2,4-dichlorophenoxyacetic acid through lactation induces astrogliosis in rat brain

2,4-Dichlorophenoxyacetic acid containing herbicide impairs essential visually guided behaviors of larval fish

Aquatic herbicides are used worldwide to eradicate nuisance and invasive plants despite limited knowledge of their toxicity to non-target organisms. 2,4-Dichlorophenoxyacetic acid (2,4-D) is a common active ingredient in commercial herbicide formulations, which triggers plant cell death by mimicking the plant-specific hormone auxin. Application practices of 2,4-D commercial herbicides typically coincide with yearly freshwater fish spawning periods. This practice exposes fish to xenobiotics at their vulnerable larval stages. The full impacts of 2,4-D on larval fish remains poorly understood, and hence, whether it may alter larval survival, larval behavior, fish populations, and ecosystem dynamics. In the present study, we exposed embryonic and larval zebrafish (Danio rerio) to the active ingredient 2,4-D (pure 2,4-D) or a 2,4-D containing commercial herbicide DMA4^®IVM (DMA4) and evaluated morphology, survival, behavior, and nervous system function. At 2,4-D concentrations producing no overt morphological defects during embryonic or early larval stages, we observed reduced survival throughout a 21-day larval assay (4-8 ppm DMA4 and 0.75-4 ppm pure 2,4-D). Notably, prey capture, a behavior essential to survival, was reduced in 2,4-D-exposed larval zebrafish (4-8 ppm DMA4 and 0.75-4 ppm pure 2,4-D) and yellow perch (Perca flavescens) (4-20 ppm DMA4). In zebrafish, 8 ppm DMA4 exposure reduced prey capture when exposure was restricted to the period of visual system development. Consistent with these results, larval zebrafish exposed to 8 ppm DMA4 showed reduced neural activity within the optic tectum following prey exposure. Together, our results suggest that 2,4-D alters the development and function of neural circuits underlying vision of larval fish, and thereby reduces visually guided behaviors required for survival.

The Calcineurin Inhibitor FK506 Prevents Cognitive Impairment by Inhibiting Reactive Astrogliosis in Pilocarpine-Induced Status Epilepticus Rats

Status epilepticus (SE) is a severe clinical manifestation of epilepsy accompanying with cognitive impairment and brain damage. Astrocyte activation occurs following seizures and plays an important role in epilepsy-induced pathological injury, including cognitive impairment. FK506, an immunosuppressant used in clinical settings to prevent allograft rejection, has been shown to exhibit neuroprotective effects in central nervous system diseases. The present study was designed to investigate the effect of FK506 on cognitive impairment in a lithium-pilocarpine-induced SE rat model. It's found that FK506 treatment significantly increased the latency period to seizures and decreased the maximal intensity of seizures. FK506 treatment also markedly increased the surviving cells and reduced the neuron apoptosis after seizures. Meanwhile, FK506 treatment reduced the escape latency and prolonged the swimming distance in the Morris water maze test. In addition, FK506 treatment down-regulated the expression level of GFAP, a specific marker of astrocytes. In conclusion, FK506 could prevent and recover cognitive impairment by inhibiting reactive astrogliosis in pilocarpine-induced status epilepticus rats, suggesting that FK506 may be a promising agent for the treatment of epilepsy.

Epi/perineural and Schwann Cells as Well as Perineural Sheath Integrity are Affected Following 2,4-D Exposure

2,4-dicholorophenoxy acetic acid (2,4-D) is a worldwide-known hormone herbicide. However, there are increasing concerns about its exposure and risks of developing pathological conditions for the peripheral nervous system. The aim of this study was to investigate the mechanism(s) involved in the toxicity of 2,4-D on peripheral nerve's cellular components. The epi/perineural and Schwann cells and a total of three cell lines were treated with 2,4-D. The viability of cells at different doses of 2,4-D was measured by MTT assay. The cell cycle analyses, cumulative cell counting, fluorescent staining, antioxidant and caspase enzymes activity were examined on epi/perineural and Schwann cells. The epi/perineural cells were assessed as having biological macromolecular changes. Some tight junction-related genes and proteins were also tested on explants of 2,4-D treated epi/perineural tissue. The viability of 2,4-D treated cells was reduced in a dose-dependent manner. Reduced growth rate and G1 cell cycle arrest were verified in 2,4-D treated epi/perineural and Schwann cells. The use of staining methods (acridine orange/ethidium bromide and DAPI) and caspase 3/7 activity assay along with malondialdehyde, glutathione peroxidase, and superoxide dismutase activity assays indicated the apoptotic and oxidant effects of 2,4-D on epi/perineural and Schwann cells. Data obtained from FTIR revealed changes in epi/perineural proteins and cell membrane lipids. Additionally, claudin-1, occludin, and ZO-1 gene/protein expression profiles were significantly reduced in 2,4-D-treated epi/perineural pieces. Our data indicated that oxidative stress, apoptosis of epi/perineural and Schwann cell and impaired blood-nerve barrier may have contributed to nerve damage following 2,4-D exposure.

