Two-generation reproduction study of di-2-ethylhexyl terephthalate in Crl:CD rats

BACKGROUND: This study was conducted to evaluate the potential adverse effects of di-2-ethylhexyl terephthalate (DEHT) on reproductive capability from exposure of F(0) and F(1) parental animals. METHODS: Four groups of male and female Crl:CD (SD)IGS BR rats (30/gender/group) were exposed to 0, 0.3%, 0.6%, and 1.0% DEHT in the feed for at least 70 consecutive days before mating for the F(0) and F(1) generations. Exposure for the F(0) and F(1) males continued throughout the mating period until euthanasia. Exposure for the F(0) and F(1) females continued throughout mating, gestation, and lactation. The F(1) and F(2) pups were weaned on postnatal day (PND) 21. Assessments included gonadal function, estrous cyclicity, mating behavior, conception rate, gestation, parturition, lactation, and weaning in the F(0) and F(1) generations, and F(1) generation offspring growth and development. RESULTS: DEHT exposure did not affect clinical observations. However, lethality was observed in F(0) and F(1) dams consuming the 1.0% diet during the post-weaning period. No treatment-related mortality occurred in any of the male groups exposed to DEHT or in the female groups exposed to 0.3% or 0.6% DEHT. Male rats consuming the 1.0% diet in both parental generations gained weight more slowly than the controls. There were no indications of adverse effects on reproductive performance in either the F(0) or F(1) generation. Male and female mating and fertility indices, pre-coital intervals, spermatogenic endpoints, reproductive organ weights, lengths of estrous cycle and gestation, live litter size, developmental landmarks, and postnatal survival were similar in all exposure groups. Additionally, ovarian follicle counts for the F(1) females in the high-exposure group were similar to the control values. No adverse exposure-related macroscopic pathology was noted at any exposure level in the F(0) and F(1) generations. CONCLUSIONS: Increases in liver weights were found in the male and female animals exposed to 0.6% or 1.0% DEHT in the diet. Because there were no accompanying histopathologic changes, this effect was not considered adverse. Significant decreases in feed consumption in the female animals from the groups consuming 1.0% DEHT in the diet during lactation accompanied reduced postnatal pup body weights and rate of weight gain. Reductions in pup body weights later in lactation may also have been due to direct consumption of the treated feed by the pups or taste aversion to the same. Reduced relative spleen weight was found in male weanling pups from the 1.0% group in both generations and reduced relative spleen and thymus weights were found in female pups from the 1.0% group in the F(2) generation at necropsy on PND 21. Therefore, for parental and pup systemic toxicity, 0.3% DEHT in the diet (182 mg/kg/day) was considered no-observed-effect level (NOEL). The 1.0% DEHT (614 mg/kg/day) in the diet exposure concentration was considered a NOEL for F(0) and F(1) reproductive toxicity endpoints.     

The residual effect of chronic neuroleptic treatment on the neuroleptic binding assay in rats

Chronic chlorpromazine administration to rats (25 mg/Kg/day) for 30 days followed by a washout period of 10 days resulted in an increase in both the measured maximum number of binding sites, Bmax, and the apparent dissociation constant, Kd, for the binding of 3H-spiroperidol to neural membranes of the brain. When membrane suspensions were progressively diluted before the binding assay, it was found that the apparent Bmax did not change with dilution, remaining higher in membranes of chlorpromazine-treated rats than in controls. The apparent increase in Kd, on the other hand, was found to be an artifact of the assay. Thus extrapolation of the measured or apparent Kd value to infinite dilution resulted in identical value for Kd regardless of the treatment.     

Zetidoline, a novel neuroleptic, activates nigral dopaminergic neurons in rats

Zetidoline (ZET), a rather selective dopamine (DA) D2-receptor blocker, was found to be equipotent to haloperidol and over 300 times as potent as sulpiride in activating the firing rate of substantia nigra dopaminergic neurons (SN-DA neurons) in unanesthetized rats. Moreover, like classic and atypical neuroleptics, ZET reversed and prevented apomorphine-induced inhibition of SN-DA neurons.     

Azaperone and azaperone-ketamine as a neuroleptic sedative and anesthetic in rats and mice

Azaperone alone and combined with ketamine were evaluated as sedative and anesthetic agents in outbred rats and mice. Using azaperone alone the duration of immobility was 1.9 to 10.8 hours for mice and 0.9 to 2.4 hours for rats. The withdrawal reflex was not eliminated from mice receiving azaperone alone; however, the withdrawal reflex was eliminated from 0.9 to 2.4 hours in rats receiving azaperone. Azaperone produced a tachypnea in rats and male mice while a depressed respiratory rate was observed in female mice. Using azaperone combined with ketamine, the duration of immobilization was 1.1 to 8.8 hours for mice and 1.3 to 6.0 hours for rats. The duration loss of the withdrawal reflex, which was used as an indication of surgical anesthesia, was 0.9 to 1.8 hours for mice and 1.0 to 6.0 hours for rats. An increase in respiratory rate was observed in rats given the combination while mice given the combination showed transient tachypnea followed by bradypnea. Overall, azaperone alone was shown to provide sedation in mice as compared to a dose dependent anesthesia in rats. The azaperone-ketamine combination produced a surgical plane of anesthesia in both rats and mice. Azaperone and the azaperone-ketamine combination appear to be a suitable alternative to sedatives and anesthetics currently used in rats and mice.     

