RESUMEN
Ovarian hormones alter spine density of hippocampal granule and pyramidal cells in young adult and aging female rats (P. Miranda, C. L. Williams, & G. Einstein, 1999; C. S. Woolley, 1998). The present study used a delayed matching-to-place version of the water maze to investigate a behavioral correlate of these hormone-induced changes in hippocampal connectivity in 3- and 8-month-old female rats. When primed with 10-microg injections of estradiol 72 and 48 hr before testing, the memory retention of ovariectomized rats was improved compared with retention after priming with oil. A single injection of progesterone maintained this enhancement if testing occurred within 8 hr of the progesterone injection but not if testing occurred more than 24 hr after the progesterone injection. These findings indicate that estradiol and progesterone alter memory retention and suggest that these changes may be the result of hormone-induced increases in hippocampal connectivity.
Asunto(s)
Estradiol/farmacología , Aprendizaje por Laberinto/efectos de los fármacos , Progesterona/farmacología , Retención en Psicología/efectos de los fármacos , Animales , Dendritas/efectos de los fármacos , Femenino , Hipocampo/efectos de los fármacos , Red Nerviosa/efectos de los fármacos , Neuronas/efectos de los fármacos , Células Piramidales/efectos de los fármacos , Ratas , Ratas Sprague-DawleyRESUMEN
The authors report that the expression of a conditioned odor aversion is impaired in preweanling rats when they are conditioned on Postnatal Day 12 and tested under the influence of scopolamine hydrobromide (0.2 or 0.5 mg/kg, intraperitoneal) after a 48-hr, but not after a 2-hr, retention interval (Experiment 1). This effect of scopolamine is not dependent on maturation of the cholinergic system between Days 12 and 14 (Experiment 2), nor is it due to peripheral mechanisms (Experiment 3). When pups are reexposed to the unconditioned stimulus (footshock) before drug administration, performance on the 48-hr retention test is not impaired by scopolamine (Experiment 4). These findings demonstrate that the cholinergic system may be critical for the retrieval and expression of long-term or weak memories in young rats. However, the expression of active memories (recent or recently reactivated) may not be dependent on the cholinergic system to the same extent as is the expression of inactive memories.
Asunto(s)
Animales Lactantes , Condicionamiento Clásico/efectos de los fármacos , Antagonistas Muscarínicos/farmacología , Odorantes , Refuerzo en Psicología , Retención en Psicología/efectos de los fármacos , Escopolamina/farmacología , Factores de Edad , Análisis de Varianza , Animales , Animales Lactantes/crecimiento & desarrollo , Animales Lactantes/psicología , Encéfalo/efectos de los fármacos , Encéfalo/crecimiento & desarrollo , Conducta de Elección/efectos de los fármacos , Fibras Colinérgicas/fisiología , Condicionamiento Clásico/fisiología , Electrochoque , Femenino , Masculino , Ratas , Ratas Sprague-Dawley , Retención en Psicología/fisiología , Factores de TiempoRESUMEN
The study of navigational ability in humans is often limited by the restricted availability and inconvenience of using large novel environments. In the present study we use a computer-generated virtual environment to study sex differences in human spatial navigation. Adult male and female participants navigated through a virtual water maze where both landmarks and room geometry were available as distal cues. Manipulation of environmental characteristics revealed that females rely predominantly on landmark information, while males more readily use both landmark and geometric information. We discuss these results as a possible link between recent human research reporting hippocampal activation in spatial tasks and animal work showing sex differences in both spatial ability and hippocampal development.