Extra virgin olive oil modulates brain docosahexaenoic acid level and oxidative damage caused by 2,4-Dichlorophenoxyacetic acid in rats

Oxidative stress is an important pathomechanism of neurological disorders such as Alzheimer disease and Parkinson disease, cardiovascular disorders and many others. This study sought to verify whether extra-virgin olive oil (EVOO), lipophilic fraction (OOLF) and hydrophilic fraction (OOHF) exerted a brain protective effect against the oxidative stress caused by 2,4-dichlorophenoxyacetic acid (2,4-D) pesticide at a dose of 5 mg/kg body weight. 2,4-D, EVOO and its fractions were administered to rats by gavages for four consecutive weeks. Oxidative stress was assessed by measuring brain lipid peroxide level, acetylcholinesterase (AChE), antioxidant enzyme activities and fatty acid composition. 2,4-D induced a decrease in both plasma and brain acetylcholinesterase activity and a rise in Brain TBARS (Thiobarbituric acid reactive substances) level and antioxidant enzyme activities compared with the control group. These changes were partly reversed by either EVOO or its fractions oral administration to 2,4-D treated rats. EVOO enhanced a neuroprotective effect evaluated by the restoration of brain fatty acid composition especially the level of docosahexaenoic acid (DHA). Our results indicate that EVOO exerts a neuroprotective activity against oxidative damage in brain induced by 2,4-D, which could be attributed to its antioxidative property.

Increased calcineurin expression after pilocarpine-induced status epilepticus is associated with brain focal edema and astrogliosis

Calcineurin plays an important role in the development of neuronal excitability, modulation of receptor's function and induction of apoptosis in neurons. It has been established in kindling models that status epilepticus induces brain focal edema and astrocyte activation. However, the role of calcineurin in brain focal edema and astrocyte activation in status epilepticus has not been fully understood. In this study, we employed a model of lithium-pilocarpine-induced status epilepticus and detected calcineurin expression in hippocampus by immunoblotting, brain focal edema by non-invasive magnetic resonance imaging (MRI-7T) and astrocyte expression by immunohistochemistry. We found that the brain focal edema was seen at 24 h after status epilepticus, and astrocyte expression was obviously seen at 7 d after status epilepticus. Meanwhile, calcineurin expression was seen at24 h and retained to 7 d after status epilepticus. A FK506, a calcineurin inhibitor, remarkably suppressed the status epilepticus-induced brain focal edema and astrocyte expression. Our data suggested that calcineurin overexpression plays a very important role in brain focal edema and astrocyte expression. Therefore, calcineurin may be a novel candidate for brain focal edema occurring and intracellular trigger of astrogliosis in status epilepticus.

Changes in CNS cells in hyperammonemic portal hypertensive rats

Rats with pre-hepatic portal hypertension because of partial portal vein ligation develop minimal hepatic encephalopathy (MHE) with hyperammonemia, impaired blood-brain barrier, mild brain edema, and severe mitochondrial changes in the hippocampus. The aim of this study was to evaluate changes of different neural cells in the cerebral cortex and the hippocampus. Animals were divided into two groups, MHE and sham. Astrocytes were studied by immunostaining with glial fibrillary acidic protein and S100β protein; neurons were immunostained with neuronal nuclear marker, microtubule associated protein-2, and NF-200 and capillaries with Nestin. The hypoxia-inducible factor 1α (HIF-1α) and its downstream proteins, P-glycoprotein (P-gp) and erythropoietin receptor (Epo-R), were also evaluated. Astrocytes were increased in area and number only in the hippocampus, while S100β increased in both brain areas in MHE animals. Microtubule associated protein-2 and NF-200 immunoreactivities (-ir) were significantly reduced in both areas. Hippocampal Nestin-ir was increased in MHE animals. These cellular changes were similar to those described in ischemic conditions, thus HIF-1α, P-gp, and Epo-R were also evaluated. A high expression of HIF-1α in cortical neurons was observed in the MHE group. It is likely that this hypoxia-like state is triggered via ammonia occupying the binding domain of HIF-1α and thereby preventing its degradation and inducing its stabilization, leading to the over-expression of P-gp and the Epo-R.

