Biomedical subjects

D W Walker

Publications and source records attributed to D W Walker.

At least 55 records · Page 3Linked to original sources

PubMed1998

Effects of neonatal ethanol exposure on cholinergic neurons of the rat medial septum.

The objective of this study was to determine the long-term effects of neonatal ethanol exposure on the cholinergic neurons in the medial septum (MS) of the rat. On postnatal day 4 (P4) pups were assigned to one of three groups: an ethanol-receiving, gastrostomized group (EtOH); a pair-fed, gastrostomized control group (GC); and a dam-reared suckle control group (SC). Gastrostomized pups were infused with ethanol-containing or control diet as a 9.1% v/v solution for two feedings on each day from P4 to P10. Choline acetyltransferase (ChAT) immunocytochemistry was analyzed at P60. Ethanol treatment resulted in long-lasting microencephaly in P60 EtOH animals. Ethanol exposure did not directly reduce ChAT-expressing (ChAT+) neuronal number, nor were changes noted in MS volume, mean area/section, or cell density as a result of ethanol treatment. Ethanol exposure reduced ChAT+ neuronal size in EtOH males compared with GC males but not SC males. No differences in ChAT+ neuronal size were noted in females. Thus, neonatal ethanol exposure, whereas producing long-lived microencephaly, has little effect on the cholinergic neurons of the adult rat MS.

Animals↗

PubMed1998

Oligonucleotide inhibitors of P-selectin-dependent neutrophil-platelet adhesion.

P-selectin, an inducible cell adhesion molecule, mediates rolling of neutrophils on activated vascular endothelium. Because rolling is an early event of the inflammatory response, therapeutic applications of selectin antagonists have been of broad interest. There are, however, no truly satisfactory therapeutic candidates among known inhibitors. Consequently, we have used Systematic Evolution of Ligands by Exponential Enrichment (SELEX) technology, a process based on oligonucleotide combinatorial chemistry and in vitro selection, to develop aptamer antagonists of P-selectin. Equilibrium dissociation constants for aptamer/P-selectin binding range from 16 to 710 pM, a 10(5)-10(6)-fold improvement compared with the minimal carbohydrate ligand, sialyl Lewis X (sLeX). Aptamer binding is divalent cation dependent and, unlike sLeX, is specific for P-selectin. The selectivity for human P-selectin relative to human E-selectin or human L-selectin is 10(4)-10(5). In vitro, aptamers bind with subnanomolar affinities to P-selectin expressed on thrombin-activated platelets, inhibit the binding of P-selectin-IgG chimera to sLeX and to neutrophils, and block the binding activated platelets to neutrophils in flow cytometry and in hydrodynamic assays. Extrapolating from their in vitro characteristics, these novel P-selectin-specific antagonists may be suitable candidates for therapeutic development.

Base Sequence↗

PubMed1998

Physiological evidence for arteriovenous anastomoses in the uterine circulation of late-pregnant ewes.

1. The objective of the present study was to determine whether arteriovenous anastomoses (AVA) are present in the uterine circulation of conscious, late-pregnant ewes. 2. Twenty late-pregnant ewes were assigned to two groups. In group 1, 15 microm coloured microspheres were injected into the uterine artery of the pregnant horn and the relative proportion of microspheres trapped in the uterus and lungs was determined. The percentage shunting of blood measured by this method was 17+/-3%, representing a blood flow of 164+/-39 mL/min (n = 12). Any contribution of ovarian, cervical, rectal and other vascular beds was specifically excluded in this group. 3. In group 2, total uterine capillary flow was measured using the reference blood flow method, by injecting 15 microm microspheres into the heart. Calibrated flow probes, placed on both main uterine arteries, concurrently measured total uterine blood flow. Total blood flow to the uterus (flow probe) was significantly greater (t = 3.415; P = 0.027) than uterine capillary flow (microspheres), indicating AVA shunting in the uterine circulation. Mean total blood flow to the uterus was 1749+/-160 mL/min, of which an average 25+/-5% (n = 5 sheep) was shunted. 4. The percentage AVA shunting for groups 1 and 2 was not significantly different (t = 1.219; P = 0.24) and, when combined, the mean percentage of uterine blood flow passing through AVA in the late-pregnant sheep was determined to be 19+/-3%. 5. The present study shows that AVA are present and patent in the uterine circulation of late-pregnant ewes and that they account for the shunting of approximately 20% of the uterine blood flow into the maternal venous circulation.

