Effects of prenatal cocaine exposure on postnatal growth patterns of male Wistar rats

Rats exposed to cocaine during late gestation and early postnatal life show deficits in hippocampal pyramidal and granule cells in later life

In humans, the offspring of maternal cocaine misusers are known to have subtle cognitive and motor impairments in later life. It was therefore hypothesized that such exposure in animals would also affect the morphological structure of the brain. This possibility was investigated by exposing rats to cocaine between embryonic day 15 and postnatal day 6. Samples of the cocaine-exposed and control rats were killed for examination at 22 and 150 postnatal days of age. Stereological procedures (the Cavalieri principle together with the physical disector method) were utilized to estimate the total number of pyramidal and granule cells in defined regions of the hippocampal formation. At 22 days of age, the control offspring had about 373 000 pyramidal cells whereas the cocaine-treated animals only had about 310,000 cells in the CA1 + CA2 + CA3 region. By 150 days of age the values were about 396,000 and 348,000, respectively. The differences between age-matched groups were statistically significant. There were about 626,000 and 687,000 dentate gyrus granule cells in the 22-day-old control and cocaine-treated groups, respectively. By postnatal day 150 the control rats had about 832,000 granule cells whilst the cocaine-treated rats had about 693,000. There was a significant main effect of age as well as group-age interaction in this measure. These results show that even moderate exposure to cocaine during the late gestation and early postnatal period in rats is a potent teratogen and can markedly influence the development of neurons in the hippocampal formation.

Myelination changes in the rat optic nerve after prenatal exposure to methamphetamine

The use of psychostimulants during adolescence and early adult life has increased in recent years. It is known that these substances affect the sensory systems, and the optic nerve has been shown to be a target tissue. This work was conducted to evaluate the effects of prenatal exposure to methamphetamine (MA) on the developmental pattern of the rat optic nerve. Pregnant female rats were given 5 mg/kg body weight/day MA, s.c., in 0.9% saline from gestational days 8 to 22. The control group was injected with an isovolumetric dose of 0.9% saline. Animal model parameters, such as gestational body weight evolution, food intake and pups parameters were registered. The offspring were sacrificed at postnatal days (PND) 7, 14 and 21. Morphometric analyses were performed at light and electron microscopic levels on optic nerve cross sections; parameters measured included optic nerve diameter and area, axonal density, total number of axons and myelin thickness. Myelin basic protein (MBP) was measured by western blotting in optic nerve samples at PND14 and PND21. The animal model parameters, such as maternal and pup weight, showed no significant differences between MA and control groups. Optic nerve diameter was smaller at PND7 in the male MA group and in both male and female MA groups at PND21. The mean cross-sectional area was smaller at PND14 in the male MA group and in both male and female groups at PND21. The total number of myelinated axons did not vary between groups at any of the studied ages. The myelin thickness of the axons in MA-treated females was thinner when compared with the respective control group at PND21. No other differences were found concerning myelin thickness. There was a reduction of MBP protein expression in MA-injected females at PND14 and PND21. The combined results suggest that prenatal exposure to MA affects the myelination process.

Prenatal cocaine exposure accelerates morphological changes and transient expression of tyrosine hydroxylase in the cochlea of developing rats

Prenatal cocaine exposure causes alterations in auditory brainstem response in children and experimental animals and has adverse effects on auditory information processing and language skills in children. These effects may result from lesions in the cochlea since this organ is particularly sensitive to chemical insults during the development. We have thus studied here the effect of prenatal cocaine exposure on the maturation of the rat cochlea using the transient non-catecholaminergic expression of tyrosine hydroxylase in spiral ganglion neurons as an index of cochlear maturation and morphometry to evaluate the maturation of primary auditory neurons and the organ of Corti. We showed that prenatal cocaine exposure accelerated the cochlear maturation. In the basal coil of cochleas from PND8 cocaine-treated pups, the Kölliker's organ had disappeared, the tunnel of Corti was opened, and the stria vascularis no longer contained undifferentiated marginal cells. The maximum expression of tyrosine hydroxylase in type I primary auditory neurons occurred at PND8 instead of PND12 in pair-fed controls. On the other hand, the prenatal cocaine exposure had no effect on the width and height of the organ of Corti, spiral ganglion volume and number and size of primary auditory neurons. In conclusion, our data suggest that prenatal cocaine exposure, though not lethal to primary auditory neurons, accelerates aspects of the cochlear sensorineural maturation. This accelerated cochlear maturation in cocaine-treated rat pups could cause auditory dysfunctions by desynchronizing the development of the whole auditory pathway.

