RESUMEN
Stimulants are an effective treatment frequently prescribed for attention-deficit-hyperactivity disorder (ADHD), but they commonly are believed to lower the threshold for seizures. Although several studies have revealed that stimulants do not exacerbate well-controlled epilepsy, there is a paucity of data about seizure risk in nonepileptic children treated with stimulants. Two hundred thirty-four children (179 males, 9.1 +/- 3.6 years of age; 55 females, 9.6 +/- 3.9 years of age) with uncomplicated ADHD received electroencephalograms (EEGs) performed in our institution. Thirty-six patients (15.4%) demonstrated epileptiform abnormalities, and 198 (84.6%) demonstrated normal or nonepileptiform EEGs. Rolandic spikes accounted for 40% of the abnormal EEGs and 60% of those with focal abnormalities. Stimulant therapy was elected by 205 of 234 patients (87.6%). Seizures occurred only in the treated group, in one of 175 patients with a normal EEG (incidence 0.6%, 95% confidence intervals 0%-1.7%) and three of 30 treated patients with epileptiform EEGs (incidence 10%, 95% confidence interval 0%-20.7%). Seizures occurred in two of 12 children (16.7%) with rolandic spikes. These data suggest that a normal EEG can be used to assign children with ADHD to a category of minimal risk for seizure. In contrast, an epileptiform EEG in neurologically normal children with ADHD predicts considerable risk for the eventual occurrence of seizure. The risk, however, is not necessarily attributable to stimulant use.
Asunto(s)
Trastorno por Déficit de Atención con Hiperactividad/tratamiento farmacológico , Encéfalo/fisiopatología , Estimulantes del Sistema Nervioso Central/efectos adversos , Electroencefalografía , Convulsiones/inducido químicamente , Adolescente , Adulto , Anfetaminas/efectos adversos , Anticonvulsivantes/administración & dosificación , Trastorno por Déficit de Atención con Hiperactividad/complicaciones , Trastorno por Déficit de Atención con Hiperactividad/fisiopatología , Estimulantes del Sistema Nervioso Central/administración & dosificación , Niño , Preescolar , Quimioterapia Combinada , Femenino , Humanos , Masculino , Registros Médicos , Metilfenidato/efectos adversos , Pronóstico , Estudios Retrospectivos , Convulsiones/etiología , Convulsiones/fisiopatología , Resultado del TratamientoRESUMEN
We studied the development of glutamatergic neurotransmission in dentate gyrus granule cells (GCs) in hippocampal slices from 5 to 12-day-old rats. The active postnatal neuronogenesis in dentate permits GCs with staggered birthdates to be studied in situ in a single preparation. We recorded evoked responses to medial perforant path stimulation using visually-guided whole-cell patch clamping to select immature GCs, and biocytin filling to correlate electrophysiologic responses with maturational stage. Even within this immature cell population we found four distinct electrophysiologic patterns. Type 1 cells had no glutamatergic current; Type 2 cells had only N-methyl-D-aspartate receptor (NMDA) current; Type 3 cells had both NMDA and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) current although the NMDA component could be isolated at low stimulus intensity (NMDA threshold
Asunto(s)
Giro Dentado/fisiología , Ácido Glutámico/fisiología , Neuronas/fisiología , Transmisión Sináptica/fisiología , Animales , Animales Recién Nacidos/crecimiento & desarrollo , Animales Recién Nacidos/fisiología , Senescencia Celular/fisiología , Giro Dentado/citología , Giro Dentado/crecimiento & desarrollo , Giro Dentado/ultraestructura , Potenciales Evocados/fisiología , Femenino , Técnicas In Vitro , Masculino , Ratas , Ratas Sprague-Dawley , Receptores AMPA/fisiología , Receptores de N-Metil-D-Aspartato/fisiologíaRESUMEN
Dentate gyrus granule cells from immature (7-28 days) Sprague-Dawley rats were examined with whole cell patch clamp recordings and biocytin filling in in vitro hippocampal slice preparations. Although recordings were confined to the middle third of the suprapyramidal limb of the dentate, the granule cells exhibited marked variability in their physiologic properties: input resistance (IR) ranged from 250 MOmega to 3 GOmega, and resting membrane potential (RMP) from -82 to -41 mV. Both IR and RMP were inversely correlated with dendritic length, a morphometric indicator of cell maturity. Thus the highest IR cells were the youngest, and maturation was characterized by a progressive decrease in IR, hyperpolarization of RMP, and elongation of the dendritic arbor. When cells were grouped by IR, significant intergroup differences were found in RMP, dendritic length, and number of dendritic terminal branches. Although cells of all IR categories were examined throughout the age spectrum under study, none of the inter-IR group differences was age-dependent. These data suggest that IR provides a reasonable estimate of granule cell maturity and that maturation entails predictable changes in cell properties and morphology. These aspects of maturation correlate with each other, are independent of animal age, and most likely proceed according to a program related to cell birth.
