Evidence against alpha2-adrenoceptor involvement in the regulation of rat melatonin synthesis by ambient lighting

Discovery of candidate genes and pathways that may help explain fertility cycle stage dependent post-resection breast cancer outcome

Breast cancer relapse and death occur more often and sooner among young pre-menopausal women. Breast cancer resected during luteal phase cures about a quarter more women than if the operation is performed during follicular phase. We have identified candidate breast cancer gene signatures that may point to the potential mechanisms of cycle stage-dependent surgical cure. We performed whole murine genome microarrays on mammary tumors resected during pre-ovulatory (diestrus, follicular) and post-ovulatory (estrus, luteal) phases of the estrous cycle with known post-surgical cure or relapse (pulmonary metastasis) outcome. A set of genes whose expressions are differentially modulated by fertility cycle stage of tumor resection and also associate with prognosis were identified. These identified genes were validated by qRT-PCR. From two independent microarray studies, we identified 90 genes in mammary tumors whose expressions change significantly (up to 100-fold) across the estrous cycle, 69 genes that are associated with cure/relapse independent of cycle stage at resection, and 24 genes that change significantly (up to 12-fold) across the estrous cycle and also associate with the outcome. The mRNA expression patterns of these 24 identified genes were 100% validated by qRT-PCR in the same samples. We have identified candidate breast cancer genes and pathways that may point to the potential mechanisms by which the post-resection breast cancer outcome is influenced by the menstrual cycle phase of cancer resection. Since human breast cancer outcome is influenced by the menstrual cycle phase of breast cancer resection, we consider this study in a mouse breast cancer model to be a proof of principle that such signatures may well exist in human premenopausal breast cancer. It remains to be determined in human breast cancer whether woman to woman and/or tumor to tumor variability will mask cycle phase dependent and outcome predictive genomic signatures in human premenopausal breast cancer. The pathways identified by these studies are potential targets for the development of peri-surgical neoadjuvant therapies, which may delay or prevent relapse by preventing dormant micrometastatic tumor cells from escaping that dormant state post-operatively.

Adrenergic response patterns in vas deferens isolated from rats under diurnal rhythms

The aim of this study was to verify, by means of functional methods, whether the circadian rhythm changes adrenergic response patterns in the epididymal half of the vas deferens isolated from control rats as well as from rats submitted to acute stress. The experiments were performed at 9:00 a.m., 3:00 p.m., 9:00 p.m., and 3:00 a.m. The results showed a light-dark dependent variation of the adrenergic response pattern on organs isolated from control as well as from stressed rats. In the control group, only the phenylephrine sensitivity was changed throughout the circadian rhythm. Under the stress condition, both norepinephrine and phenylephrine response patterns were changed, mainly during darkness. The maximal contractile response to both alpha- and beta-agonist and alpha1-agonist was increased in the dark phase, corresponding to high plasmatic concentrations of endogenous melatonin. The vas deferens isolated from stressed rats during the light phase simultaneously incubated with exogenous melatonin showed the same pattern of response obtained in the dark phase, thus indicating a peripheric action of melatonin on this organ. Therefore, the circadian rhythms are important to the adrenergic response pattern in rat vas deferens from both control and stressed rats. In conclusion, we suggest a melatonin modulation on alpha1-postsynaptic adrenergic response in the rat vas deferens.

Evidence for central alpha(2)-adrenergic modulation of rat pineal melatonin synthesis

This study was performed to distinguish central and peripheral alpha(2)-adrenoceptors in the inhibition of rat pineal melatonin synthesis. The rats received lipo- or hydrophilic alpha(2)-adrenoceptor ligand injections at middark; after 1 or 2 h the pineal melatonin contents were measured. The lipophilic agonist medetomidine (100 microg/kg s.c.) suppressed the melatonin contents significantly, while the hydrophilic agonists ST-91 and p-aminoclonidine (10 or 100 microg/kg i.v.) did not. The suppression by medetomidine was counteracted by the lipophilic antagonist yohimbine (0.3-3.0 mg/kg i.p.) but not by the hydrophilic antagonist L-659,066 (1-10 mg/kg i.v.). In conclusion, the suppression of nocturnal melatonin synthesis by alpha(2)-adrenoceptor agonists is mainly of central origin.