RESUMO
Juvenile rats with kaolin-induced hydrocephalus have reduced brain injury if treated with nimodipine or magnesium sulfate. Experiments were conducted to determine if the neuroprotective effects could be replicated in neonatal rats with experimental hydrocephalus at an age comparable to prematurely born humans. In a blinded and randomized manner, drugs were administered for 14 days beginning 7 days after induction of hydrocephalus. Nimodipine was given twice daily by subcutaneous injections. Daily doses greater than 38 mg/kg of body weight were fatal. Daily doses of 3.8 to 30 mg/kg were not associated with behavioral, structural, or biochemical improvements. Magnesium chloride was administered via daily subcutaneous minipump infusion (0.87 or 1.74 mM/kg) along with twice daily injections of 0.74 or 1.48 mM/kg. Magnesium sulfate was administered by twice daily subcutaneous doses of 1.54 or 7.72 mM/kg. Sedation occurred, but there was no statistically significant protection in regard to behavior, brain structure, or brain composition in any of the magnesium experiments. Developmental alterations in calcium channels of the neonatal rat brain could account for differences from prior experiments in young hydrocephalic rats.
Assuntos
Dano Encefálico Crônico/tratamento farmacológico , Bloqueadores dos Canais de Cálcio/farmacologia , Canais de Cálcio/efeitos dos fármacos , Hidrocefalia/tratamento farmacológico , Compostos de Magnésio/farmacologia , Fármacos Neuroprotetores/farmacologia , Animais , Animais Recém-Nascidos , Encéfalo/efeitos dos fármacos , Encéfalo/patologia , Encéfalo/fisiopatologia , Dano Encefálico Crônico/etiologia , Dano Encefálico Crônico/fisiopatologia , Bloqueadores dos Canais de Cálcio/uso terapêutico , Canais de Cálcio/metabolismo , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Feminino , Hidrocefalia/induzido quimicamente , Hidrocefalia/complicações , Bombas de Infusão , Caulim/efeitos adversos , Ventrículos Laterais/patologia , Cloreto de Magnésio/farmacologia , Cloreto de Magnésio/uso terapêutico , Compostos de Magnésio/uso terapêutico , Sulfato de Magnésio/farmacologia , Sulfato de Magnésio/uso terapêutico , Masculino , Fibras Nervosas Mielinizadas/efeitos dos fármacos , Fibras Nervosas Mielinizadas/patologia , Fármacos Neuroprotetores/uso terapêutico , Nimodipina/farmacologia , Nimodipina/uso terapêutico , Ratos , Ratos Sprague-Dawley , Taxa de Sobrevida , Resultado do TratamentoRESUMO
The effects of divided attention were examined in younger adults (M = 23 years) and older adults (M = 64 years) who searched for traffic signs in digitized images of traffic scenes. Sign search was executed under single-task and dual-task conditions in scenes containing either small or large amounts of visual clutter. For both age groups, clutter and the secondary task had additive effects on search accuracy, speed, and oculomotor involvement. Compared with the younger adults, older adults were less accurate, especially with high-clutter scenes, were slower to decide that a target sign was not present, and exhibited a marginally greater divided-attention effect on reaction times. They exhibited longer fixations in the divided-attention condition, in which they also showed a disproportionate reduction in recognition memory for the content of the secondary task. Actual or potential applications of this research include methods for evaluating the distraction of conversations and safety implications of conversation on visual search behavior.