Classical estrogen receptor-signaling mechanisms involve estradiol binding to intracellular nuclear receptors [estrogen receptor-␣ (ER␣) and estrogen receptor-␤ (ER␤)] to promote changes in protein expression. Estradiol can also exert effects within seconds to minutes, however, a timescale incongruent with genomic signaling. In the brain, estradiol rapidly potentiates stimulated dopamine release in the striatum of female rats and enhances spontaneous rotational behavior. Furthermore, estradiol rapidly attenuates the K ϩ -evoked increase of GABA in dialysate. We hypothesize that these rapid effects of estradiol in the striatum are mediated by ER␣ located on the membrane of medium spiny GABAergic neurons. This experiment examined whether overexpression of ER␣ in the striatum would enhance the effect of estradiol on rotational behavior and the K ϩ -evoked increase in GABA in dialysate. Ovariectomized female rats were tested for rotational behavior or underwent microdialysis experiments after unilateral intrastriatal injections of a recombinant adeno-associated virus (AAV) containing the human ER␣ cDNA (AAV.ER␣) into the striatum; controls received either the same vector into areas outside the striatum or an AAV containing the human alkaline phosphatase gene into the striatum (AAV.ALP). Animals that received AAV.ER␣ in the striatum exhibited significantly greater estradiol-induced contralateral rotations compared with controls and exhibited behavioral sensitization of contralateral rotations induced by a low-dose of amphetamine. ER␣ overexpression also enhanced the inhibitory effect of estradiol on K ϩ -evoked GABA release suggesting that disinhibition of dopamine release from terminals in the striatum resulted in the enhanced rotational behavior.

The purine nucleoside adenosine is produced at increased levels in the tissues of solid cancers as a result of local hypoxia. Adenosine inhibits the cell-mediated anti-tumor immune response, promotes tumor cell migration and angiogenesis, and stimulates the proliferation of tumor cells. We examined the stimulatory effect of adenosine on DNA synthesis, cell cycle progression, and cell proliferation in MCF7 and T-47D breast carcinoma cell lines in culture, and identified factors that modulate the growth response. The ability of adenosine to stimulate DNA synthesis, as measured by the incorporation of [(3)H]thymidine, was independent of the total radioactivity of the [(3)H]thymidine up to 10 microCi/ml, total thymidine concentrations up to 100 microM, and the labeling interval. It was also not affected by the presence of low-molecular-weight compounds (such as thymidine and adenosine) in the serum used to supplement the medium. Adenosine stimulated DNA synthesis and cell proliferation with an EC(50) of 4-6 microM and a maximum response at 30-100 microM, when given as a single addition. The stimulatory effect of adenosine involved progression through the cell cycle and a genuine increase in cell number, in the absence of significant apoptotic or necrotic cell death. The mitogenic effect of adenosine was dependent upon the culture cell density, with an optimum adenosine response at around 50% of confluent density. The response was also highly dependent upon the form of the serum addition to the growth medium, with the best response elicited in the presence of low concentrations of nonfetal bovine serum, although adenosine was mitogenic under standard culture conditions. The effects of serum supplementation and cell density were not due to differences in the rate of adenosine metabolism by either serum or cellular enzymes, but appeared to result from changes in the sensitivity to adenosine of the cell population in response to environmental cues. We, therefore, find that adenosine is consistently mitogenic for human breast carcinoma cells, and that the [(3)H]thymidine incorporation assay is a valid measure of this response. The data are consistent with the stimulatory effect of adenosine on cell proliferation being modulated by the local cellular environment.

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Sensory cues from male rats, such as odours and vaginal-cervical stimulation (VCS), play a modulatory role in female rat sexual behaviour. For example, exposure to male odours and VCS appears to be at least partially responsible for increases in sexual behaviour following repeated mating of oestradiol-primed female rats. Although there is evidence that VCS influences sexual behaviour via a ligand-independent progestin receptor (PR)-dependent mechanism, the mechanism by which odours influence sexual behaviour is not known. We tested the hypothesis that, similar to VCS, the effects of male odours on sexual behaviour are mediated by progestin receptors. Female rats were injected with the progestin antagonist, RU486, or oil vehicle and were then exposed to male-soiled bedding or clean bedding. Although exposure to male-soiled bedding resulted in higher levels of Fos immunoreactivity in brain areas associated with female sexual behaviour, the progestin antagonist did not reduce this effect. Furthermore, there was minimal coexpression of odour-induced Fos and progestin receptors in brain areas associated with female sexual behaviour. Together, these results suggest that the effects of male odours are not mediated by a PR-dependent mechanism. Therefore, we tested the hypothesis that oestrogen receptor (ER)-containing cells are involved in the effects of olfactory cues. Although there was virtually no coexpression of ERb and odour-induced Fos in brain areas associated with female sexual behaviour, exposure to male odours slightly increased the number of cells coexpressing ERa and odour-induced Fos in the posterodorsal medial amygdala. Although, these results do not support the hypothesis that the effects of odours are mediated by a PR-dependent mechanism, they suggest that integration of male odours and hormonal cues may occur in ERa-containing cells in the posterodorsal medial amygdala.In oestrous cycling female rats, sexual behaviour is induced by an increase in oestradiol followed by an increase in progesterone (1, 2). Sexual behaviour is prevented by treatment with oestrogen or progestin antagonists, suggesting that the behaviour is mediated by activation of intracellular steroid receptors (3). Although steroid hormones are critical for the induction of female sexual behaviour, sensory cues received during mating, such as vaginal-cervical stimulation (VCS) and male odours, also modulate the behaviour. For example, VCS from intromissions and ejaculations increases return latencies during paced mating (4) and accelerates oestrous termination (5, 6). In addition, male olfactory cues seem to enhance sexual receptivity, because removal of the vomeronasal organ reduces sexual receptivity in female rats on the day of proestrus (7,8), as well as in ovariectomized rats treated with oestradiol and progesterone (8).Sexual receptivity is also enhanced in the absence of progesterone when oestradiol-primed female rats are repeatedly mated with male rats (9-15). Sensory cues received during mating also contribute to this e...