Asunto(s)
Envejecimiento/fisiología , Giro Dentado/fisiología , Neuronas/fisiología , Animales , Dendritas/fisiología , Dendritas/ultraestructura , Giro Dentado/citología , Giro Dentado/crecimiento & desarrollo , Femenino , Técnicas In Vitro , Masculino , Potenciales de la Membrana/fisiología , Neuronas/citología , Técnicas de Placa-Clamp , Ratas , Ratas Sprague-Dawley , Análisis de RegresiónRESUMEN
Joubert's syndrome is an autosomal-recessive condition characterized by dysgenesis of the cerebellar vermis, hypotonia, developmental delay, a respiratory pattern of alternating tachypnea and apnea, and abnormal eye movements. Radiologic findings include a midline cerebellar cleft in place of the vermis and a characteristic shape of the fourth ventricle. Prenatal hydrocephalus has been proposed as a possible etiology for the cerebellar abnormalities but has not previously been described in association with this syndrome. The authors report a patient with clinical and radiographic features consistent with Joubert's syndrome who presented with congenital hydrocephalus.
Asunto(s)
Anomalías Múltiples/diagnóstico , Encéfalo/anomalías , Hidrocefalia , Diagnóstico Prenatal , Encéfalo/patología , Femenino , Humanos , Hidrocefalia/complicaciones , Hidrocefalia/diagnóstico , Recién Nacido , SíndromeRESUMEN
We used whole cell patch clamp and gramicidin perforated patch recordings in hippocampal slices to study gamma-aminobutyric acid (GABA) currents in granule cells (GCs) from juvenile rat dentate gyrus (DG). GCs are generated postnatally and asynchronously such that they can be detected at different stages of their maturation in DG within the first month. In contrast, inhibitory interneurons are generated embryonically, and their circuitry is well developed even as their target GCs and GC excitatory connections are still being formed. In this study, two GABA currents evoked in GCs by medial perforant path stimulation are compared. The first, pharmacologically isolated by glutamate receptor blockade, is the product of direct activation of GABA interneurons with monosynaptic input to the recorded GC (monosynaptic GABAA). Monosynaptic GABAA displays slight outward rectification of its current-voltage relation, is 97% eliminated by 10 microM bicuculline and coincides temporally with the excitatory components of GC postsynaptic currents as has been described for GABAA currents in other brain regions. The second is a novel GABA response that is detectable in 10 microM bicuculline and is present on GCs only at the earliest stages of their maturation. Unlike monosynaptic GABAA, this transient GABA is eliminated by glutamate receptor blockade and hence is likely to be generated by interneurons activated via an intervening glutamatergic synapse (polysynaptically). It is predominantly chloride mediated, has a relative bicarbonate/chloride permeability ratio of 26%, and is unchanged by bath-applied saclofen and strychnine or by intracellular calcium chelation. It is 97% antagonized by 100 microM picrotoxin and 99% antagonized by 100 microM bicuculline. This current is thus a relatively bicuculline (BMI)-resistant GABAA current (BMIR-GABAA). Compared with monosynaptic GABAA, BMIR-GABAA has a later peak, slower time course of decay, and marked outward rectification. Its reversal potential is 7-8 mV depolarized to that of monosynaptic GABAA whether recorded in whole cell or with gramicidin perforated patch to preserve native internal chloride concentration. Together these data may suggest that BMIR-GABAA is evoked by an anatomically segregated population of interneurons activating a unique, developmentally regulated GABAA receptor. Further, the transient nature of this current coupled with its temporal characteristics that preclude overlap with the excitatory components of the synaptic response are consistent with a role that is trophic or signaling rather than primarily inhibitory.