2,4-Dichlorophenoxyacetic acid effects on nephrotoxicity in rats during late pregnancy and early postnatal periods

2,4-Dichlorophenoxyacetic acid (2,4-D) is largely used as a selective herbicide in Tunisia. The purpose of this study was to investigate the effects of 2,4-D on the kidneys of adult rats and their suckling pups. Female Wistar rats were divided into two groups: the controls and the treated rats that received 600 mg/L of 2,4-D in their drinking water from the 14th day of pregnancy until day 14 after delivery. Exposure to 2,4-D induced nephrotoxicity as evidenced by an increase in thiobarbituric acid reactive substances and protein carbonyl levels and a decrease in antioxidant enzyme activities such as catalase, superoxide dismutase, glutathione peroxidase in the kidneys of suckling pups and their mothers. In addition, a significant decline in kidney glutathione, non-protein thiol and vitamin C levels was also observed. Histological changes, seen in the kidney of mothers and their pups treated with 2,4-D are characterized by a narrowed Bowman's space, tubular epithelial cells degeneration, widened tubular lumen and vascular congestion.

Selective Oxidative Stress in Brain Areas of Neonate Rats Exposed to 2,4-Dichlorophenoxyacetic Acid Through Mother's Milk

2,4-Dichlorophenoxyacetic acid (2,4-D) induced disparate alterations on enzymatic activities of the defensive mechanism and/or modifications of the reactive oxygen species levels in specific neonate rat brain regions. The midbrain, striatum, and prefrontal cortex were the areas where the alterations were more remarkable and with similar tendency. The hippocampus did not suffer many alterations, and the hypothalamus was the area where no changes were observed. The current results suggest that the developing brain areas have different susceptibilities to the adverse effect of the herbicide, especially those areas related to the dopaminergic system, and that oxidative stress is one 2,4-D mechanism of toxicity.

Melatonin decreases the oxidative stress produced by 2,4-dichlorophenoxyacetic acid in rat cerebellar granule cells

2,4-Dichlorophenoxyacetic acid (2,4-D) is one of the most widely used herbicides due to its relatively moderate toxicity and to its biodegradability in the soil. In toxic concentrations, 2,4-D displays strong neurotoxicity, partly due to generation of free radicals. Since melatonin has remarkable antioxidant properties, the objective of this study was to assess to what extent it was effective in preventing the 2,4-D effect on redox balance of rat cerebellar granule cells (CGC) in vitro. Cellular viability, generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS), reduced glutathione (GSH) levels, and the activities of the antioxidant enzymes Cu/Zn-superoxide dismutase (Cu/Zn-SOD), Mn-SOD, selenium-glutathione peroxidase (Se-GPx) and catalase (CAT) were measured in CGC exposed to 2,4-D and/or melatonin for 48 h. In CGC cultures exposed to 2,4-D, cell viability, GSH levels and CAT activity decreased significantly whereas ROS generation and Se-GPx activities were augmented. Except for Se-GPx activity, all these changes were counteracted by the concomitant addition of 0.1 or 0.5 mM melatonin. In addition, incubation of CGC with melatonin alone resulted in augmentation of cell viability, GSH levels and Se-GPx activity. RNS generation and SOD activity remained unaffected by either treatment. Since melatonin was able to counteract most of redox changes produced by 2,4-D in CGC in culture, the experimental evidence reported further support the efficacy of melatonin to act as a neuroprotector.

A low chronic ethanol exposure induces morphological changes in the adolescent rat brain that are not fully recovered even after a long abstinence: An immunohistochemical study