Detection of 2,4-dichlorophenoxyacetic acid in rat milk of dams exposed during lactation and milk analysis of their major components

2,4-Dichlorophenoxyacetic acid (2,4-D) and its derivatives are herbicides widely used to control the growth of broadleaf and woody plant. Human and animal exposure to 2,4-D through agriculture use, food products, or use in lawn and garden care has been well documented, but little information is available on the transfer from serum to milk in exposed dams. In this study, we measured the content of 2,4-D in rat milk from mother exposed to 15, 25, 50 or 7 0mg 2,4-D/kg bw through the diet (4 treated groups, 8 dam each; 1 control group with 8 dams) over a period of 16 days starting on the post-natal day 1 (PND 1). The effect of 2,4-D on milk components was also evaluated. All doses tested caused a decrease in the body weight gain of the pups (4 groups, 64 pups each). It also produce a 30% in the content of total lipids and a changed the content of minor proteins in milk of the treated groups. 2,4-D produces an important decrease in some fatty acids content, being the polyunsaturated fatty acids the most affected. Further analysis showed that 2,4-D concentrations chromatographically detected both serum of dams and pups and milk were dose-dependent.

Methamphetamine and lipid peroxidation in the rat retina

BACKGROUND

The use of psychoactive drugs during adolescence and early adult life has increased in the last few decades. It is known that developmental exposure to psychostimulants affects the sensory systems, and the retina has been shown to be a target tissue. This work was conducted to evaluate the pattern of lipid peroxidation in the rat retina following prenatal exposure to methamphetamine (MA).

METHODS

Pregnant female Wistar rats were given MA (5 mg/kg of body weight/day; SC, in 0.9% saline) from GD 8 to 22. Offspring were sacrificed at postnatal days (PNDs) 7, 14, and 21. The retinas were homogenized, and both the total antioxidant and superoxide dismutase (SOD) activities were measured by enzymatic-colorimetric methods. The lipid peroxidation byproducts (malondialdehyde [MDA] and MDA-like metabolites) were measured by the thiobarbituric acid test.

RESULTS

Total antioxidant levels were lower in the MA group at PND 21 in both males and females. The activity of SOD was higher in PND 7 females from the MA group. MDA levels were higher in the MA group at PND 21 in both genders.

CONCLUSIONS

These findings suggest that prenatal-induced MA toxicity in the retina may be related to lipid peroxidation processes and oxidative stress.

Comparison between two common methods for measuring Giardia lamblia susceptibility to antiparasitic drugs in vitro

In this study a comparison between two different methods for measuring the susceptibility of Giardia lamblia trophozoites to metronidazole and albendazole is performed. Modifications of Meloni's method, based on the loss of adherence of parasites to surfaces, and the Hill method, based on the loss of parasite division capacity, are compared. A logistic model was used to calculate the inhibitory concentrations IC(10), IC(50) and IC(90) that were further compared using the respective standard errors. The results obtained, after contact of parasites with the antiparasitic drugs for 24h, show that the adherence method is more sensitive than the multiplication method for low and moderate inhibitory concentrations of albendazole. Conversely for metronidazole the multiplication method seems to be more sensitive for high inhibitory concentrations of the drug. For screening the IC(50), both methods seem to be effective, however, the inhibition of adherence method have even better performance for the benzimidazole like drugs.

Toxicity of 4-nonylphenol to Tubifex tubifex and Chironomus riparius in 28-day whole-sediment tests

Concern has been growing recently over the toxicity and the mimicking properties of 4-nonylphenol (4NP), the most persistent breakdown product of the nonionic surfactant nonylphenol ethoxylates, broadly used in industrial cleaning processes. Twenty-eight-day tests were performed to evaluate the toxicity and the effects on reproduction of 4NP spiked sediment to the benthic invertebrates Tubifex tubifex and Chironomus riparius. 4NP was directly added to the wet sediment, avoiding any solvent. The EC50 value for the emergence of chironomids was 380 microg 4NP g(-1) dry weight (dw); the EC50 values for the deposition of cocoons and the development of young worms were very similar (428 and 420 microg g(-1) dw, respectively). Regarding NP estrogenic activity and its effects on reproduction and development, no significant differences were noted in the sex ratio of the emerged chironomids when exposed to 4NP compared to the controls, but the emerged chironomids did not lay eggs at concentrations higher than the EC10 (250 microg 4NP g(-1) dw). Furthermore, at concentration of 610 microg 4NP g(-1) dw an interference in the development of the gonads of adult worms was observed, but it was impossible to determine whether this effect was due to 4NP toxicity or to its hormone mimicking properties.