Asunto(s)
Giro Dentado/fisiología , Interneuronas/fisiología , Receptores de GABA-A/fisiología , Animales , Bicuculina/farmacología , Giro Dentado/citología , Giro Dentado/efectos de los fármacos , Giro Dentado/crecimiento & desarrollo , Conductividad Eléctrica , Potenciales Evocados/efectos de los fármacos , Potenciales Evocados/fisiología , Antagonistas de Aminoácidos Excitadores/farmacología , Femenino , Antagonistas del GABA/farmacología , Técnicas In Vitro , Interneuronas/efectos de los fármacos , Masculino , Técnicas de Placa-Clamp , Ratas , Ratas Sprague-Dawley , Receptores de GABA-A/efectos de los fármacos , Sinapsis/efectos de los fármacos , Sinapsis/fisiología , Ácido gamma-Aminobutírico/farmacologíaRESUMEN
The effects of bath application of the metabotropic glutamate receptor (mGluR) agonist 1S,3R-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD, 10 microM) were studied at the Schaffer collateral-CA1 synapse in hippocampal slices from rats of 8-33 days postnatal age. In immature animals (8-12 days) ACPD induced a biphasic response characterized by an acute decrease in field EPSP slope (approximately 50-60% of baseline) in the presence of the agonist, followed by long-term depression (LTD, approximately 75-80% of baseline) after washout. In animals older than 20 days, ACPD induced a slow onset potentiation or minimal change. Both the acute depression and LTD were blocked by the mGluR antagonist alpha-methyl-4-carboxyphenyl glycine (MCPG). ACPD-induced LTD was blocked by the N-methyl-D-aspartate receptor (NMDAR) antagonists D(-)-2-amino-5 phosphopentanoic acid (AP5) and dizocilpine maleate (MK-801), and by ethanol. Glutamic pyruvic transaminase, an enzyme that selectively metabolizes endogenous extracellular glutamate, also blocked LTD suggesting that the requisite NMDA currents were tonically activated by extracellular rather than synaptically released glutamate. ACPD-induced LTD was blocked by staurosporine, indicating a requirement for serinethreonine kinase activation, and was unaffected by the L-type voltage sensitive calcium channel blocker nitrendipine and the A1 adenosine receptor antagonist 8-cyclopentyl-1,3-dimethylxanthine (CPT). Because mGluR-mediated LTD was observed only in immature CA1, mGluRs may play a role in hippocampal development, perhaps by contributing to synapse pruning in a temporally restricted fashion.
Asunto(s)
Hipocampo/efectos de los fármacos , Receptores de Glutamato Metabotrópico/fisiología , Transmisión Sináptica/efectos de los fármacos , Animales , Benzoatos/farmacología , Cicloleucina/análogos & derivados , Cicloleucina/farmacología , Depresión Química , Estimulación Eléctrica , Potenciales Evocados/efectos de los fármacos , Antagonistas de Aminoácidos Excitadores/farmacología , Glicina/análogos & derivados , Glicina/farmacología , Hipocampo/crecimiento & desarrollo , Hipocampo/fisiología , Técnicas In Vitro , Plasticidad Neuronal/efectos de los fármacos , Fármacos Neuroprotectores/farmacología , Nitrendipino/farmacología , Ratas , Ratas Sprague-Dawley , Receptores de Glutamato Metabotrópico/efectos de los fármacos , Transmisión Sináptica/fisiología , Teofilina/análogos & derivados , Teofilina/farmacologíaRESUMEN
Although reductions in neurotransmission have been reported in response to agonist-mediated adenosine A1 receptor activation, the implications of A2 receptor activation on synaptic transmission have not been well explored. We examined the role adenosine A2 receptors play in the efficacy of neurotransmission between the Schaffer collateral-CA1 pathway in the rat transverse hippocampal slice. A2 receptor blockade in the presence of complete A1 receptor inhibition led to a reversible reduction of the field excitatory post-synaptic potential (EPSP) slope in response to low-frequency test pulses (0.033 Hz) indicating that A2 receptors can enhance synaptic transmission. A2 receptor blockade by the A2 antagonist, DMPX (3,7-dimethyl-1-propargylxanthine) prevented the induction of tetanus-induced long-term potentiation (LTP) of the EPSP. In contrast, no such effect on LTP induction was observed during A1 receptor blockade. We also examined the effects of DMPX on the induction of LTP during continued A1 receptor blockade with CPT. Under this condition, LTP was significantly reduced when compared to LTP induced in the presence of CPT alone. A similar result was found using the highly polar A2 antagonist 8-SPT (8-(p-sulfophenyl)theophylline) suggesting that the effects of DMPX on LTP were not due to a direct action on an intracellular intermediate. DMPX had no effect on LTP expression if applied 45 min following the tetanus indicating that A2 receptors play no significant role in the maintenance phase of LTP. Selective A2a receptor activation did not alter the field EPSP. Similarly, selective blockade of the A2a receptor did not interfere with tetanus-induced LTP. Increases in neuronal firing rates can result in elevations in the concentration of extracellular adenosine. Together, these results suggest that the A2 receptors may play an important role in the induction although not the maintenance of hippocampal LTP and that the effect is likely to be mediated by the A2b receptor.
