Ventromedial hypothalamic damage and sexual proceptivity in female rats.
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Animals↗
Biomedical subjects
A S Clark
Publications and source records attributed to A S Clark.
Comparative effects of oestrogen and a progestogen on bone loss in postmenopausal women.
1. The value of progestogen therapy in the prevention of postmenopausal bone loss was assessed in 30 women, by a preliminary randomized controlled trial of gestronol or mestranol, in comparison with a placebo. 2. When the skeletal response was measured by photon absorptiometry, bone mineral loss was prevented by both the oestrogen and the progestogen. 3. We confirm that mestranol significantly reduced the urinary output of hydroxyproline-containing peptide, but this did not occur during gestronol therapy, suggesting that progestogen has a different action on bone, perhaps stimulating bone formation.
Adult↗
Health and social services.
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Child Guidance↗
Estrogen formation in the mammalian brain: possible role of aromatase in sexual differentiation of the hippocampus and neocortex.
Recent studies suggest that sex differences in cognitive function may involve effects of circulating androgens on the developing cerebral cortex and hippocampus. The mechanism of these effects is not understood. In rhesus monkeys, aromatase activity is present in the hippocampus and several areas of the cerebral cortex during late fetal and early postnatal life. Similarly, work in rats and mice indicates that the hippocampus and cerebral cortex may be capable of estrogen biosynthesis during early development. These results are consistent with the hypothesis that the actions of androgens on the developing cerebral cortex and hippocampus may involve local estrogen-mediated effects similar to those responsible for differentiation of the hypothalamic mechanisms controlling reproductive function.
Animals↗
Paced mating behavior in the naturally cycling and the hormone-treated female rat.
During a sexual encounter with a male rat, a female rat will display both receptive (lordosis) and proceptive (hopping, darting, and ear-wiggling) behaviors. Additionally, if mating occurs in an environment where the female rat may approach and withdraw from the male rat, she will control the timing of the receipt of mounts, intromissions, and ejaculations. This temporal patterning by the female rat is known as paced mating behavior. The present experiment compared paced mating behavior in rats during an intact, proestrous phase and an ovariectomized phase, during which they were treated with estradiol benzoate (10 microg per rat) and progesterone (0.5 mg per rat). Though no differences in sexual receptivity were observed across the two phases, patterns of paced mating behavior were found to differ. Specifically, female rats exhibited significantly longer contact-return latencies when hormone treated than when intact.
Animals↗
GABA-immunoreactive neurons in the mediodorsal nucleus of the monkey thalamus.
The mediodorsal nucleus of the thalamus is an important component of the brain's circuitry for memory 9,20 and yet surprisingly little is known of its intrinsic organization. In the present study we have examined the distribution, spatial relationships and morphology of gamma-aminobutyric acid (GABA)-containing cells within the magnocellular and parvocellular subdivisions of the mediodorsal nucleus. These subdivisions have anatomically and functionally distinct connections with the orbital (limbic) and dorsolateral (association) areas of the prefrontal cortex, and accordingly, we investigated whether there were corresponding differences in their local circuit organization. Our findings show that round or ovoid GABA-immunoreactive neurons were abundant in both subdivisions. However, these neurons were larger in diameter in the magnocellular aspect (mean diameter = 10.4 +/- 0.1 micron) than in the parvocellular moiety (mean diameter = 9.9 +/- 0.1 micron) and the intensity of reactivity was also greater for the magnocellular neurons. Comparison of the densities of GABA-immunoreactive neurons revealed not only a greater density of neurons in the parvocellular division but also that the proportion of all neurons which were GABA-containing was greater in this region. These differences in the morphology and density of inhibitory local circuit neurons may contribute to the functional duality of prefrontal cortex innervated by these thalamo-cortical pathways. Certain qualitative features were common to both subdivisions; thus GABA-immunoreactive neurons were found in small clusters throughout the magnocellular and parvocellular divisions of the mediodorsal nucleus and, in addition, regions with few or no GABA-immunoreactive cells were often surrounded by strings of GABA-containing neurons.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