Little is known about the morphological effects of alcoholism on the developing adolescent brain and its consequences into adulthood. We studied here the relationship between two neurotransmitter systems (the serotoninergic and nitrergic) and the astrocytic and neuronal cytoskeleton immediately and long after drinking cessation of a chronic, but low, ethanol administration. Adolescent male Wistar rats were exposed to ethanol 6.6% (v/v) in drinking water for 6 weeks and studied after ending exposure or after a 10-week recovery period drinking water. Control animals received water. Brain sections were processed by immunohistochemistry using antibodies to serotonin (5-HT); glial fibrillary acidic protein (GFAP); astroglial S-100b protein; microtubule associated protein-2 (MAP-2); 200 kDa neurofilaments (Nf-200); and neuronal nitric oxide synthase (nNOS). The mesencephalic dorsal and median raphe nucleus (DRN; MRN) and three prosencephalic areas closely related to cognitive abilities (CA1 hippocampal area, striatum and frontal cortex) were studied by digital image analysis. 5-HT immunoreactivity (-ir) decreased in the DRN and recovered after abstinence and was not changed in the MRN. In the three prosencephalic areas, astrocytes' cell area (GFAP-ir cells) increased after EtOH exposure and tended to return to normality after abstinence, while cytoplasmic astroglial S100b protein-ir, relative area of MAP-2-ir and Nf-200-ir fibers decreased, and later partially recovered. In the striatum and frontal cortex, nNOS-ir decreased only after abstinence. In conclusion, in the adolescent brain, drinking cessation can partially ameliorate the ethanol-induced morphological changes on neurons and astrocytes but cannot fully return it to the basal state.

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.

Study of tyrosine hydroxylase immunoreactive neurons in neonate rats lactationally exposed to 2,4-dichlorophenoxyacetic Acid

Dopaminergic neurons from the midbrain nuclei substantia nigra (SN; A9) and ventral tegmental area (VTA; A10) were investigated by tyrosine hydroxylase (TH) immunostaining in neonate rat brains exposed to 2,4-dichlorophenoxyacetic acid (2,4-D) through lactation. Dorsal raphe serotonin (5-HT) projections to SN and VTA were also studied by 5-HT transporter (5-HTT) immunostaining and results were quantified by image analysis. Twenty-five-day-old pups exposed to 2,4-D through mothers milk were used. Dams were intraperitoneally administered 70 or 100mg/kg/day of 2,4-D from the 9th to the 25th postpartum day. After 100mg/kg of 2,4-D exposure, a 25% diminution in the SN and a 33% diminution in the VTA neurons' TH immunostaining along with a significantly 5-HT fiber density diminution were observed. The present work supports previous reports which suggest that exposure to 2,4-D during development has multiple effects on CNS.

Effects of 2,4-dichlorophenoxyacetic acid exposure on dopamine D2-like receptors in rat brain

2,4-Dichlorophenoxyacetic acid (2,4-D), a worldwide-used herbicide, has been associated with a range of adverse health effects on humans and different animal species. Although the mechanism of 2,4-D neurotoxicity remains unknown, we had previously reported changes in various neurotransmitter systems, such as serotonin (5-HT) and dopamine (DA), which were proposed to mediate some of the behavioral effects in rats. In the present work, we examined the impact of 2,4-D exposure on the ontogeny of dopaminergic D2-type receptors in prefrontal cortex (PFc), striatum (CPu), hippocampus (H) and cerebellum (Cer). Pregnant rats were orally exposed to 70 mg/kg/day of 2,4-D from gestation day (GD) 16 to postpartum day 23. After weaning, the pups were assigned to one of the two subgroups: T1 [fed with untreated diet until postnatal day, (PD) 90] and T2 [maintained with 2,4-D diet until PD 90]. Five to eight pups per age and sex were sacrificed at 6, 15, 30, 45 or 90 days of age for membrane receptor binding assays employing [3H]nemonapride. Subchronic 2,4-D exposure (T2 group) increased DA D2-type receptor around 40% in CPu. In addition, DA D2-type receptor levels also increased in PFc (15 and 30 days) and Cer (30 and 90 days). Sex-dependent differences in D2 receptors were observed with T2 female rats being more affected than T2 male rats. When the herbicide treatment was interrupted after weaning (T1 group), DA D2-type receptor density was apparently recovered and stabilized to control level. These findings suggest a reversible vulnerability of D2-type receptors to 2,4-D exposure. Regional increases of D2-type receptor density may explain certain behaviors reported early by us, such as catalepsy and right-turning preference in rats exposed to 2,4-D.

Astrocytic response in hippocampus and cerebral cortex in an experimental epilepsy model

Astrocytes are very sensitive to alterations in the brain environment and respond showing a phenomenon known as astroglial reaction. S100beta is an astroglial derived neurotrophic factor, seems to be involved in neuroplasticity. The aim of this work was to study the astrocytic response in rat hippocampus and cerebral cortex after repetitive seizures induced by 3-mercaptopropionic acid (MP) administration. Immunocytochemical studies were performed to analyze GFAP and S100beta expression. Both studied areas showed hypertrophied astrocytes with enlarged processes and increased soma size. Astrocyte hyperplasia was observed only in the cerebral cortex. A significant decrease in the astrocytic S100beta immunostaining occurs after MP treatment. These results indicate that MP administration induces an astroglial reaction with reduced intracellular S100beta level. The observed reduction in astroglial S100beta could be related to the release of this factor to the extracellular space, where it may produce neurotrophic or deleterious effects accordingly to the concentration achieved. The mechanism of this remains to be elucidated.