Animals↗

PubMed1998

The effect of prenatal exposure to carbon monoxide on breathing and growth of the newborn guinea pig.

In utero hypoxia may affect the development of the brain and result in altered respiratory responses postnatally. Using a barometric plethysmograph, we examined the effects of exposing pregnant guinea pigs to 200 ppm carbon monoxide (CO) for 10 h/d from d 23-25 of gestation until term (approximately 68 d) on the ventilatory responses of their 4-5-d-old neonates at rest, and during progressive asphyxia and steady state hypercapnia. Exposure to this concentration of CO produced significantly higher levels of carboxyhemoglobin (COHb) in maternal (8.53 +/- 0.6% versus 0.25 +/- 0.1%) and fetal blood (13.0 +/- 0.4% versus 1.6 +/- 0.1%) from CO-treated animals when compared with controls. Hematocrit was significantly higher in the CO-treated neonates (46.3 +/- 1.0% versus 41.3 +/- 0.9%) at 5-6 d of age, although no difference existed between the groups for COHb at this time. There was no difference between the groups for length of gestation, litter size, or birth weight, but CO-treated neonates were significantly smaller at 4 d of age (102.4 +/- 3.7 g) compared with controls (132.0 +/- 5.0 g). At 4-5 d of age there was no difference between the groups for either tidal volume (VT), respiratory frequency (f), or minute ventilation (VE) at rest, but during steady state hypercapnia (4 and 6% CO2) the CO-treated neonates had a significantly greater VT and VE (but not f) than did controls. During progressive asphyxia, CO-treated animals had a significantly greater VT than did controls from 1-8% CO2. There was a significant fall in f at 1 and 3% CO2 in CO-treated animals; however, this effect did not persist, resulting in a significantly increased VE from 3 to 8% CO2. The inspiratory flow rate (VT/expiratory time) was significantly increased in the CO-treated neonates during progressive asphyxia; this occurred in the absence of a difference in inspiratory time between the groups. These results indicate that prenatal exposure to CO increases CO2 sensitivity in 4-5-d-old guinea pigs. This may be due to developmental alterations in the areas of the brainstem responsible for respiratory control.

Animals↗

PubMed1998

Dynamic changes in arousal threshold during sleep in the human infant.

Failure to arouse from sleep is a possible mechanism leading to sudden infant death. Using a controlled pulsatile air jet applied alternately to the nostrils we have made multiple measures of arousal threshold both between and within sleep states. Infants (n = 22) born at term were studied at 2-3 wk postterm (mean age 13 d, range 9-17 d, study 1) and again at 2-3 mo postterm (mean age 78 d, range 56-98 d, study 2). Arousal threshold (stimulus driving pressure, cm H2O) was determined in both active sleep (AS) and quiet sleep (QS). At both ages arousal threshold in QS was significantly higher (251 +/- 24 and 298 +/- 35) than in AS (163 +/- 19 and 144 +/- 29) (p < 0.001). In a morning sleep period, the first and second QS epochs were compared in each baby. In both study 1 and study 2, respectively, arousal thresholds were significantly higher in the second QS epoch (270 +/- 34 and 497 +/- 100) than in the first QS epoch (198 +/- 29 and 252 +/- 69) (p < 0.05 and p < 0.02). There was a significant correlation in individual infants between arousal thresholds in the two states at both ages (p < 0.005 and p < 0.007, respectively). Regression analysis showed no correlation between the length of time the infant had been in a particular sleep state and the arousal threshold in either state in study 1 or in AS in study 2; however, arousal threshold increased significantly (p < 0.01) with time in QS in study 2. This study has expanded on previous findings that arousability is sleep state-dependent by demonstrating that arousability in QS is also altered by the length of time that the infant has been asleep.

Activity Cycles↗

PubMed1998

A relationship between thermotolerance and longevity in Caenorhabditis elegans.