Asunto(s)
Hipocampo/metabolismo , Potenciación a Largo Plazo , Receptores Purinérgicos P1/fisiología , Adenosina/análogos & derivados , Adenosina/farmacología , Animales , Hipocampo/fisiología , Potenciación a Largo Plazo/efectos de los fármacos , Fenetilaminas/farmacología , Agonistas del Receptor Purinérgico P1 , Antagonistas de Receptores Purinérgicos P1 , Ratas , Ratas Sprague-Dawley , Transmisión Sináptica/fisiología , Teobromina/análogos & derivados , Teobromina/farmacología , Teofilina/análogos & derivados , Teofilina/farmacologíaRESUMEN
Long-term depression (LTD) is a decrease in synaptic efficacy that may model the elimination of inappropriate synapses during brain development. LTD might therefore be expected to be prominent in the juvenile hippocampal dentate gyrus (DG), where the majority of neuronogenesis and excitatory synapse production and pruning occur in the first postnatal month. Thus far, however, LTD in immature DG remains unexplored. Low-frequency stimulus induced homosynaptic LTD was studied at the medial perforant path-granule cell synapse in rats 8-30 days of age. LTD was most consistent and was of greatest magnitude in the youngest animals, and was more robust in response to stimulation at 1 Hz than at 3 or 5 Hz. LTD was saturable by repetitive delivery of low-frequency stimulation, and reversible by tetanic stimulation that induced long-term potentiation (LTP). LTD of the field EPSP was not prevented by bath application of the NMDA receptor antagonist AP5, the mGluR antagonist MCPG, or the L-type voltage sensitive calcium channel antagonist nitrendipine. In whole cell recordings LTD induction was blocked by hyperpolarization of the postsynaptic neuron but not by calcium chelation with BAPTA. Calcium chelation blocked LTP and simultaneously unmasked tetanus induced LTD. These data demonstrate that LTD is prominent in immature DG, that LTP and LTD are complementary processes, and that LTD is likely to be induced postsynaptically because it is voltage dependent, although the mechanism of voltage dependence remains to be elucidated.