A Daphnia magna first-brood chronic test: An alternative to the conventional 21-Day chronic bioassay?

In this study a comparison was made of the results obtained in Daphnia magna chronic bioassays after first-brood release and after 21 days of exposure, using inhibition of normal reproduction and growth as effect criteria and EC10, EC20, EC50, no-observed-effect concentration (NOEC), and lowest-observed-effect concentration (LOEC) as statistical parameters. Test substances were sodium bromide (NaBr), 3,4-dichloroaniline (DCA), cadmium, and parathion. For NaBr, DCA, and cadmium, toxicity evaluated after the first-brood release was similar to toxicity evaluated after 21 days, using reproduction as end point. Parathion did not affect either reproduction or growth. Thus, LC50, NOEC, and LOEC were calculated using mortality as the endpoint for parathion. Results indicate that the period until release of the first brood is sufficient to predict the toxicity of some chemicals to D. magna. Values estimated on the basis of a logistic model (EC10, EC20, and EC50) were more appropriate than NOECs and LOECs for evaluating toxicity of the test substances. Furthermore, classic endpoints used for the evaluation of chronic toxicity (inhibition of normal reproduction and growth) may not be adequate to evaluate the sublethal toxicity of compounds that induce cumulative effects leading to mortality within the test period and causing no observable effects on the reproduction and growth of the species. Endpoints indicative of biochemical stress or effects on specific targets of the test compound may be useful in sublethal toxicity evaluation.

Differential effects of prenatal exposure to cocaine and amphetamine on growth parameters and morphometry of the prefrontal cortex in the rat

The purpose of this study was to investigate the differential effects of prenatal exposure to psychostimulants, e.g., cocaine or amphetamine, on basic growth parameters and morphometry of the medial prefrontal cortex of the rat. A group of pregnant Wistar rats was given 60 mg/kg body weight/day of cocaine hydrochloride and another group 10 mg/kg body weight/day of d-amphetamine sulfate, subcutaneously, from gestational days 8 to 22. Control groups of pregnant rats were pair-fed; litters were culled to eight pups (4 males and 4 females) weighed every other day until postnatal day 30 and every week until day 90. The body weight growth patterns modelled by a Gompertz curve were different in rats prenatally exposed to the two psychostimulants. Rats exposed to amphetamine had on average a slower growth than those exposed to cocaine, reaching an identical estimated adult weight. Allometric relationships between forebrain and body weight and cerebellum and body weight were described by two distinct postnatal growth phases that are different among the experimental groups. In the comparison of the two psychostimulants the relative cerebellum/body growth is lower in the offspring of the cocaine group than in the amphetamine group between PND14-PND30; between PND30-PND90 the relative growth rate is considerably higher in the offspring of the cocaine dams compared to that of the amphetamine dams. Groups of perfused animals were selected at postnatal days 14 and 30 to analyze the morphometric organization of the medial prefrontal cortex. In serial celloidin sections the volumes of the prefrontal cortex were determined; the number of neurons per unit volume of reference area was calculated using the stereological technique of the disector. The changes found in the morphometric parameters show a catch-up at postnatal day 30 of the "increased" density of neurons of the medial prefrontal cortex found at postnatal day 14. These data show differential growth patterns of offspring from cocaine- and amphetamine-exposed rats; a delayed development in the achievement of normal morphometric parameters of neurons in the prelimbic subarea of the medial prefrontal cortex occurs in the prenatally amphetamine-exposed offspring at early ages, and a catch-up is found after the first month of life. Complementary studies are needed to assess whether these changes have functional implications in the rats exposed prenatally to psychostimulants.