Studies of aging in the nematode Caenorhabditis elegans have revealed a relationship between stress resistance and the rate of aging: Mutations which extend mean and maximum life-span also confer resistance to thermal stress. We review the molecular genetics of aging in C. elegans and introduce methods for obtaining novel mutants which display altered aging rates. We present the use of the "surrogate" phenotype of thermotolerance to develop a selection for novel mutations which slow aging.

Adaptation, Physiological↗

PubMed1997

Cultured postnatal rat septohippocampal neurons change intracellular calcium in response to ethanol and nerve growth factor.

Ethanol exposure affects cellular mechanisms involved in the regulation of calcium (Ca2+) homeostasis. Neurotrophins, such as nerve growth factor (NGF), stabilize intracellular Ca2+([Ca2+]i) during a variety of neurotoxic insults. In this study, changes in [Ca2+]i during treatment with ethanol and NGF were measured at the cell body of neurons using the Ca2+ indicator indo-1. Cultured postnatal day-of-birth (P0) septohippocampal (SH) neurons that were labeled with 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanine perchlorate (DiI), increased [Ca2+]i in response to ethanol. This response was dose-related. P0 SH neurons treated with NGF had lower [Ca2+]i than neurons withdrawn from NGF, implying that NGF may modulate Ca2+ homeostasis in these neurons. NGF also prevented the dose-related increase in [Ca2+]i in ethanol-treated SH neurons. The SH neurons increased [Ca2+]i when they were stimulated with 30 mM potassium chloride (KCl). Ethanol inhibited the potassium-stimulated change in [Ca2+]i but the combination of ethanol and NGF caused [Ca2+]i to increase with 100 mg% and 400 mg% ethanol and to decrease to a lower level with 200 mg% ethanol. These data were compared to data from previously published similar aged medial septal (MS) neurons (B. Webb, S.S. Suarez, M.B. Heaton, D.W. Walker, Clin. Exp. Res. 20 (1996) 1385-1394) and with embryonic gestational day 21 (E21) SH neurons (B. Webb, S.S. Suarez, M.B. Heaton, D.W. Walker, Brain Res. 729 (1996) 176-189). Differences in [Ca2+]i responses were observed in ethanol and NGF-treated postnatal SH neurons compared with P0 MS neurons and E21 SH neurons. Of these differences, most occurred during the combined treatment with ethanol and NGF compared with either treatment alone.

Animals↗

PubMed1997

Neurochemical basis of disruption of hippocampal long term potentiation by chronic alcohol exposure.

The aim of this review is to summarize the possible mechanisms underlying the long-term impairment of learning and memory resulting from chronic ethanol treatment (CET) especially that involving decrements in long-term potentiation (LTP) in hippocampus. CET for a 28-week duration affects the rat hippocampal formation in such a way as to decrease the magnitude of LTP; an effect that can last as long as 7 months after ethanol withdrawal. It appears that NMDA receptor number in hippocampus is unchanged after CET whereas the data suggest a more pronounced role for changes in GABAergic and cholinergic synaptic transmission in determining how CET influences the induction of LTP in hippocampus. In particular, changes in presynaptic modulation of neurotransmitter release in hippocampus may be one mechanism by which CET inhibits LTP. Thus, the mechanisms underlying the effect of CET on LTP are a result of changes in a number of neurotransmitter systems in hippocampus (GABAergic and cholinergic) rather than based solely on changes in glutamate transmission.

Acetylcholine↗

PubMed1997

Gammahydroxybutyrate (GHB) receptor ligand effects on evoked synaptic field potentials in CA1 of the rat hippocampal slice.

