Assessing disease severity in late infantile neuronal ceroid lipofuscinosis using quantitative MR diffusion-weighted imaging.

BACKGROUND AND PURPOSE: Late infantile neuronal ceroid lipofuscinosis (LINCL), a form of Batten disease, is a fatal neurodegenerative genetic disorder, diagnosed via DNA testing, that affects approximately 200 children in the United States at any one time. This study was conducted to evaluate whether quantitative data derived by diffusion-weighted MR imaging (DWI) techniques can supplement clinical disability scale information to provide a quantitative estimate of neurodegeneration, as well as disease progression and severity. MATERIALS AND METHODS: This study prospectively analyzed 32 DWI examinations from 18 patients having confirmed LINCL at various stages of disease. A whole-brain apparent diffusion coefficient (ADC) histogram was fitted with a dual Gaussian function combined with a function designed to model voxels containing a partial volume fraction of brain parenchyma versus CSF. Previously published whole-brain ADC values of age-matched control subjects were compared with those of the LINCL patients. Correlations were tested between the peak ADC of the fitted histogram and patient age, disease severity, and a CNS disability scale adapted for LINCL. RESULTS: ADC values assigned to brain parenchyma were higher than published ADC values for age-matched control subjects. ADC values between patients and control subjects began to differ at 5 years of age based on 95% confidence intervals. ADC values had a nearly equal correlation with patient age (R2=0.71) and disease duration (R2=0.68), whereas the correlation with the central nervous system disability scale (R2=0.27) was much weaker. CONCLUSION: This study indicates that brain ADC values acquired using DWI may be used as an independent measure of disease severity and duration in LINCL.

Up-regulation of dopamine D(2)L mRNA levels in the ventral tegmental area and dorsal striatum of amphetamine-sensitized C57BL/6 mice: role of Ca(v)1.3 L-type Ca(2+) channels.

Dopamine D(2) long (D(2)L) and D(2) short (D(2)S) isoforms of the D(2) receptor play an important role in psychostimulant-induced neuronal adaptations. In this study, we used quantitative real-time PCR to specifically amplify these two splice variants to examine their mRNA expression in the dorsal striatum (dStr), nucleus accumbens (NAc) and the ventral tegmental area (VTA) of amphetamine-sensitized C57BL/6 mice. We found a significant increase in D(2)L mRNA in the VTA and dStr of amphetamine-treated mice that positively correlated with the sensitized locomotor response. We also found a significant increase in D(2)S mRNA in the VTA. We further examined the role of the Ca(v)1.3 subtype of L-type Ca(2+) channels in up-regulation of D(2)L and D(2)S mRNA in the VTA. Amphetamine-pretreated Ca(v)1.3 wild-type (Ca(v)1.3(+/+)) mice exhibited sensitized behavior and a significant increase in D(2)L and D(2)S mRNA compared with saline-pretreated mice Amphetamine-pretreated homozygous Ca(v)1.3 knockout (Ca(v)1.3(-/-)) mice did not exhibit sensitized behavior. There was a significant increase in D(2)S mRNA, but not D(2)L mRNA. In conclusion, our results find that amphetamine increases D(2)L mRNA expression in the dStr and the VTA, an adaptation that correlates with expression of sensitized behavior and dependence on Ca(v)1.3 Ca(2+) channels.

Neurotrophin-3 modulates noradrenergic neuron function and opiate withdrawal.

Somatic symptoms and aversion of opiate withdrawal, regulated by noradrenergic signaling, were attenuated in mice with a CNS-wide conditional ablation of neurotrophin-3. This occurred in conjunction with altered cAMP-mediated excitation and reduced upregulation of tyrosine hydroxylase in A6 (locus coeruleus) without loss of neurons. Transgene-derived NT-3 expressed by noradrenergic neurons of conditional mutants restored opiate withdrawal symptoms. Endogenous NT-3 expression, strikingly absent in noradrenergic neurons of postnatal and adult brain, is present in afferent sources of the dorsal medulla and is upregulated after chronic morphine exposure in noradrenergic projection areas of the ventral forebrain. NT-3 expressed by non-catecholaminergic neurons may modulate opiate withdrawal and noradrenergic signalling.

Regional sensitivity and coupling of BOLD and CBV changes during stimulation of rat brain.