Asunto(s)
Giro Dentado/fisiología , Plasticidad Neuronal/fisiología , Neuronas/fisiología , Sinapsis/fisiología , 2-Amino-5-fosfonovalerato/farmacología , Animales , Benzoatos/farmacología , Bloqueadores de los Canales de Calcio/farmacología , Giro Dentado/efectos de los fármacos , Giro Dentado/crecimiento & desarrollo , Estimulación Eléctrica , Potenciales Evocados/efectos de los fármacos , Antagonistas de Aminoácidos Excitadores/farmacología , Femenino , Glicina/análogos & derivados , Glicina/farmacología , Técnicas In Vitro , Masculino , Plasticidad Neuronal/efectos de los fármacos , Neuronas/efectos de los fármacos , Técnicas de Placa-Clamp , Ratas , Ratas Sprague-Dawley , Receptores de Glutamato Metabotrópico/antagonistas & inhibidores , Receptores de N-Metil-D-Aspartato/antagonistas & inhibidores , Sinapsis/efectos de los fármacosRESUMEN
1. Whole cell patch-clamp recordings were used to study dentate gyrus granule cells in hippocampal slices from juvenile rats (postnatal days 8-32). Membrane properties were measured with the use of current-clamp recordings and were correlated with the morphology of a subgroup of neurons filled with biocytin. The components of the postsynaptic currents (PSCs) induced by medial perforant path stimulation were characterized with the use of specific receptor antagonists in voltage-clamp recordings. 2. Granule cells located in the middle third of the superior blade of stratum granulosum from the rostral third of hippocampus were divided into three groups according to their input resistance (IR). Neurons with low IR (206 +/- 182 M omega, mean +/- SD) had hyperpolarized resting membrane potentials (-82 +/- 7 mV) and high-amplitude action potentials (108 +/- 23 mV). Neurons were high IR (1,259 +/- 204 M omega) had more depolarized resting membrane potentials (-54 +/- 6 mV) and lower-amplitude action potentials (71 +/- 10 mV). Neurons with intermediate IR (619 +/- 166 M omega) also had intermediate resting membrane potentials (-63 +/- 7 mV) and action potential amplitudes (86 +/- 14 mV). Low-IR neurons became increasingly prevalent with advancing postnatal age, but neurons from each group could be found throughout the entire period under study. 3. Morphological studies of low-IR neurons revealed an extensive dendritic arborization that traversed the entire molecular layer and was characteristic of mature granule cells. High-IR cells had smaller somata and short, simple dendritic arborization that incompletely penetrated the molecular layer and were classified as immature. Intermediate-IR cells had morphological features of intermediate maturity. 4. The initial phase of the PSC evoked at -80 mV was a fast inward current that was comparable with respect to latency to peak, latency to onset, and 10-90% rise time in neurons of all maturities held at -80 mV. This current was 6-cyano-7-nitroquinoxaline-2,3-dione sensitive. 5. The decay phases of PSCs at -80 mV varied with neuronal maturity. Mature neurons had monoexponential decays (tau = 8.9 +/- 3.6). Intermediate and immature neurons had prominent later inward currents that resulted in slower decays. In the case of the immature neurons, the inward current during the decay phase could be separated from the initial fast inward peak. The later inward currents in intermediate and immature neurons were bicuculline sensitive. 6. With the use of uniform ionic conditions of the extracellular and patch solutions, current-voltage relations and reversal potentials for pharmacologically isolated alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), N-methyl-D-aspartate (NMDA), and gamma-aminobutyric acid-A (GABAA) currents were comparable across all cell maturities. Calculated ratios for peak GABAA/NMDA/AMPA currents decreased significantly with maturation as follows: 9.4 +/- 2.9/1.4 +/- 0.5/1.0 for immature cells, 7.2 +/- 2.5/1.5 +/- 0.7O/1.0 for intermediate cells, and 2.0 +/- 1.2/0.9 +/- 0.4/1.0 for mature cells. 7. GABA current was mediated both by polysynaptic activation of interneurons and by direct activation of interneurons with monosynaptic input onto granule cells. The proportional contributions of mono- and polysynaptic GABA to total GABA were comparable across all cell maturities; latency to peak GABA current decreased with increasing cell maturity for both mono- and polysynaptic components. 8. We conclude that PSCs evoked in granule cells by medial perforant path activation in neurons of all maturities consist of both glutamatergic and GABAergic components. PSCS are dominated by GABAergic neurotransmission in immature granule cells, and the contribution of glutamatergic neurotransmission increases with neuronal maturation. The greater ratio of peak GABAA to glutamate currents and the longer time interval between their respective peaks combine to produce a distinctive PSC shape
Asunto(s)
Giro Dentado/fisiología , Sinapsis/fisiología , Animales , Animales Recién Nacidos , Membrana Celular/fisiología , Giro Dentado/crecimiento & desarrollo , Giro Dentado/ultraestructura , Potenciales Postsinápticos Excitadores/fisiología , Femenino , Ácido Glutámico/fisiología , Técnicas In Vitro , Masculino , Potenciales de la Membrana/fisiología , Ratas , Ratas Sprague-Dawley , Tiempo de Reacción , Receptores de GABA-A/fisiología , Sinapsis/metabolismo , Ácido gamma-Aminobutírico/fisiologíaRESUMEN
The primary goal of this retrospective study was to assess parental report of current sleep disorders in school-aged attention deficit disorder (ADD) children, as well as recalled sleep problems from when the children were infants (0-12 months) and toddlers (1-3 years). Results of a sleep questionnaire completed by mothers of 48 ADD children and a comparison group of 30 patients with school problems indicate that ADD children were perceived to have significantly more sleep problems and that these problems had onset in infancy. Specific items in the questionnaire which were increased included latency to sleep onset of more than 30 min at least 3 nights per week, fatigue upon awakening, and recall of nightmares. Pediatric clinicians should be alert to possible sleep disorders in children suspected of attention disorders and should consider "sleep hygiene" measures as a component of treatment.