GHB produced a concentration-dependent depression of evoked synaptic field potentials (EFPs) recorded extracellularly in the CA1 region of the in vitro rat hippocampal slice. The concentration/response function revealed a threshold near 1 mM, with IC50 of 10.85 mM and a Hill coefficient of 1.29. The gamma-aminobutyric acid B-receptor (GABA-B) agonist baclofen also depressed the EFP, but even maximally effective concentrations of the GABA-B antagonist 2-hydroxy-saclofen (800 microM) could not completely block the GHB-induced EFP depression. Nor was GHB-induced EFP depression blocked by the GHB receptor "antagonist" NCS-382, which does not displace GABA-B receptor ligands. However, NCS-382 produced a concentration-dependent increase in EFP slope. The threshold concentration was about 100 microM but the maximally effective concentration, and thus the IC50, could not be determined in the perfusion slice system. NCS-382 may be an inverse agonist at hippocampal GHB receptors, or else endogenous hippocampal GHB receptor ligands medicate a tonic inhibition in CA1. At concentrations sufficient to induce EFP depression GHB did not alter pH. Although isosmotic sucrose did depress CA1 EFPs it was essentially ineffective at the IC50 for GHB. Gamma-butyrolactone, a prodrug of GHB, was only 1/20th as effective as GHB. This is consistent with previous data suggesting that GBL is freely permeable (does not substantially disturb tonicity) and that brain has very little capacity to either enzymatically convert the lactone to GHB or respond to the lactone itself.

Animals↗

PubMed1997

Suppression of arousal by progesterone in fetal sheep.

The high rate of progesterone synthesis by the placenta in late gestation exposes the ovine fetus to high concentrations of progesterone and its metabolites that may affect activity of the fetal brain. The aim of this study was to determine the effect of inhibiting maternal progesterone synthesis on sleep-wake activity in fetal sheep. Fetal and maternal vascular catheters, a fetal tracheal catheter, and electrodes for recording fetal electrocortical (ECoG), electro-ocular (EOG) and nuchal muscle electromyographic (EMG) activity were implanted. At 128-131 days gestation, progesterone production was inhibited by an injection of trilostane (50 mg), a 3beta-hydroxysteroid dehydrogenase inhibitor. Vehicle solution or progesterone (3 mg h(-1)) was then infused into the ewe between 6 and 12 h after the trilostane treatment. Maternal progesterone concentrations were significantly reduced from 1-24 h after trilostane treatment (P < 0.05) when followed by vehicle infusion. Fetal breathing movements (FBM), EOG, nuchal muscle EMG, and behavioural arousal increased 12 h after trilostane treatment (P < 0.05). In contrast, there was no change in fetal arousal, EOG, EMG or FBM activities when progesterone was infused after the trilostane treatment. These findings show that progesterone can influence fetal behaviour, and indicates that normal progesterone production tonically suppresses arousal, or wakefulness in the fetus.

3-Hydroxysteroid Dehydrogenases↗

PubMed1997

Effects of prenatal ethanol exposure on parvalbumin-expressing GABAergic neurons in the adult rat medial septum.

Exposure of human fetuses to ethanol often results in the fetal alcohol syndrome. Animal models of fetal alcohol syndrome have been developed and used to examine the consequences of prenatal ethanol exposure on the central nervous system. The objective of this study was to determine the long-term effects of prenatal ethanol exposure on parvalbumin-expressing (PA+) GABAergic neurons of the rat medial septum. Pregnant Long-Evans rats were maintained on 1 of 3 diets from gestational day 0 to 21: an ethanol-containing liquid diet in which ethanol accounted for 35% of the total calories, a similar diet with the isocaloric substitution of sucrose for ethanol, or a lab chow control diet. Offspring were killed on postnatal day 60, and their brains were prepared for parvalbumin immunocytochemistry. Female rats exposed to the ethanol-containing diet during gestation had 42% fewer PA+ neurons in the medial septum and reduced PA+ cell density when compared with female rats exposed to the sucrose diet. Ethanol females also had fewer PA+ neurons per unit volume than sucrose females. Male rats exposed to ethanol did not display a similar reduction in PA+ neurons or density. No effect of prenatal diet was found on the area or volume of the medial septum, nor were cell diameters affected. As such, prenatal exposure to ethanol seems to reduce permanently the number of PA+ neurons in the female rat medical septum without affecting area, volume, or neuronal size. Functional implications and possible relations to the fetal alcohol syndrome are discussed.

Animals↗

PubMed1997

Effects of chronic ethanol exposure on GABA receptors and GABAB receptor modulation of 3H-GABA release in the hippocampus.