Development of the eye after gestational exposure to cocaine. Vascular disruption in the retina of rats and humans

Clinical and basic research in the area of drugs of abuse are of utmost importance since they provide the necessary background for health programs in one of the main problems of contemporary society. The available data in this field demonstrate that acute, subacute and/or chronic abuse of illicit drugs, e.g., cocaine, alters the neurochemistry and functioning of the neural circuitries. Although recent works demonstrated that the visual system is lesioned after exposure to cocaine during the active periods of development, no studies have provided detailed information on the effects of these substances on the development of this sensory system. The present paper will report: 1) the vulnerability of the developing visual system to gestational exposure to cocaine; 2) the effects of cocaine in the visual system during the more active periods of development in humans and, as far as possible, the establishment of homologies with animal models where exposure is made in corresponding periods of human gestation, and 3) the characterization of the vascular disruption caused by ischemic/hypoxic mechanisms. The clinical study focused the ophthalmologic evaluation of newborns exposed in utero to illicit drugs. Newborns exposed to cocaine in utero showed marked vascular disruption in the retina: superficial and deep hemorrhages that, although morphologically similar to neonatal retinal hemorrhages, presented a longer reabsorption time when compared with the neonatal hemorrhagic lesions due to birth trauma in the general population. Prolonged eyelid edema was also a prominent finding. The animal study was conducted in Wistar rats exposed prenatally (gestational days 8 to 22) and postnatally (postnatal days 1-6, 1-13 and 1-29) to 60 mg/kg body weight/day and 15 mg/kg body weight/day, respectively, to cocaine hydrochloride administered subcutaneously; control groups included pair-feeding during the same experimental periods. Similar alterations to those observed in the newborns where exposure to cocaine was affirmative, were found: intraretinal hemorrhages allied to signs of chronic ischemia both in the outer retina-photoreceptor rosettes and in the inner retina-epiretinal glial membranes. Taking into consideration that the visual system is one of the more important sensory systems, the identification and characterization of these alterations, the similarity between animal and human findings, and their relation with cocaine per se, can provide a sound data base for illicit drug prevention programs.

Effects of prenatal cocaine exposure in the photoreceptor cells of the rat retina

Despite the increasing evidence of eye abnormalities, the effects of prenatal exposure to cocaine on the visual system are still poorly understood. This study was aimed at analyzing the qualitative and quantitative organization of the retinal photoreceptor cells (PR) and outer nuclear layer (ONL) after prenatal exposure to cocaine in the rat. Pregnant Wistar rats were given sc injections of cocaine hydrochloride (60 mg/kg body wt/d) or saline or were not manipulated; analyses were performed in the 14- and 30-d-old male offspring. Radial semithin and ultrathin sections of epon-embedded flat mounts of the retina showed displaced PR-like cells in the inner nuclear layer (INL), picnotic PR nuclei in INL, and ONL, and retinal PR rosettes and outer-segment debris in the subretinal space. The quantitative study showed an increased density of PR-like nuclei in the INL in PND14 cocaine-treated rats that were within normal values at PND30; no changes were detected in the PR mean nuclear diameter and in the packing density of PR nuclei in the ONL. These data constitute the first morphological demonstration of photoreceptor damage after prenatal cocaine-exposure probably owing to a direct action of the drug and/or to the cocaine-induced ischemia/hypoxia.

Effects of prenatal cocaine exposure in the retinal ganglion cell layer of the rat. A morphometric analysis

To study the effects of prenatal cocaine-exposure on the developing retinal ganglion cell layer of the rat, female Wistar rats were administered subcutaneously (sc) cocaine hydrochloride (60 mg/kg body wt/d) or saline, or were not manipulated from gestational d 8-22. Male offspring were sacrificed at postnatal day 14 and 30. Radial semithin sections of epon-embedded flat mounts of the retinal quadrants were used to evaluate the following parameters along the centroperipheral axis: 1. Thickness of ganglion cells plus nerve fiber layer; 2. Nuclear size of ganglion cell layer neurons; and 3. Linear density (number per unit length) of ganglion cell layer neurons. To study the effects of cocaine and age on the retinal areas (temporal/nasal, dorsal/ventral), a repeated measures analysis of variance was used for each of the parameters mentioned above. All parameters were affected by prenatal exposure to cocaine. The thickness of the ganglion cell plus nerve fiber layer was reduced in cocaine-exposed rats in comparison with the saline group. Nuclear diameters were smaller in the cocaine than in the saline and control groups. The linear density was higher in the cocaine-exposed group than in the control and saline groups. The age-dependent decrease in the linear density from postnatal day 14-30 was higher in the cocaine-exposed rats than in the saline group; the decrease in the linear density along the centroperipheral axis found in both the control and saline groups was not significant in the cocaine-treated group. These morphometric findings strongly support the view that prenatal cocaine-exposure induces marked changes in the organization of the developing retina.