RESUMEN
The hippocampal dentate gyrus undergoes active neuronogenesis as well as growth and regression of neuronal elements and connections during the early postnatal period. In some brain regions, most notably in the visual system, both activity-dependent synaptic plasticity and NMDA receptor activation are candidate mechanisms by which neuronal architecture may be refined during brain maturation. To investigate whether similar mechanisms might obtain in developing dentate, we studied the effects of tetanic stimulation before and after NMDA receptor blockade in hippocampal slices from rats at 7-33 days. Field potentials were recorded in the suprapyramidal granule cell layer in response to stimulation of the medial perforant path. Robust long-term potentiation (LTP) of population spike amplitude (approximately 200% of baseline) was produced by a single tetanus (100 Hz, 2 s, 200 microseconds) at all ages studied. Application of 10 microM AP5 depressed population spike amplitude only in the younger slices (approximately 81% of baseline at 8-15 days; approximately 86% of baseline at 16-24 days), suggesting that the NMDA receptor-mediated component of normal synaptic transmission is higher in early development and decreases with maturation. AP5 prevented or significantly diminished LTP at all ages, establishing the NMDA dependence of LTP induction in the medial perforant path throughout development. AP5 also unmasked tetanus-induced homosynaptic long-term depression (62-75% of baseline) in the younger slices (8-24 days). Thus, prominent NMDA receptor-mediated activity and the capacity for bidirectional synaptic plasticity are characteristic of immature dentate. These processes may influence dentate morphogenesis by contributing to the growth, regression, and stabilization of neuronal elements.
Asunto(s)
2-Amino-5-fosfonovalerato/farmacología , Hipocampo/fisiología , Potenciación a Largo Plazo/efectos de los fármacos , Potenciales de Acción/efectos de los fármacos , Animales , Animales Recién Nacidos , Femenino , Masculino , Plasticidad Neuronal , Ratas , Ratas Sprague-Dawley , Receptores de N-Metil-D-Aspartato/antagonistas & inhibidores , Receptores de N-Metil-D-Aspartato/fisiología , Sinapsis/fisiologíaRESUMEN
The effects of rapid perforant path kindling on field potentials and paired pulse depression were studied in the dentate gyrus of rats at four developmental stages: 14-16 days, 20-22 days, 27-29 days and 40-60 days (adult). In rats 14-29 days kindling was associated with sustained potentiation of population spike amplitude and population EPSP slope; in adults a progressive decline was seen in both measures. Inhibitory circuitry as assessed by paired pulse depression was intact at all ages studied. Kindling produced no lasting changes in this measure at 14-22 days; in the older age groups a significant increase in paired pulse depression was seen. Thus immature animals differed from adults in that they manifested persistent facilitation of excitatory transmission as a result of kindling and failed to mount a compensatory inhibitory response. These results suggest that the balance between excitation and inhibition is more readily shifted toward excitation in immature animals in a manner that may contribute to their unique vulnerability to epileptogenesis.