Chronic ethanol treatment (CET), sufficient for decreasing long-term potentiation (LTP) in rats, also enhances 3H-GABA release from hippocampal slices in these same animals. The mechanism for an increase in GABA release may involve changes in presynaptic receptors. Therefore, we characterized presynaptic autoreceptor modulation of 3H-GABA release in hippocampal slices from control and CET rats. The effects of a GABAB receptor agonist (baclofen) and antagonist [2-hydroxy (OH)-saclofen] were tested for their ability to modulate electrically stimulated 3H-GABA release from superfused hippocampal slices. Baclofen decreased stimulated release in a dose-dependent manner and 2-OH-saclofen increased release consistent with the existence of presynaptic GABAB autoreceptors in hippocampus. The GABAA antagonist bicuculline did not significantly modulate basal or stimulated release. When the effects of baclofen and 2-OH-saclofen were measured in animals 48 hr after withdrawal from CET, presynaptic modulation of release by baclofen and 2-OH-saclofen was decreased. In addition, we examined the density of 3H-baclofen and 3H-bicuculline binding in the hippocampal formation using quantitative autoradiographic techniques. We found that the density of 3H-baclofen binding sites was not affected by CET, whereas the density of 3H-bicuculline binding sites was increased by 28% in ethanol-treated rats. These data may explain how CET increases presynaptic regulation of GABA release from hippocampus that may contribute to the decrease in LTP seen in rats after CET.

Alcoholism↗

PubMed1997

NMDA receptor binding in adult rat brain after several chronic ethanol treatment protocols.

The amino acid L-glutamate is a major excitatory neurotransmitter that is involved in many CNS functions, including learning, memory, long-term potentiation, and synaptic plasticity. Acute exposures to ethanol (50 to 200 mM) have been shown to inhibit NMDA receptor responses, whereas chronic exposure to ethanol leads to adaptive supersensitivity thought to be involved in ethanol dependence and tolerance. To investigate the effects of chronic ethanol exposure on glutamate receptor density, we examined the binding of both NMDA and non-NMDA ligands in rat brain after several chronic ethanol treatment protocols using a number of different rat strains. No increases in the binding of [3H]MK-801, [3H]CGP 39653, or the polyamine specific competitive antagonist, [3H]ifenprodil, were seen after two well-used chronic ethanol treatments. These included the 2-week liquid diet developed by Frye et al. (J. Pharmacol. Exp. Ther. 216:306-314, 1981) and the 4-day binge treatment developed by Majchrowicz (Psychopharmacologia 43:245-254, 1975). However, small increases in the binding of both the NMDA noncompetitive antagonist [3H]MK-801, as well as the competitive NMDA antagonist [3H]CGP 39653, were seen in select frontal brain regions after 3 weeks of the Walker-Freund chronic ethanol liquid diet. When this chronic liquid diet treatment was extended to a period of 6 weeks, these increases in receptor binding were diminished to nonsignificant levels. The binding of the non-NMDA ligands [3H]AMPA and [3H]kainate were not significantly affected by either length of Walker-Freund liquid diet exposure. When rats were treated chronically with ethanol for 30 days using the paradigm developed by Tsukamoto et al. (Hepatology 5:224-232, 1985), small, but significant, increases in the binding of [3H]MK-801 were seen in the CA1 and dentate gyrus regions of the hippocampus. These studies indicate that robust increases in NMDA receptor binding do not occur with several chronic ethanol treatment protocols, and suggests that NMDA receptor supersensitivity during the development of tolerance and dependence to ethanol may not simply be due to changes in the density of NMDA receptors, but may involve other mechanisms.

2-Amino-5-phosphonovalerate↗

PubMed1997

Ethanol effects on cultured embryonic hippocampal neuronal calcium homeostasis are altered by nerve growth factor.