Altered neuron-glia interactions in a low, chronic prenatal ethanol exposure

Serotoninergic neurons, astrocytes and nitrergic system play an important role in central nervous system (CNS) development. These systems are altered in prenatal ethanol exposure (PEE) but ethanol (EtOH) effects may be very diverse under different conditions. In this study, we analyzed morphologically two serotoninergic mesencephalic nuclei and three prosencephalic areas of serotoninergic innervation in a model of pre- and postnatal low-ethanol exposure. Female Wistar rats were orally exposed to EtOH 6.6% (v/v), ad libitum, for 6 weeks before mating and during gestation and lactation while control group received water ad libitum. Twenty-day-old offspring (P21) brains were processed and immunoreactivity (IR) using antibodies against tryptophan hydroxylase (TPH), 5-HT, 5-HT transporter (5HTT), glial fibrillary acidic protein (GFAP), S-100B protein, 200-kDa neurofilaments (Nf-200) and neuronal nitric oxide synthase (nNOS) was evaluated. Dorsal and median raphe nucleus (DRN and MRN), hippocampus (Hipp), striatum (Strt) and frontal cortex (FCx) were studied by computer-assisted image analysis. Relative optical density (ROD) of TPH-IR, 5-HT-IR and nNOS-IR neurons; cell area of GFAP-IR astrocytes; relative area of 5HTT-IR fibers and Nf-200-IR were evaluated. TPH-IR was increased in DRN and MRN and 5-HT-IR was increased only in MRN. 5-HTT-IR fibers and ROD of S-100B-IR astrocytes were increased in the three prosencephalic areas while GFAP-IR astrocytes were hypertrophied only in Hipp and FCx. Nf-200 expression was increased in Hipp and Strt and morphologically altered in the FCx. ROD of nNOS-IR neurons was increased in Strt and FCx but was not detected in Hipp. We have also detected morphological changes resembling accelerated development and maturation, and early aging. Considering the evidences of a close 5-HT-astroglial-NO relationship during CNS development the differential response of the studied regions is an interesting result that could be due to different gradients of development in the studied areas and/or different responses of those areas to the effects of a low pre- and postnatal ethanol exposure.

Iron, zinc and copper levels in brain, serum and liver of neonates exposed to 2,4-dichlorophenoxyacetic acid

The effects of 2,4-dichlorophenoxyacetic acid (2,4-D, 70 or 100 mg/kg dam's body weight) on iron (Fe), zinc (Zn) and copper (Cu) in brain, liver and serum of well-nourished and undernourished pups exposed through dam's milk were determined. Undernourishment produced a high Fe decrease (serum and brain) and a delay in weight gain similar to that produced by the highest dose of 2,4-D on well-fed pups. In the latter animals, copper was found to be the most altered ion, increasing its level in serum, liver and some brain areas and decreasing in whole brain. Zinc was the most affected ion in brain areas. Well-nourished pups lactationally exposed to 70 mg 2,4-D/kg dam's body weight altered neither their metal levels nor their body weight in any of the tissues studied. Undernourished pups were more vulnerable to the 2,4-D effect than well-nourished pups. Undernourished pups exposed to a lower 2,4-D dose showed a decrease in their body, brain and liver weight similar to well-fed animals exposed to 100 mg 2,4-D/kg. A noticeable decrease in liver L-tryptophan peroxidase activity by 2,4-D was also registered. This effect was higher in undernourished and 2,4-D-exposed pups. These results suggest that brain areas have a different susceptibility to the herbicide and that undernourishment produces a higher vulnerability to the herbicide and exacerbates the 2,4-D effect.