Asunto(s)
Hipocampo/fisiología , Excitación Neurológica/efectos de los fármacos , Envejecimiento/fisiología , Animales , Electrodos Implantados , Potenciales Evocados/efectos de los fármacos , Hipocampo/citología , Hipocampo/crecimiento & desarrollo , Potenciación a Largo Plazo/efectos de los fármacos , Ratas , Ratas Sprague-DawleyRESUMEN
The go-no go test requires a subject to emit a simple motor response to one cue while inhibiting the response in the presence of another cue. This test has been effective in demonstrating impulsivity (elevated commission error rate) in children with attention deficit disorder (ADD). In this study, we examined the effects on go-no go test performance of two doses of methylphenidate (0.15 mg/kg and 0.3 mg/kg) administered in double-blind placebo-controlled fashion to children with ADD. Our results indicate that even modest doses of methylphenidate improve the go-no go performance of these children by decreasing their tendency to make impulsive commission errors. Thus the test is sensitive to the effects of methylphenidate and can be used to monitor a response to therapy.
Asunto(s)
Trastorno por Déficit de Atención con Hiperactividad/diagnóstico , Metilfenidato , Adolescente , Análisis de Varianza , Trastorno por Déficit de Atención con Hiperactividad/tratamiento farmacológico , Niño , Método Doble Ciego , Femenino , Estudios de Seguimiento , Humanos , Masculino , Metilfenidato/uso terapéuticoRESUMEN
N-Methyl-D-aspartate (NMDA) receptor antagonists inhibit both the kindling process and the expression of seizures in previously kindled adult rats. Experimental seizures are more readily produced in infant than adult rats, possibly related to a developmental predominance of NMDA receptor-mediated effects. If so, reduction of seizure susceptibility by NMDA receptor antagonists should be more dramatic in infant rats than in adults. We studied the effect of ketamine and MK-801 on kindling epileptogenesis and seizure expression in 15-day-old rats. Ketamine (5, 10, and 20 mg/kg) and MK-801 (0.033 and 0.1 mg/kg) both significantly increased the latency to stage 3 or 4 seizures in dose-dependent fashion. These results were similar to those found in adults but occurred at slightly lower doses. Ketamine 20 mg/kg and MK-801 0.33 mg/kg totally eliminated clinical seizure activity and nearly abolished afterdischarge in previously kindled infant rats, effects exceeding those reported in adults using doses up to 6 times as great. These results support the hypotheses that NMDA receptor-mediated neurotransmission plays an important role in seizure production and the increased seizure susceptibility in immature brain and raise the possibility that NMDA receptor antagonists could be useful antiepilepsy agents in young children.
Asunto(s)
Dibenzocicloheptenos/farmacología , Ketamina/farmacología , Excitación Neurológica , Receptores de Neurotransmisores/fisiología , Convulsiones/metabolismo , Animales , Maleato de Dizocilpina , Ratas , Tiempo de Reacción/efectos de los fármacos , Receptores de N-Metil-D-Aspartato , Receptores de Neurotransmisores/antagonistas & inhibidores , Convulsiones/fisiopatologíaRESUMEN
In rats 14-28 days of age, high-frequency stimulation of the perforant path granule cell synapse in the dentate gyrus produced long-term potentiation of the population spike that was comparable in magnitude (150-250% of baseline) and duration (120 min) to that produced in adult animals with the same stimulation paradigm. In contrast, potentiation of the excitatory postsynaptic potential occurred inconsistently.
Asunto(s)
Adaptación Fisiológica , Envejecimiento/fisiología , Hipocampo/fisiología , Potenciales de Acción , Animales , Estimulación Eléctrica , Hipocampo/crecimiento & desarrollo , Ratas , Ratas EndogámicasRESUMEN
Adult rats underwent amygdala kindling after the administration of vehicle, flunarizine 20 mg/kg/day, or flunarizine 40 mg/kg/day. Stimuli were delivered thrice daily at current intensities twice after-discharge threshold (ADT). Flunarizine did not alter initial or post-kindling ADT and did not affect the latency (number of stimuli) to the first stage 5 seizure. Apart from a tendency to increase the latency between the first and the 4th stage 5 seizures, flunarizine had little if any effect on amygdala kindling in this protocol.
