metoclopramide inhibition of CB-154-induced prolactin suppression in rats: neurotransmitter-metabolite correlations

Subacute toxicity of alpha-ergocryptine in Sprague-Dawley rats. 1: general toxicological effects

The dietary subacute toxicity of the ergot alkaloid alpha-ergocryptine was studied in Sprague-Dawley rats. Rats were fed 0, 4, 20, 100 or 500 mg ergocryptine/kg diet for 28-32 days (equal to 0, 0.36, 1.7, 8.9 and 60 mg ergocryptine/kg body weight/day for females and 0, 0.34, 1.4, 6.6 and 44 mg ergocryptine/kg body weight/day for males). The present study describes the general toxicological effects; the effects on metabolic and hormonal parameters will be reported separately. Body weight, body weight gain, food intake and food efficiency were all decreased with a U-shaped dose-response curve, as in both sexes the ranking severity of effects was in the order 100-20-500 and 4 mg/kg diet. Other changes with a U-shaped dose-response relationship included: hematological parameters (decreased MCV and MCH), serum enzyme activities (slightly increased/decreased ALAT, ASAT, GGT), increased serum urea concentrations, decreased glomular filtration (creatinine and urea clearances), decreased absolute organ weights, increased and decreased relative organ weights, atrophy of thymus and in females atrophy of ovary and uterus with in the mid-dose groups no detectable morphological features of an oestric cycle in the uterus. Other parameters, including increased relative liver, heart and ovarian weights and necrosis of the tail, were influenced in a dose-related manner or only in the high dose group. The U-shaped changes for the parameters mentioned above might be caused by the U-shaped dose-response relationship for food intake, which may be explained by the dopaminergic properties of alpha-ergocryptine. It is concluded that in rats fed ergocryptine for 28 days the dose-effect curve is rather steep and that the NOAEL is 4 mg/kg diet.

Subacute toxicity of alpha-ergocryptine in Sprague-Dawley rats. 2: metabolic and hormonal changes

The present study describes the metabolic changes observed in a dietary subacute toxicity experiment with the ergot alkaloid alpha-ergocryptine in Sprague-Dawley rats. The observed effects on metabolic and hormonal parameters were described separately from the general toxicological effects, in view of the important role of dopamine agonists in metabolism (e.g. ergot alkaloids in fescue toxicosis). The rats were fed 0, 4, 20, 100 or 500 mg ergocryptine/kg diet for 28-32 days (equal to 0, 0.36, 1.7, 8.9 and 60 mg ergocryptine/kg body weight/day for females and 0, 0.34, 1.4, 6.6 and 44 mg ergocryptine/kg body weight/day for males). Total cholesterol and high-density lipoprotein (HDL)-cholesterol were decreased dose dependently in females but the ratio HDL-cholesterol/total cholesterol was only decreased at 20 mg/kg body weight. Triglycerides and glucose concentrations were decreased in the highest dose groups of both sexes. Serum urea concentrations were increased in the 20, 100 and 500 mg/kg dose groups. Insulin, glucagon and liver glycogen were increased in the highest dose group at the end of the study, when the animals were allowed to eat prior to blood sampling and necropsy. Prolactin, T4 and FT4 were decreased in the 20, 100 and 500 mg/kg dose groups of both sexes. Follicle-stimulating hormone (FSH) was decreased in the 20, 100 and 500 mg/kg female dose groups and luteinizing hormone (LH) was increased in the 20, 100 and 500 mg/kg male dose groups. It is postulated that the observed effects on food intake, metabolism (lipid and carbohydrate) and hormonal parameters are due to an interaction of ergocryptine with central dopaminergic activities, which comprise a major functional component of a central regulatory system for metabolism.

Effects of metoclopramide and quipazine on serum prolactin concentrations in steers

The dopamine antagonist metoclopramide monohydrochloride (MC) and the serotonin agonist quipazine maleate (Q) were administered to steers by both the oral and intravenous (i.v.) routes. Dose-response studies were designed to determine the effects of these drugs on serum prolactin (PRL) concentrations. Parameters subjected to analysis included maximal serum PRL concentrations within 1 h and the areas under the PRL response curves over time. At 1, 4, and 8 mg/kg i.v., and at 15, 30, 45, and 60 mg/kg orally, MC increased (P less than 0.05) serum PRL concentrations (difference between maximal and basal serum PRL concentrations) and increased (P less than 0.05) areas under the PRL response curves except for 1.0 mg/kg i.v. Doses of MC greater than 60 mg/kg and Q at all dosage rates were considered toxic. These studies determined a dose-response to MC in terms of serum PRL concentration and indicate that MC is well tolerated and effective for elevating serum PRL concentrations in steers. Furthermore, 4 mg/kg i.v. and 15 mg/kg orally could be considered the preferred dosage rates due to a plateau in the response above those rates.