Age-Related Changes in Grooming Behavior and Motor Activity in Female Rats
Departamento de Farmacología, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, Argentina. Physiology & Behavior
(Impact Factor: 2.98).
06/1999; 66(3):481-4. DOI: 10.1016/S0031-9384(98)00314-X
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.
Available from: Jeng-Rung Chen
- "In mammals, females are uniquely endowed with sex cycle that displayed cyclic physiological changes in association with profound sensory and motor influences (e.g., Bonifazi et al. 2004). Behavioral study of female rats shows that grooming, rearing, and motor activity change cyclically during estrous cycle suggesting that brain areas such as the primary cortices may be affected during female sex cycle as well (Scimonelli et al. 1999). To investigate this, we studied the dendritic arbors of layer III and layer V pyramidal neurons of the primary sensory and motor cortices (primary sensorimotor cortex) of adult female rats during different stages of the estrous cycle by using intracellular dye injection and 3-dimensional neuronal reconstruction. "
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ABSTRACT: Adult dendritic arbors and spines can be modulated by environment and gonadal hormones that have been reported to affect also those of hippocampal and prefrontal cortical neurons. Here we investigated whether female gonadal hormones and estrous cycle alter the dendrites of primary cortical neurons. We employed intracellular dye injection in semifixed brain slices and 3-dimensional reconstruction to study the dendritic arbors and spines of the major cortical output cells, layer III and V pyramidal neurons, during different stages of the estrous cycle. Dendritic spines of both pyramidal neurons were more numerous during proestrus than estrus and diestrus, whereas dendritic arbors remained unaffected. Ovariohysterectomy (OHE) reduced dendritic spines by 24-30% in 2 weeks, whereas subcutaneous estrogen or progesterone supplement restored it to normal estrous/diestrous level in 14 days; neither treatment affected the dendritic arbors. Reduction of dendritic spines following OHE was associated with decrease of PSD-95 suggesting decrease of excitatory synapses. Thus, fluctuation of gonadal hormones during the female sex cycle is likely to modulate primary cortical functions and loss of gonadal hormones for instance following menopause might compromise cortical function, and the effect could be reversed by exogenous female sex hormones.
Available from: Yueh-Jan Wang
- "Another advantage of this methodology is that by preincubating the slice in 4=,6-diamidino-2-phenyl-indole (DAPI) that reveals cell nuclei, cortical layers and their neurons could be distinguished and neurons, well-separated from each other, could be selected and filled individually under visual guidance of a fluorescence microscope (Wang et al., 1996, 2002; Chen et al., 2003). To find out whether cortical neuronal morphological changes underlie the alterations of behavior and motor performance associated with aging (Scimonelli et al., 1999), we concentrated on studying the sensorimotor cortex of aged rats since the function of their primary sensorimotor cortex is likely to be compromised. "
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ABSTRACT: We studied the cytoarchitecture and dendritic arbors of the output neurons of the sensorimotor cortex of aged rats and found that although individual cortical layer became thinner, the overall cytoarchitecture and neuron densities remained comparable to those of young adults. To find out whether aging affects cortical outputs we studied the soma-dendritic arbors of layers III and V pyramidal neurons, main output neurons of the cerebral cortex, using brain slice intracellular dye injection technique. With a fluorescence microscope, selected neurons were filled with fluorescence dye under visual guidance. Injected slices were resectioned into thinner sections for converting the injected dye into non-fading material immunohistochemically. The long apical dendritic trunk and branches could be routinely revealed. This allowed us to reconstruct and study the dendritic arbors of these neurons in isolation in 300-microm-thick dimension. Analysis shows that their cell bodies did not shrink, but the densities of spines on dendrites and the total dendritic length significantly reduced. Among spines, those with long thin stalks thought to be involved in memory acquisition appeared to be reduced. These could underlie the compromise of sensorimotor functions following aging.
Available from: Rebecca Craft
- "Sex differences in basal activity are sometimes but not always reported in rodents; when a sex difference is reported, females are found to be more active than males (e.g., Blizard et al., 1975; Beatty, 1979; Jones et al., 1990; van Haaren & Meyer, 1991; Craft et al., 1996; Craft & Bernal, 2001; but see Forgie & Stewart, 1994; Pearl et al., 1997; Sell et al., 2000; Schindler & Carmona, 2002). Although estrous cycle-related fluctuations in activity have been reported previously (e.g., Scimonelli et al., 1999), other laboratories report no significant differences (e.g., Quinones-Jenab et al., 1999; Sell et al., 2000; present study). Becker (e.g., Becker et al., 1987) has shown that sensorimotor performance (coordination) rather than simply the amount of movement per se changes across the estrous cycle; another study also showed that estrousrelated changes in movement depend on the type of movement measured, and may not be seen when only horizontal activity is assessed (Steiner et al., 1981). "
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ABSTRACT: Sex differences in reinforcing, analgesic and other effects of opioids have been demonstrated; however, the extent to which sex differences in motoric effects of opioids contribute to apparent sex differences in their primary effects is not known. The goal of this study was to compare the effects of the prototypic mu opioid agonist morphine on locomotor activity in male vs. female rats. Saline or morphine (1-10 mg/kg) was administered s.c. to adult Sprague-Dawley rats, which were placed into a photobeam apparatus for 3-5 h to measure activity. Modulation of morphine's effects by gonadal hormones and by handling (either during the test session or for 4 days before the test session) were examined. Morphine initially suppressed and later increased locomotor activity in both sexes relative to their saline-injected controls, but males were more sensitive than females to the initial locomotor suppressant effect of morphine. Intermittent, brief handling during the 3-h test session blunted morphine-induced locomotor activation in both sexes. Females in proestrus were the most sensitive to morphine's locomotor-stimulant effect, with females in estrus showing the least response to morphine. Gonadectomized (GDX) males with or without testosterone were equally sensitive to morphine's effects, whereas GDX females treated with estradiol showed a blunted response to morphine's effects, similar to intact females in estrus. Brief handling on each of 4 consecutive days pre-test attenuated morphine's locomotor suppressant effect in males but had no effect in females, thereby eliminating the sex difference. These data suggest that sex differences in morphine's effects on locomotor activity can be attributed to gonadal hormones in females, and to differential stress-induced modulation of morphine's effects in males vs. females.
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