Functional MRI of rat brain was performed at 2 Tesla following intravenous injection of cocaine in order to 1) determine if changes in CBV and changes in BOLD signal were regionally coupled in brain parenchyma, and 2) compare the sensitivities of these imaging methods across different brain structures. Percent changes in CBV and BOLD relaxation rate were spatially and temporally coupled during this graded brain activation. The use of contrast agent increased functional sensitivity in all parenchymal brain structures, with a strong but predictable dependence on the resting-state blood volume fraction. Magn Reson Med 45:443-447, 2001.

The effect of prenatal cocaine exposure on the stress response of adult mice.

The neurotoxic consequences of intrauterine exposure to drugs of abuse, including cocaine, may include compromised fetal brain development with associated lasting behavioral alterations. Some infants exposed to cocaine in utero demonstrate impairments in reactivity and altered behavioral responses to stressful conditions. Alterations in arousal regulation can impact on socialization, adaptation, and educability. Moreover, such alterations may render cocaine-exposed children more vulnerable to the adverse developmental impact of stressful situations, with implications for subsequent behavior and psychopathology. Animal models facilitate the independent analysis and identification of genetic, intrauterine, and postnatal environmental factors in contributing to cocaine-induced alterations in behavioral and neurochemical responses to stressors. Utilizing a prenatal mouse model of gestational cocaine exposure we have identified a behavioral alteration evident as decreased duration of footshock-induced immobility termed "freezing" in cocaine-exposed adults as compared with controls. However, this attenuated behavioral response was not accompanied by demonstrable alterations in corticosterone response, nor was the corticosterone response altered in cocaine-exposed adults following a more protracted restraint-induced stress. The dissociation of these behavioral and neurochemical indices of altered response to stressors may provide insights regarding brain mechanisms underlying alterations in behavioral reactivity to stressful conditions following in utero cocaine exposure. In addition, this preclinical study may have implications for improved diagnostics and therapeutics for infants and children exposed to cocaine in the womb.

Developmental considerations of neurotoxic exposures.

In this article, the authors provide a conceptual framework in which to consider alternative approaches to identify the developmental consequences of exposing the developing brain to neurotoxic substances. Concepts underlying brain development and issues regarding neurobehavioral testing in children are reviewed. In addition, the authors selectively review preclinical data identifying mechanisms contributing to neurobehavioral compromise, and clinical data identifying deficits resulting from exposure to two classes of neurotoxins: exposure to drugs of abuse, including alcohol, nicotine, and cocaine; and exposure to environmental agents, including lead, methyl-mercury, PCBs, and organophosphorus compounds.

Cocaine activation discriminates dopaminergic projections by temporal response: an fMRI study in Rat.

We applied a sensitive new functional magnetic resonance imaging technique to identify the pattern and determinants of cocaine-induced brain activation in drug-naive rats. At doses greater than 0.1 mg/kg iv, cocaine produced robust activation throughout cortex with the largest magnitude increase in frontal neocortex. Additionally, we detected selective activation within dopamine-innervated subcortical regions including dorsomedial and ventrolateral striatum, nucleus accumbens region, and dorsal thalamus. Although dose response was similar among activated regions, temporal response differentiated regions along distinct anatomical boundaries with basal ganglia and limbic cortical structures, reaching maximum activation later than frontal neocortex. Pharmacological specificity was demonstrated by blocking cocaine-induced activation with SCH-23390, a selective D1 antagonist. Our data demonstrate the utility of fMRI to identify spatiotemporal patterns of cocaine-induced brain activation and implicate D1 dopaminergic mechanisms in acute cocaine action.

Mechanisms of action of drugs of abuse on the developing fetal brain.

The consequences of public health of the acquisition and use of drugs of abuse have been well demonstrated. Despite intense effort, however, progress has been slow in recent years in ascertaining the specific neurodevelopmental effects of these drugs on the children of drug-abusing mothers. The use of animal models allows the investigator to determine the specific biological contributions of prenatal exposure to drugs of abuse on neurodevelopmental outcome while controlling for covariates that have confounded clinical studies, such as altered nutrition in pregnancy, suboptimal rearing environment of the young, and availability of drug and nondrug stimulation to the offspring. This article selectively reviews the preclinical literature on the gestational effects of drugs of abuse with particular emphasis on cocaine, ethanol, and the opiate narcotics. Mechanisms of drug action on the mature and developing brain are summarized. A model of developmental impact on the brain regions underlying drug-induced reward and reinforcement and its potential postnatal importance is presented.