The neurotoxic effect of acute ethanol treatment (AET) may lead to an alteration in the regulation of calcium (Ca2+) homeostasis in hippocampal neurons. Ca2+ homeostasis could be affected by AET when neurons are at rest or after depolarizing activity during synaptic transmission. It has been shown that nerve growth factor (NGF) can ameloriate some types of neurotoxicity by stabilizing Ca2+ homeostasis. Previously, we observed that ethanol (EtOH) changed unstimulated (basal) and potassium (K+)-stimulated intracellular calcium ([Ca2+]i) in embryonic septohippocampal neurons (Webb et al., Brain Res. 729:176-189, 1996). The purpose of the present study is to determine the effects of NGF and EtOH on neuronal Ca2+ homeostasis in cultured embryonic hippocampal neurons. The hypotheses tested were the following: EtOH alters Ca2+ homeostasis in hippocampal neurons; NGF modulates Ca2+ homeostasis in hippocampal neurons; and NGF treatment alters the effect of EtOH on [Ca2+]i in hippocampal neurons. Our results indicated that hippocampal neuronal cultures treated with EtOH had lower basal [Ca2+]i than untreated neurons. EtOH decreased K+-stimulated (30 mM KCI) changes in [Ca2+]i in a dose-dependent manner. During K+ stimulation, 20 ng/ml of NGF slowed and reduced the increase in [Ca2+]i. Hippocampal neurons treated with NGF increased or did not change basal [Ca2+]i and did not change or increase K+-stimulated [Ca2+]i in response to EtOH. These responses were dose-related and indicated that NGF could alter the response of hippocampal neurons to EtOH. In conclusion, AET results in the alteration of Ca2+ homeostasis in unstimulated and depolarized cultured embryonic hippocampal neurons. NGF and EtOH independently and collectively affected the regulation of Ca2+ homeostasis in this neuronal population. Changes in [Ca2+]i can disrupt normal cellular function and contribute to cell death. Therefore, alteration of Ca2+ homeostasis may be an underlying mechanism involved in EtOH toxicity. NGF may ameliorate the toxic effects of EtOH by regulating Ca2+ homeostasis.

Animals↗

PubMed1996

Calcium homeostasis in cultured embryonic rat septohippocampal neurons is altered by ethanol and nerve growth factor before and during depolarization.

Ethanol and nerve growth factor (NGF) affect the survival of septohippocampal (SH) neurons. The effect of ethanol and NGF on calcium (Ca2+) homeostasis in these neurons was investigated in this study. Changes in intracellular-free Ca2+ concentration ([Ca2+]i) were measured using indo-1 in cultured embryonic (E21) SH neurons before stimulation (basal) and during stimulation with 30 mM potassium cloride (KCl+). SH neurons were treated with 0, 100, 200, 400, or 800 mg% ethanol with NGF (+NGF) or without NGF (-NGF). NGF treatment decreased, while ethanol did not affect basal [Ca2+]i. The combination of ethanol and NGF treatment led to increases in basal [Ca2+]i. While [Ca2+]i was lower during stimulation with KCl+ following ethanol or NGF treatment, ethanol and NGF treatment together led to significantly greater increases or decreases in [Ca2+]i compared to similarly treated NGF neurons. Responses of SH neurons were compared to those of medial septal (MS) neurons. Changes in [Ca2+]i during treatment with ethanol and/or NGF were reduced in SH neurons compared with MS neurons. We conclude that changes in Ca2+ homeostasis can occur in SH neurons in the presence of ethanol and/or NGF. The changes following ethanol treatment are enhanced by NGF. By altering Ca2+ homeostasis, NGF may enhance the survival of SH neurons during ethanol-induced neurotoxicity.

Animals↗

PubMed1996

Influence of chronic prenatal ethanol on cholinergic neurons of the septohippocampal system.