Induction of apoptosis in cerebellar granule cells by 2,4-dichlorophenoxyacetic acid

2,4-Dichlorophenoxyacetic acid (2,4-D) and derivatives are herbicides widely used in Argentina and other parts of the world. Exposure to 2,4-D, its ester and salt formulations, have been associated with a range of adverse health effects in humans and different animal species, from embryotoxicity and teratogenicity to neurotoxicity. In this work, we demonstrate that after 24 hs of treatment with 1 and 2 mM 2,4-D there is an induction of apoptosis in cerebellar granule cells (CGC) in culture. However, with 2 mM 2,4-D one population of CGC developed features of apoptosis while another appeared to die by necrosis. This process is associated with an increase in caspase-3 activity after 12 hs of treatment with the herbicide, which is preceded by cytochrome c release from the mitochondria. Treatment of CGC with 2,4-D appears to induce apoptosis by a direct effect on mitochondria producing cytochrome c release and consequently activation of caspase-3, being mitochondrial damage sufficient for triggering the events that may cause apoptosis.

Environmental chemical compounds could induce sensitization to drugs of abuse

Chemical environment should be considered as an additional factor that influences drugs of abuse. Besides, maternal exposure to environmental chemicals has increased, and fetuses as well as neonates may be at greater risk than adults. Studies from our laboratory have described a permanent effect of the worldwide use of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) on serotonin and dopamine content in total brain and specific brain areas of adult rats born of mothers treated during lactation and fed with 2,4-D-treated diet after weaning. These animals show a modified neurotransmitter-related behavioral pattern in their developmental young and in adult age. Drugs that could be used to challenge the dopaminergic or serotoninergic systems include amphetamine or haloperidol, a postsynaptic dopamine receptor blocker. 2,4-D-exposed animals showed exacerbated response to challenges. Postnatal alterations in central dopaminergic and serotoninergic systems due to environmental chemical exposure may contribute to the enhanced/reduced behavioral sensitization to drugs of abuse.

Increased sensitivity in dopamine D(2)-like brain receptors from 2,4-dichlorophenoxyacetic acid (2,4-D)-exposed and amphetamine-challenged rats

To determine whether the dopamine D(2) receptor plays a crucial role in chemically acquired sensitivity to drugs of abuse like amphetamine (AMPH) after an exposure to aryloxoalkanoic compounds, we examined in the present work the impact of AMPH (10 mg/kg, i.p.) on the dopaminergic D(2)-like receptors. Rats were exposed to 2,4-D 70 mg/kg/day from gestation day (GD) 16 to postnatal day (PND) 23. After weaning, the pups were assigned to one of the two subgroups: T1 (fed with untreated diet until PND 90) and T2 (maintained with 2,4-D diet until PND 90). After that, an acute challenge with AMPH was administered to each animal. Rats were sacrificed at 0, 5, 24, 72, and 168 h after AMPH, and membranes of striatum (CPu), prefrontal cortex (PfC), hippocampus (H), and cerebellum (Ce) were obtained. Binding studies employing [(3)H]nemonapride showed that AMPH caused an increase in DA D(2)-like receptors of all brain areas between 5 and 24 h after the treatment, with a reduction to the basal levels one week later. The AMPH challenge to (T1 and T2) 2,4-D-exposed rats showed an alteration on receptor density depending on brain area and on sex, more than on the 2,4-D exposure time. This D(2)-like receptor density increase could explain the exacerbated behaviors of the 2,4-D-exposed and amphetamine-challenged animals, as previously observed by us. The withdrawal of 2,4-D did not produce a real reversion to basal levels of D(2)-like receptors, indicating that herbicide exposure during the preweanling period caused a sensitization and a stable DA D(2)-like receptor increase that was elicited when the system was challenged with this dopaminergic drug.

Effects of chronic maternal ethanol exposure on hippocampal and striatal morphology in offspring

Astrocytes and serotoninergic neurons play a role in central nervous system (CNS) development, probably through serotonin (5HT) stimulation of the glial 5HT(1A) receptor. Activation of 5HT(1A) receptors causes the release of S-100 beta, a glial derived growth factor. In vitro, astrocytes are profoundly altered by chronic maternal ethanol exposure (CMEE). CMEE is also associated with reduced 5HT brain levels and abnormal development of the serotoninergic system. In the present study we analyzed the hippocampal and striatal serotoninergic innervation and astroglial cells in the offspring of CMEE mothers. Female Wistar rats were orally exposed to ethanol 6.6% (v/v) ad libitum for 6 weeks before breeding and during gestation. After parturition, rat mothers continued receiving ethanol until pups reached 21 days old. The control group received water ad libitum. Rat offspring brains were processed by immunocytochemistry using antibodies directed to GFAP, serotonin transporter (5HTT), or S-100 beta protein. Hippocampus and striatum were studied by computer-assisted image analysis. Cell area of GFAP(+) astrocytes, surface of 5HTT(+) fibers per area unit, and relative optical density (ROD) of S-100 beta(+) astrocytes were measured and statistically processed. Our results show that astroglial GFAP was increased (astrocytes were hypertrophied) and 5HTT(+) fibers were increased in both the hippocampal CA-1 area and the striatum. On the other hand, S-100 beta ROD was increased only in the hippocampal CA-1 area but not in the striatum. The different response of the studied regions is an interesting result considering evidence of a close 5HT/astroglial relation during CNS development. These differences could be due to different gradients of development in the studied areas and/or different responses of those areas to the effect of maternal ethanol exposure since the first stages of embryonic development.

