Biomedical subjects

Noah J Sandstrom

Publications and source records attributed to Noah J Sandstrom.

5 recordsLinked to original sources

PubMed2005

Testosterone modulates performance on a spatial working memory task in male rats.

Gonadal hormones have been shown to modulate memory retention in female rats. The current experiments examine the role of testicular hormones in modulating the performance of male rats on two spatial water maze tasks. In the first study, castrated and intact rats were trained on the visible platform and hidden platform versions of the Morris water maze task. Castration did not affect performance on either version of this reference memory task with castrated and intact rats demonstrating similar performance both during acquisition and on post-training probe trials. In the second experiment, castrated and intact rats were tested on a delayed-matching-to-place version of the water maze. Rats received a series of trial pairs in the maze with a hidden platform located in the same pool location on the exposure and retention trials of each pair; between pairs of trials, however, the platform was repositioned to a novel pool location. The interval between trials was either 10- or 60-min and memory retention, taken as the difference between the pathlengths on the exposure and retention trials, declined as the interval increased. Relative to intact males, castrated males demonstrated impaired working memory retention at 60-min but not at 10-min retention intervals. This interval-dependent impairment in working memory retention was reversed by physiologic levels of testosterone replacement. These findings indicate that castration does not significantly affect acquisition or probe trial performance on a classic reference memory task but does impair spatial working memory retention, an effect that is reversed by exogenous testosterone.

Analysis of Variance↗

PubMed2005

Isolation stress during the third postnatal week alters radial arm maze performance and corticosterone levels in adulthood.

Stressful experiences during development cause long-lasting changes in neuroendocrine systems as well as lasting changes in behavior. The present study examines the long-term consequences of daily periods of social isolation during the third postnatal week on radial arm maze performance in adulthood. Male rat pups were either isolated for 6 h per day between postnatal days 15-21 or remained in the home cage. This manipulation caused a significant increase in plasma corticosterone during the isolation period. As adults, these animals were tested on a 12-arm radial arm maze. Rats that experienced social isolation during development made more working memory errors during initial acquisition but reached an asymptotic level of performance comparable to controls. The pattern of reference memory errors across testing was comparable to the pattern of working memory errors, though the difference between isolated and control animals was not significant. Blood samples taken in adulthood revealed that social isolation during development results in an long-term elevation in plasma corticosterone levels. These findings indicate that isolation stress during the third week of life leads to lasting impairments in cognition and HPA axis activity and suggest a potential alteration in hippocampal function.

Analysis of Variance↗

PubMed2005

Sex differences in the long-term effect of preweanling isolation stress on memory retention.

Social experiences during development can powerfully modulate later neuroendocrine and behavioral system. In the present study, male and female rat pups experienced daily bouts of social isolation for 6 h per day or control conditions during the third postnatal week. Performance on a 12-arm radial maze with 8 arms consistently baited with food reward was examined in adulthood. During the social isolation, both male and female pups exhibited a significant increase in plasma corticosterone levels. When tested on the radial arm maze as adults, the performance of female rats that had experienced social isolation during development was not affected; however, male rats in the isolation condition initially exhibited impairments in working memory but not reference memory. Despite achieving comparable asymptotic levels of performance on the maze, male rats that experienced social isolation during the third week demonstrated disruption in working memory retention when radial arm maze trials were interrupted after the fourth arm choice. Thus, while male rats that experience social isolation during the third week of life eventually perform comparably to controls on the standard radial arm maze task, their ability to retain information over a delay remains impaired. These findings highlight an important sex difference in the long-term effects of stress during this period of late preweanling development.

Age Factors↗

PubMed2004

Spatial memory retention is enhanced by acute and continuous estradiol replacement.

Estradiol replacement to ovariectomized female rats causes dramatic changes in hippocampal structure and function as well as in performance on hippocampally dependent tasks. Using a delayed matching-to-place version of the water maze, the present study examines the time course of estradiol-induced enhancements in memory retention as well as the effectiveness of acute and continuous patterns of replacement. One 10-microg injection of estradiol administered on each of two successive days resulted in significant improvements in memory retention that persisted for approximately 4 days following the second injection. When estradiol administration continued for 10 consecutive days, these improvements in memory retention persisted. These findings indicate that estradiol replacement can improve memory retention and that these improvements can be maintained by continuous replacement for at least 10 days.

Analysis of Variance↗

PubMed2002

Prenatal choline supplementation increases NGF levels in the hippocampus and frontal cortex of young and adult rats.

Female Sprague-Dawley rats received approximately 300 mg/kg per day of choline chloride through their drinking water on days 11 of pregnancy through birth and the level of nerve growth factor (NGF) in the hippocampus and frontal cortex of their male offspring was measured at 20 and 90 days of age. Prenatal choline supplementation caused significant increases in hippocampal NGF levels at 20 and 90 days of age, while levels of NGF in the frontal cortex were elevated in choline-supplemented rats at 20 days of age, but not 90 days of age. These results suggest that increases in NGF levels during development or adulthood may be one mechanism underlying improvements in spatial and temporal memory of adult rats exposed to elevated levels of choline chloride perinatally.

Aging↗