A mouse model of transplacental cocaine exposure. Clinical implications for exposed infants and children.

To characterize the effects of cocaine on developing brain we have developed a mouse model of gestational cocaine exposure. We studied pregnant dams injected twice daily with cocaine HCl at 40, 20, or 10 mg/kg/day sc from embryonic days (E)8 to E17 (COC 40, COC20, and COC10, respectively), vehicle-injected dams allowed access to food ad libitum (SAL) or pair-fed with the COC 40 dams (SPF 40), animals pretreated with the short-acting alpha-adrenergic antagonist phentolamine prior to each cocaine injection (P COC 40), and animals administered phentolamine prior to saline (PHENT). COC 40, P COC 40, and SPF 40 dams demonstrated the lowest percentage weight gain during gestation. The surrogate-fostered offspring of COC 40, P COC 40, and SPF 40 dams demonstrated transient brain and body growth retardation on postnatal days (P)1 and P9 when compared to pups born to SAL dams. We conducted behavioral tests which allowed us to dissociate the indirect effect of cocaine-induced malnutrition from a direct effect of prenatal cocaine administration in altering postnatal behavior. Pups from all groups were tested for first-order Pavlovian conditioning on P9 or P12 or for the ability to ignore redundant information in a blocking paradigm on P50. Unlike the SPF 40, PHENT, and SAL controls, COC 40 and P COC 40 mice were unable to acquire an aversion to an odor previously paired with shock on P9, a learning deficit that resolved by P12. However, on P50, COC 40 mice and, to a lesser extent, P COC 40 and SPF 40 mice demonstrated a persistent behavioral deficit in our blocking paradigm, which may reflect alterations in selective attention. We discuss how these findings in our rodent model have developmental implications for human infants exposed to cocaine in utero.

Cocaine-induced alterations in neuro-development.

Gestational exposure to licit drugs of abuse such as alcohol and cigarettes, and illicit drugs of abuse such as marijuana, cocaine, and opiates is the single largest, preventable cause of in utero developmental compromise of infants in the United States today. Clinical and preclinical data suggest that cocaine may act as a behavioral teratogen, a drug capable of altering fetal brain development and subsequent function. Although many children exposed to cocaine in utero have normal development, some subset of infants, especially those who have sustained more significant prenatal exposures, are at risk for developmental compromise. There does not appear to be one outcome, but a spectrum of outcomes, which may relate to individual genetic differences in mothers and infants, to the specifics of the pregnant woman's cocaine habit, as well as to the richness of the postnatal environment. Alterations of arousal and habituation are evident in some cocaine-exposed neonates, especially following greater in utero exposures. Subtle but profoundly important behavioral deficits may persist, as recent data suggests that some cocaine-exposed children may have particular difficulty modulating attention, impulsivity, and responsivity, which are critically challenged in classroom settings. The goals of this article are to present concepts required to better understand cocaine-induced alterations in neuro-development, to outline mechanisms that may underlie such changes, and to discuss the potential clinical consequences of such alterations.

Transplacental cocaine exposure. 2: Effects of cocaine dose and gestational timing.

We have utilized a mouse model of transplacental cocaine exposure to investigate the effects of cocaine dose and gestational timing in altering brain and body growth and postnatal behavior in exposed offspring. Pregnant dams were injected with cocaine HCl at 40 mg/kg/day (COC 40) or 20 mg/kg/day (COC 20), or 10 mg/kg/day (COC 10) SC from embryonic day (E) 8 to E17, or cocaine HCl at 40 mg/kg/day SC from E8 to E13 (COC Early) or from E13 to E17 (COC Late) divided in two daily doses. COC 40 and COC Late dams, as well as dams in nutritionally paired control groups (injected with saline vehicle and pair-fed with the COC dams: SPF 40, SPF 20, SPF 10), demonstrated less weight gain than SAL controls (injected with saline vehicle and allowed access to food ad lib). The surrogate fostered offspring of COC 40 and SPF 40 dams demonstrated brain and body growth retardation [on postnatal day (P) 1 and P9] when compared to pups born to SAL dams. Offspring of COC Late, SPF 20, and SPF 10 dams demonstrated brain and body growth retardation on P1 when compared to pups born to SAL dams. Pups from all groups were tested for first-order Pavlovian conditioning on P9, or for the ability to ignore redundant information in a blocking paradigm on P50. Only COC 40 mice (i.e., offspring born to COC 40 dams) were unable to acquire an aversion to an odor previously paired with shock on P9. When compared with SAL controls, COC 40 mice (and to a less significant extent SPF 40 mice) demonstrated a persistent behavioral deficit in the blocking paradigm on P50, which may reflect alterations in selective attention. Correlation analyses indicated that the dose and gestational timing of transplacental cocaine exposure, and varying degrees of malnutrition, had effects on blocking performance, with greater prenatal cocaine exposure and increased prenatal malnutrition resulting in more significant behavioral impairments. A path regression analysis demonstrated independent and significant effects of prenatal cocaine as well as prenatal malnutrition in contributing to impaired performance in the blocking paradigm. As suggested by the clinical literature, our preclinical data support a model whereby the dose and duration of prenatal cocaine exposure have direct effects on offspring brain and body growth and on behavioral performance.