Differential effects of neuroleptic and other psychotropic agents on acquisition of avoidance in rats.

An avoidance acquisition procedure is presented and discussed, which is specifically sensitive to the effects of clinically effective antipsychotic (neuroleptic) agents and predictive of their clinical potency. The method distinguishes between such compounds and other classes of psychotropic agents. It utilizes experimentally naive rats, thereby obviating the need for maintaining colonies of trained animals, requires no training by the experimenter, and is rapid, requiring only a single, 50 minute test session.     

Prevention of sudden cardiac death by the atypical neuroleptic acepromazine following status epilepticus in rats

Normal male rats in which status epilepticus has been induced by injecting 30 mg/kg of pilocarpine after a single systemic administration of lithium (sufficient to produce blood levels of 0.2 mEq/L) invariably die within 24 hr. Real-time monitoring indicated sudden cardiac death; it was preceded by progressive intensification of arrhythmia. A single systemic injection (25 mg/kg) of the atypical phenothiazine acepromazine prevented the mortality and virtually eliminated the cardiac instability.     

Changes in the number of benzodiazepine receptors in different parts of the brain of rats after neuroleptic withdrawal

It has been demonstrated in experiments on rats receiving chronic (16 days) treatment with haloperidol (1.0 mg/kg/day), sulpiride (50 mg/kg/day) and clozapine (10 mg/kg/day) that binding of 3H-flunitrazepam in the striatum, limbic system, and cortex is reduced at the 5th day after withdrawal of the neuroleptics. That release was determined by the diminution of the number of receptors without changing in the dissociation constant. The reduction in the density of benzodiazepine receptors (BD-receptors) after withdrawal of the neuroleptics attests to their agonistic effect on BD-receptors. Apparently these changes are not linked with a direct effect of the neuroleptics on BD-receptors, since they displace 3H-flunitrazepam in experiments in vitro only at micromolar concentrations. It is assumed that the reduction in 3H-flunitrazepam binding is mediated via the GABAergic system transsynaptically in response to increase in the number of dopamine (neuroleptic) receptors.     

Safety of a novel oxygen-coordinated niacin-bound chromium(III) complex (NBC): I. Two-generation reproduction toxicity study

The objective of this study was to evaluate the effects of a novel oxygen-coordinated niacin-bound chromium(III) complex (NBC) on the reproductive systems of male and female rats, the postnatal maturation and reproductive capacity of their offspring, and possible cumulative effects through multiple generations. Sprague-Dawley rats were maintained on feed containing NBC at dose levels of 0, 4, 15, or 60 ppm for 10 weeks prior to mating, during mating, and, for females through gestation and lactation, across two generations. For the parents (F₀ and F₁) and the offspring (F₁ and F_2a), reproductive parameters such as fertility and mating, gestation, parturition, litters, lactation, sexual maturity and development of offspring were assessed. Results from the current study indicated that dietary exposure of NBC to parental male and female rats of both (F₀ and F₁) the generations during the premating and mating periods, for both sexes, and during gestation and lactation in case of female rats, did not cause any significant incidence of mortality or abnormal clinical signs. Compared to respective controls, NBC exposure did not affect reproductive performance as evaluated by sexual maturity, fertility and mating, gestation, parturition, litter properties, lactation and development of the offspring. Based on the findings of this study, the parental as well as the offspring no-observed-adverse-effect level for NBC was determined to be greater than 60 ppm in diet or equivalent to 7.80 and 8.31 mg/kg body weight/day in male and female rats, respectively.     

During one year's neuroleptic treatment in rats striatal dopamine receptor blockade decreases but serum prolactin levels remain elevated

Rats were treated for one year with either trifluoperazine dihydrochloride (2.5–3.5 mg/kg/day) or thioridazine dihydrochloride (30–40 mg/kg/day) when prolactin levels were measured in comparison to animals treated acutely with a single oral bolus of the same drugs in approximately the same dose. Serum prolactin levels at the end of the year of neuroleptic treatment with either drug remained elevated compared to those in control animals, and the elevation was no different from that obtained by administration of an equivalent acute single oral bolus. In contrast, the inhibition of apomorphine-induced stereotypy produced by the acute administration of either drug disappeared during chronic treatment, to be replaced after a year's neuroleptic administration by a supersensitive response. Similarly, the increase in dopamine turnover produced by acute neuroleptic administration, evidenced by raised striatal 3, 4-dihydroxy-phenylacetic acid (DOPAC) levels, also disappeared at the end of a year's treatment, when specific binding of ³H-spiperone to striatal homogenates indicated an increased number of dopamine receptors. The disappearance of evidence of blockade of striatal dopamine receptors, which appeared to become supersensitive during a year's chronic treatment with either trifluoperazine or thioridazine, contrasts with the persistence of the effect of these drugs on serum prolactin levels.     

Radioimmunoassay of the neuroleptic drug pimozide

Pimozide was made antigenic by coupling it to bovine serum albumin. This pimozide-protein conjugate induced antibodies against pimozide in rabbits. By using the antiserum, the drug could be detected in amounts as low as 50 picogram. The binding capacity of the antibodies was high for pimozide and for the closely related neuroleptic analogues clopimozide, fluspirilene and penfluridol. Therefore, the diphenylbutylamine-moiety of the pimozide molecule was required for strong binding. No cross-reaction was observed with the major metabolites of pomozide, even at 500 times higher concentration, so they will not interfere with a radiommunologic determination of pimozide in human plasma.