Age-related changes in grooming behavior and motor activity in female rats
ABSTRACT The influence of hormonal status and the age of the rat on the expression of grooming behavior and motor activity were studied. Grooming, locomotion, and rearing were measured in young (4-months-old), adult (6-8-months-old), and old (18-months-old) female rats, during the estrous cycle. These behavioral performances were influenced by the hormonal changes that occur in young and adult female rats during the estrous cycle. In old rats there were no significant differences among the different days of the estrous cycle. A significant age-related decrease in grooming behavior and motor activity was also found. Locomotion and rearing were the parameters most affected by age. These findings could be related to: (a) the gonadal hormonal status, which appears to be able to modulate behavioral responses; and (b) the age-related changes, which may affect the normal display of these behaviors. The possible role of central peptidergic, cholinergic, and dopaminergic neural systems is discussed.
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ABSTRACT: Brain structures and functions are increasingly recognized to be directly affected by gonadal hormones, which classically determine reproductive functions and sexual phenotypes. In this regard, we found recently that ovariectomy trimmed the dendritic spines of female rat primary somatosensory cortical neurons and estradiol supplement reversed it. Here, we investigated whether in the male androgen also has a cortical modulatory effect. The dendritic arbors and spines of rat somatosensory cortical pyramidal neurons were studied following intracellular dye injection and three-dimensional reconstruction. Dendritic spines, but not length, of the layers III and V pyramidal neurons were found reduced at 2 weeks and rebounded slightly at 4 weeks and further at 8 and 24 weeks following castration, which, however, remained significantly fewer than those of the intact animals. Two weeks of osmotic pump-delivered testosterone treatment to animals castrated for 4 weeks replenished serum testosterone and reversed the densities of dendritic spines on these neurons to control animal levels. Androgen receptor appears to mediate this effect as its antagonist flutamide reduced the dendritic spines of normal adult rats while causing a mild feedback surge of serum testosterone. On the other hand, blocking the conversion of testosterone to estrogen with the aromatase inhibitor anastrozole failed to alter the dendritic spine densities in male adult rats. In conclusion, these results support our hypothesis that testosterone acts directly on the androgen receptor in males to modulate the dendritic spines of somatosensory cortical output neurons.Brain Structure and Function 01/2013; DOI:10.1007/s00429-012-0465-7 · 4.57 Impact Factor