Asunto(s)
Flunarizina/uso terapéutico , Excitación Neurológica/efectos de los fármacos , Convulsiones/tratamiento farmacológico , Amígdala del Cerebelo , Animales , Ratas , Ratas EndogámicasRESUMEN
Aminophylline (A) is a proconvulsant in adult rats. We studied the effect of A on amygdala kindling in 15-day-old rat pups. Production of generalized seizures was significantly promoted by A at doses ranging from 10 to 100 mg/kg. Terminal status epilepticus (TSE) was produced in 33% of pups receiving 25 mg/kg A, 75% of pups receiving 50 mg/kg A, and 100% of pups receiving 100 mg/kg A. The number of stimuli needed to produce a stage 4-5 generalized seizure was significantly smaller in animals receiving 10 mg/kg A (5.7 +/- 3.4), 25 mg/kg A (3.4 +/- 2.4), 50 mg/kg A (1.9 +/- 1.4), or 100 mg/kg A (1.9 +/- 1.6) than in saline-treated controls (12.3 +/- 3.7) (P less than 0.001). In addition, 16% of pups receiving 50 mg/kg and 33% of pups receiving 100 mg/kg A and never stimulated developed TSE. These seizure-promoting effects of A in rat pups undergoing amygdala kindling are far more dramatic and occur at far lower doses than those previously reported in adults.
Asunto(s)
Aminofilina/farmacología , Amígdala del Cerebelo/fisiopatología , Convulsivantes/farmacología , Excitación Neurológica , Convulsiones/inducido químicamente , Factores de Edad , Animales , Relación Dosis-Respuesta a Droga , Ratas , Ratas Endogámicas , Convulsiones/fisiopatologíaRESUMEN
Although automated continuous performance tests (CPT) are gaining popularity as aids to the diagnosis of attention deficit disorder (ADD), little is known of their validity in this context. Our preliminary experience with a commercially available visual CPT indicated that as many as a third of children meeting the DMS-III criteria for ADD may score well enough on this measure to escape detection. We therefore analyzed the results of neuropsychological testing as well as CPT performance in 14 ADD children and six non-ADD children in an effort to determine whether CPT performance might reflect higher level cognitive variables other than attention and/or impulsivity. We found that those ADD children classified as "abnormal" on the basis of the CPT scored significantly below those classified as "normal" on measures of abstract reasoning and logical problem solving, simple verbal reasoning, nonverbal problem solving, and simple arithmetic skills. The non-ADD group contained a high proportion (83%) of subjects with CPT performance outside of the normal range. These data suggest that CPT may yield both false negative and false positive results when used as screening tools for ADD, and we recommend therefore that caution be used in their interpretation.
Asunto(s)
Trastorno por Déficit de Atención con Hiperactividad/diagnóstico , Adolescente , Niño , Femenino , Humanos , Masculino , Pruebas Neuropsicológicas , Análisis y Desempeño de TareasRESUMEN
We administered the go-no-go paradigm to 44 boys with attention deficit disorder (ADD) and 32 control subjects who did not have ADD. This task requires a subject to emit a simple motor response to one cue while inhibiting the response in the presence of another cue. Commission errors suggest impulsivity, and omission errors suggest inattention. ADD subjects made more total errors than did control subjects (p less than 0.03), and more ADD subjects made multiple errors (p less than 0.001). Within the ADD group, the nonhyperactive (ADDnoH) subjects were characterized by a high number of commission errors early, and significant improvement with practice (p less than 0.01). In contrast, the hyperactive ADD subjects (ADD/H) did not differ from control subjects in number of early commission errors, but differed from both control subjects and ADDnoH subjects in their failure to improve with practice. In addition, the incidence of omission errors was highest in the ADD/H group. This paradigm can be easily incorporated into the assessment of children with suspected ADD and provides an objective measure of inattention and impulsivity. Our data provide cognitive support for the empirical distinction between hyperactive and nonhyperactive children with ADD.
Asunto(s)
Trastorno por Déficit de Atención con Hiperactividad/psicología , Aprendizaje Discriminativo/fisiología , Adolescente , Trastorno por Déficit de Atención con Hiperactividad/diagnóstico , Niño , Señales (Psicología) , Humanos , Masculino , Pruebas NeuropsicológicasRESUMEN
We describe a patient who experienced focal cerebral and brainstem ischemia in the setting of postpartum eclampsia. Cerebral angiography showed spasm of large- and medium-caliber arteries. This case provides rare documentation that vasospasm may account for cerebral ischemia in eclamptic women with focal signs. This observation suggests that in such patients cerebral angiography may be informative and useful.