This study characterized the influence of full-term gestational ethanol exposure on choline acetyltransferase (ChAT)-immunoreactive neurons that project to the hippocampus, within the medial septal (MS) nucleus and the vertical limb of the diagonal band of Broca (DBv). On gestation days 1-22, pregnant dams were fed either a vitamin fortified ethanol-containing liquid diet, pair fed a calorically equivalent sucrose-containing diet, or given rat chow ad libitum. In a previous study, we found that chronic prenatal exposure to ethanol, in this manner, resulted in a significant decline in the ontogenetic upregulation of ChAT activity in the septal area during the second postnatal week, but was followed by recovery to control levels by adulthood. On postnatal days 14 and 60 (P14 and P60) the brains were prepared for ChAT immunocytochemistry. Ethanol exposure had little influence on the number of ChAT-positive neurons in the MS nucleus of animals at either age. Ethanol exposure had no effect on neuronal size or ChAT staining intensity of MS or DBv neurons when compared to chow-fed offspring. Although age-related increases in cholinergic neuronal numbers and decreases in neuronal size were observed between juvenile and adult animals, prenatal ethanol exposure did not appear to influence these postnatal changes in the population as a whole. Overall, these findings suggest that the anatomical maturation of septal cholinergic neurons may be relatively insensitive to prenatal ethanol exposure under conditions of a vitamin-rich dietary supplementation, while biochemical development within this region may be more susceptible to early ethanol influences.

Animals↗

PubMed1996

Influence of prenatal ethanol exposure on cholinergic development in the rat striatum.

This study investigated the influence of ethanol exposure throughout gestation on cholinergic development within the rat striatal region. Pregnant Long-Evans rats were maintained on three diets throughout gestation: A liquid diet in which ethanol accounted for 35-39% of the total calories, a similar diet with the isocaloric substitution of sucrose for ethanol, and a lab chow control diet. At postnatal days 14 and 60 (P14 and P60), the striatal regions of the offspring were analyzed for the number of cholinergic neurons, via choline acetyltransferase (ChAT) immunostaining. The area of the striatum was also measured in these animals. At P14, P21, and P60, ChAT activity was assessed in the same region. These analyses revealed a significant increase in the number of cholinergic striatal neurons at P14 in the animals which had been exposed prenatally to ethanol. This increase was transient, however, with equal numbers of ChAT-positive cells found in all three groups by adulthood (P60). The brain weights of the ethanol-exposed animals were significantly reduced at P14 and P21, but were comparable to controls by P60. There were no significant differences in the striatal area or the overall volume of the region assessed, however, at either P14 or P60. Although there were some increases in ChAT activity across the ages viewed (most notably between P14 and P21), there were no effects of diet on ChAT activity at any age assessed. It is proposed that the increased numbers of cholinergic neurons could be a function of errors in migration, enhanced neurogenesis, diminished cell death, alterations in gene expression, or increased cell survival as a result of alterations in neurotrophic factor production or availability.

Age Factors↗

PubMed1996

Up-regulation of high-affinity neurotrophin receptor, trk B-like protein on western blots of rat cortex after chronic ethanol treatment.

We previously reported that the total neurotrophic activity of hippocampal extracts was significantly (25-50%) reduced after 21-28 weeks of chronic ethanol treatment (CET) [23]. To test whether the level of a neurotrophic factor (i.e., ligand itself) is compromised, we measured nerve growth factor (NGF) protein and NGF mRNA contents using ELISA and Northern analysis. We reported that CET did not appear to reduce NGF protein, NGF mRNA or total neurotrophic activity when measured on sympathetic ganglia neurons [4]. We also observed that both NT-3 mRNA and bFGF mRNA levels were unaffected, but the BDNF mRNA levels was significantly reduced in CET rat hippocampus [18]. Neuronal degeneration and reduction of total neurotrophic activity after CET appear to be induced, at least partially, by compromised transcription of BDNF gene. CET may also induce functional changes in receptors for the neurotrophic factors. To investigate possible changes in neurotrophic factor-receptors, we examined Western blots (immunoblots) of rat cortex after 28 weeks of CET. After sonication and ultra-centrifugation, the supernatant of crude lysates of the cortex from individual animals was subjected to SDS-PAGE, electrotransfered to nitrocellulose membrane, incubated with anti-trk B antibody and secondary antibody conjugated to alkaline phosphatase, and reacted with chemiluminescent substrate. The membranes were then exposed to Kodak XAR film. Compared to controls (n = 6), CET rats (n = 6) appeared to have significantly higher band intensity (P < 0.01) of trk B-like protein at about 145 kDa, which suggests an up-regulation of trk B-like proteins to compensate the compromised level of certain subset (i.e., BDNF or NT-4/5, but not NGF) of neurotrophins in cortex.

Alcoholism↗