Alcohol exposure during adulthood induces neuronal and astroglial alterations in the hippocampal CA-1 area

Ethanol (ETOH) exposure can result in neuronal damage. Astrocytes are morphologic and functionally related to neurons, and astrocyte-neuron interactions provide strategic sites for the actions of many chemical compounds. The aim of the present work was to study the morphologic alterations of glial cells and neurons on the hippocampus after long-term ETOH exposure using GFAP and S-100 beta protein, neurofilaments of 200 kDa (Nf200), MAP2, and serotonin transporter (5HT-T) immunocytochemical staining. Adult Wistar male rats (200-250 g) were orally exposed to ETOH (6.6% v/v ad libitum) for 6 weeks. Control rats received water ad libitum. Brain sections from control and exposed rats were processed by immunocytochemistry. After ETOH exposure we observed in the CA1 area of the hippocampus: (1) an important astroglial reaction evidenced by the presence of GFAP(+) reactive astrocytes; (2) an increase in S-100 beta immunostaining in astroglial cells; and (3) a decrease in Nf200, 5HT-T, and MAP2 immunoreactivity. The current study provides evidence that long-term ETOH exposure induces alterations in the neuronal cytoskeleton and an astroglial reaction, which is a common response to brain injury and may promote functional recovery of the nervous system, as by the release of glial-derived trophic factors (such as S-100 beta) that promote cell survival and neurite growth.

Morphological study of 5-HT neurons and astroglial cells on brain of adult rats perinatal or chronically exposed to 2,4-dichlorophenoxyacetic acid

2,4-D is a chlorophenoxyherbicide used worldwide. We have studied the morphological alterations of 5-HT neurons and glial cells in the mesencephalic nuclei of adult rats exposed to 2,4-D both perinatally (during pregnancy and lactation) and chronically (during pregnancy, lactation and after weaning) with quantitative methods. Pregnant rats were daily exposed to 70 mg/kg of 2,4-D from gestation day (GD) 16 to post-natal day (PND) 23 through diet. After weaning, pups were assigned to one of two sub-groups: T1 (fed with untreated diet until PND 90) and T2 (maintained with 2,4-D diet until PND 90). Brain sections were immunocytochemically stained using polyclonal anti-5-HT, anti-GFAP and anti-S-100 protein antibodies as cells markers. 2,4-D exposure during pregnancy and lactancy (T1 group) produced an increase in 5-HT neuronal area and immunoreactivity (IR) in the mesencephalic nuclei studied. However, with the chronical 2,4-D exposure (T2 group) only the 5-HT neuronal area from the dorsal raphe nucleus (DRN) was increased, suggesting an adaptable response of 5-HT neurons in median raphe nucleus (MRN). The presence of reactive astrocytes in mesencephalic nuclei and in hippocampus were also different for the two 2,4-D exposure designs, showing the existence of a correspondence between neuronal changes and astrogliosis. Results support evidences that 2,4-D alters the serotoninergic system and that 5-HT neurons of each mesencephalic nuclei show different responses to the 2,4-D exposure designs which are parallel to astrogliosis.

Intracerebral administration of 2,4-diclorophenoxyacetic acid induces behavioral and neurochemical alterations in the rat brain