Transplacental cocaine exposure. 1: A rodent model.

To characterize the transplacental effects of cocaine on the developing brain, we have developed a mouse model of gestational cocaine exposure. Pharmacokinetic analysis revealed that cocaine and its metabolites (BE, BNE, and NC) were found in fetal brain and plasma at 30 and 120 min following SC administration to embryonic day (E) 17 pregnant Swiss Webster mice. Pregnant dams injected twice daily with cocaine HCl at 20 mg/kg SC from gestational day E8 to E17 (COC) demonstrated less food intake and lower percentage weight gain than vehicle-injected dams allowed access to food ad lib (SAL). A nutritionally paired control group of dams injected with saline vehicle and pair-fed with the COC dams (SPF) demonstrated the lowest percentage weight gain of all three groups. The surrogate fostered offspring of COC and SPF dams demonstrated persistent growth retardation [on postnatal days (P) 1, P9, and P50] and transient brain growth retardation (on P1 and P9) when compared to pups born to SAL dams. We conducted behavioral tests that allowed us to dissociate the indirect effect of cocaine-induced malnutrition from a direct effect of prenatal cocaine administration in altering postnatal behavior. Pups from all three groups were tested for first-order Pavlovian conditioning on P9 or P12, or for the ability to ignore redundant information in a blocking paradigm on P50 or P100. Unlike the SPF and SAL controls, COC mice (i.e., mice born to COC dams) were unable to acquire an aversion to an odor previously paired with shock on P9. This learning deficit was transient because on P12, COC mice trained on the same conditioning task displayed an aversion to the odor that was indistinguishable from the SPF and SAL controls. P50 and P100 COC mice (and to a lesser extent, SPF mice) demonstrated a persistent behavioral deficit in the blocking paradigm, which may reflect alterations in selective attention. We discuss how these findings in our rodent model have developmental implications for human infants exposed to cocaine in utero.

Transplacental cocaine exposure. 3: Mechanisms underlying altered brain development.

In a mouse model of transplacental cocaine exposure we have demonstrated alterations in brain structure and function of offspring including disturbances of brain growth, disruption of neocortical cytoarchitecture, and transient as well as persistent behavioral deficits. One mechanism by which cocaine may alter fetal brain development is through cocaine-induced alpha-adrenergic-mediated (uterine) arterial vasoconstriction. In this study pregnant Swiss Webster (SW) mice were injected with cocaine HCl (20 or 40 mg/kg, SC) without any changes evident in mean arterial blood pressure (MAP) measurements. These physiology results suggest that in our mouse model, cocaine's transplacental effects on the fetus are not due to cocaine-induced maternal vasoconstriction, nor concomitant hypoperfusion of the fetus. In a separate series of experiments, pregnant SW dams were administered cocaine HCl at 40 mg/kg/day (COC 40), 20 mg/kg/day (COC 20), or 10 mg/kg/day (COC 10) [SC, divided in two daily doses, from embryonic day (E) 8 to E17 inclusive]. Additional groups of cocaine-treated dams were administered phentolamine (5 mg/kg, SC), a short-acting alpha-adrenergic antagonist, 15 min prior to each cocaine dose (Phent COC 40, Phent COC 20, Phent COC 10). Animals born to Phent COC 40 dams demonstrated transient postnatal brain growth retardation and behavioral deficits in first-order conditioning of P9 mice comparable to mice born to COC 40 dams, which received the same regimen of cocaine injections without phentolamine pretreatment. Like COC 40 offspring, Phent COC 40 offspring also demonstrated a persistent deficit in the blocking paradigm. The behavioral and growth findings confirm and extend the physiology data, and imply that in our rodent model, alpha-adrenergic mechanisms (including maternal vasoconstriction) are unlikely to mediate these toxic effects of transplacental cocaine exposure on developing brain.