Although, the mechanism of 2,4-dichlorophenoxyacetic acid (2,4-D) neurotoxicity remains unknown, the monoaminergic system appears to mediate some of its effects in rats as we previously reported. In this study; we examined the 2,4-D effects on locomotor activity, circling behavior and monoamine levels after the injection into the basal ganglia of male adult rats. These effects were compared with those induced after selective lesions of dopaminergic neurons with 6-hydroxydopamine (6-OHDA). 2,4-D-injected into one striatum (100 microg/rat) produced a marked depression in locomotor activity and elicited a moderate circling towards the ipsilateral side at 6 and 24 h postinjection. These behavioral changes were accompanied by a decrease and an increase of serotonin (5-HT) and homovanillic acid (HVA) levels, respectively. 2,4-D administration (100 microg/rat) into the nucleus accumbens, induced similar behavioral and neurochemical patterns to the intrastriatal 2,4-D injection, although rats did not present notorious turning. When 2,4-D was injected into one medial forebrain bundle (MFB, 50 microg/rat), animals presented ipsilateral circling, while locomotor activity was unchanged at 3 and 7 days post-injection. These last rats also exhibited diminished levels of striatal 5-HT, dopamine (DA) and their metabolites without changes in the substantia nigra (SN). Animals sacrificed 3 and 7 days after a 6-OHDA injection into one of the MFB, presented progressive depletion of dopamine in striatum and SN. 2,4-D as well as 6-OHDA-treated rats into one of the MFB were challenged with low dose (0.05 mg/kg s.c.) of apomorphine (only at 7 days post-injection) to evaluate a possible DA-receptor supersensitivity. Only 6-OHDA treated rats showing a vigorous contralateral rotation activity. These results indicate that 2,4-D induced a regionally-specific neurotoxicity in the basal ganglia of rats. The neurotoxic effects of 2,4-D on basal ganglia by interacting with the monoaminergic system depended not only on the exact location of the 2,4-D injection, but also on the dose and time period of post-injection. Toxicity produced by 2,4-D appears to be different in monoaminergic terminals, axonal fibers, and cell bodies.

Behavioral alterations induced in rats by a pre- and postnatal exposure to 2,4-dichlorophenoxyacetic acid

The purpose of this study was to determine whether the behavioral development pattern was altered by a pre- and postnatal exposure to 2,4-Dichlorophenoxyacetic acid (2,4-D). Pregnant rats were daily orally exposed to 70 mg/kg/day of 2,4-D from gestation day (GD) 16 to postnatal day (PND) 23. After weaning, the pups were assigned to one of the two subgroups: T1 (fed with untreated diet until PND 90) and T2 (maintained with 2,4-D diet until PND 90). Effects on offsprings were evaluated with a neurotoxicological test battery. Neuromotor reflexes, spontaneous motor activity, serotonin syndrome, circling, and catalepsy were analyzed during various postnatal ages. 2,4-D neonatal exposure induced delay of the ontogeny of righting reflex and negative geotaxis accompanied by motor abnormalities, stereotypic behaviors (excessive grooming and vertical head movements), and hyperactivity in the open field. Adult rats of both sexes (T2 group) showed a diminution of ambulation and rearing, while excessive grooming responses were only observed in T2 males. Besides, these animals manifested serotonin syndrome behaviors, catalepsy, and right-turning preference. Some behaviors were reversible, but others were permanent, and some were only expressed after pharmacological challenges.

Neural and astroglial effects of a chronic parachlorophenylalanine-induced serotonin synthesis inhibition

Serotonin (5HT) is one of the classical neurotransmitters expressed earlier in the embryonic rat brain, and it was proposed as a developmental signal in the central nervous system. In the adult brain, 5HT seems to be involved in neuronal plasticity. It was postulated that S-100 protein, a glial neurotrophic factor, could be modulated by 5HT probably through the glial 5HT1A receptors. In a model of chronic inhibition of endogenous 5HT synthesis produced by the daily administration of parachlorophenylalanine (PCPA) for 2 wk, we have studied by immunohistochemical methods and digital morphometric analysis the expression of two proteins present in rat brain astrocytes: glial fibrillary acidic protein (GFAP) and S-100 protein. The effectiveness of the PCPA treatment was tested by the use of specific anti-5HT antibodies that showed absence of 5HT fibers in 5HT innervation areas like frontal cortex and hippocampus. Different effects of PCPA treatment on serotoninergic raphe nuclei were observed: dorsal raphe nucleus (DRN) seemed to be more sensitive to the PCPA's action than ventral raphe nucleus (VRN). In DRN and in the two 5HT innervation areas studied, glial cells responded to the 5HT depletion induced by PCPA showing astrocytes with large and tortuous processes. Astrocytes from 5HT-depleted regions showed higher immunostaining for S-100 protein than controls. There was not any modification in optical density of S-100 protein immunostaining in VRN, the area less sensitive to PCPA treatment. These observations indicated that astrocytes are sensitive to the 5HT level, and in presence of low 5HT concentration in the intercellular space, astrocytes could react by synthesizing glial proteins like GFAP and S-100 protein.