Dynamic functional imaging of relative cerebral blood volume during rat forepaw stimulation.

Dynamic measurements of regional changes in cerebral blood volume (CBV) were performed in rat models of hypercarbia and focal neuronal activation using T2-weighted imaging after injection of an intravascular contrast agent with a very long blood half-life. Calculated percent CBV change during hypercarbia was consistent with literature results from other non-invasive modalities. Equivalent percent CBV increases were found using spin- and gradient-echo images, suggesting proportional changes in blood volume for capillaries and small veins. During electrical stimulation of rat forepaw, focal CBV response to stimulation (24+/-4%) was significantly delayed relative to blood oxygen level dependent (BOLD) signal after both onset and cessation of stimulation. Poststimulus CBV decay was temporally consistent with the BOLD poststimulus undershoot. The use of exogenous agent increased the functional contrast-to-noise ratio relative to BOLD imaging by 5.7+/-1.3 at a magnetic field strength of 2 Tesla and 1.5+/-0.2 at 4.7 Tesla.

Acute hydrocephalus following carbon monoxide poisoning.

Carbon monoxide remains a significant cause of poisoning in children. Cerebral edema is often the cause of significant morbidity and mortality in exposed children. While lesions of the basal ganglia have been well documented, the advent of neuroimaging has allowed antemortem demonstration of infarctions of the globus pallidus and putamen with carbon monoxide intoxication. Acute hydrocephalus following carbon monoxide poisoning has been a rare occurrence. We report a 2 year 6 month-old boy who, to our knowledge, represents the first reported case in which repeat computed tomography documented the evolution of hydrocephalus due to carbon monoxide exposure in a child.

Cellular localization of dopamine D2 receptor messenger RNA in the rat trigeminal ganglion.

The actions of dopamine are mediated by specific, high-affinity, G protein-coupled receptors. Multiple subtypes of dopamine receptors have been characterized, including the D2 subtype (D2R). Cells within the dorsal root and petrosal ganglia of the rat express D2R messenger RNA (mRNA) consistent with D2R expression by primary sensory neurons. We hypothesized that neurons of the trigeminal ganglion express D2R mRNA. Total cellular RNA from rat trigeminal ganglia was analyzed on Northern blots under high stringency conditions. Hybridization of trigeminal ganglion RNA resulted in a signal which comigrated with striatal, pituitary, and hypothalamic D2R mRNA. To determine the distribution of D2R expressing cells in the trigeminal ganglion, cryostat sections were analyzed by in situ hybridization followed by emulsion autoradiography. We identified a population of clustered cells labeled with dense grain concentrations over their cytoplasms. These findings demonstrate the expression of D2 dopamine receptor mRNA in discrete subpopulations of neurons in the rat trigeminal ganglion. Our observations suggest that drugs active at dopamine receptors of the D2 subtype are potential modulators of sensory activity of neurons whose cell bodies reside in the trigeminal ganglion. D2 dopamine receptors may thus have a role in clinical pain syndromes involving the head and neck.

Refined localization of the cerebral cavernous malformation gene (CCM1) to a 4-cM interval of chromosome 7q contained in a well-defined YAC contig.

Cerebral cavernous malformations (CCM) are vascular lesions present in some 20 million people worldwide that are responsible for seizures, migraine, hemorrhage, and other neurologic problems. Familial cases ofCCM can be inherited as an autosomal dominant disorder with variable expression. A gene for CCM (CCM/)was recently mapped to a 33-cM segment of chromosome 7q in a large Hispanic family (Dubovsky et al.1995). Here, the collection of several new short tandem repeat polymorphisms (STRPs) within the region of interest on 7q and the refinement of the marker order in this region using both linkage analysis in CEPH families and especially YAC-based STS content mapping are described. Affected members of three Hispanic families share allele haplotypes indicating a common ancestral mutation within these families. Using the shared haplotype information along with analysis of crossovers in affected individuals from both the Hispanic and Caucasian families, the region likely to contain the CCMI gene has been reduced to a 4-cM segment of 7q between D7S2410 and D7S689. All markers within the refined chromosomal segment were located on a single YAC contig estimated to be approximately 2 Mb in size. Four potential candidate genes have been mapped to this region.