Biology subjects

Cornil, C. A.

Publications and source records attributed to Cornil, C. A..

2 recordsLinked to original sources

bioRxiv2023

Role of membrane estrogen receptor alpha on the positive feedback of estrogens on LH secretion

Estrogens act through nuclear and membrane-initiated signaling. Estrogen receptor alpha (ER) is critical for reproduction, but the relative contribution of its nuclear and membrane signaling is unclear. To address this question, we used two complementary approaches: estetrol (E4) a natural estrogen described to act as an agonist of nuclear ER and a mER antagonist and the C451A-ER mouse lacking mER. E4 dose-dependently blocks ovulation in female rats, but the mechanism underlying this effect is unknown. To determine whether E4 acts centrally to control ovulation, we tested its effect on the positive feedback of estradiol (E2) on LH secretion. In ovariectomized females chronically exposed to a low dose of E2, estradiol benzoate (EB) alone or combined with progesterone (P) induced a LH surge and the associated increase in the number of activated kisspeptin (Kp) and gonadotropin-releasing hormone (GnRH) neurons. However, E4 blocked these effects of EB when provided alone, but not when combined to P. These results indicate that E4 blocked the induction of the positive feedback and the associated neuronal activation in the absence of P, suggesting an antagonistic effect of E4 on mER as shown in peripheral tissues. In parallel, C451A-ER females do not show a pre-ovulatory LH surge and the associated activation of Kp and GnRH neurons in response to EB unless they are treated with P. The similarity of the responses of C451A-ER mice and wild-type females treated with E4 supports a role for membrane-initiated estrogen signaling in the EB-induced LH surge.

neuroscience↗

bioRxiv2021

Perineuronal nets in HVC and plasticity in male canary song

Songbirds learn their vocalizations during developmental sensitive periods of song memorization and sensorimotor learning. Some seasonal songbirds, called open-ended learners, recapitulate transitions from sensorimotor learning and song crystallization on a seasonal basis during adulthood. In adult male canaries, sensorimotor learning occurs each year in autumn and leads to modifications of the syllable repertoire during successive breeding seasons. We previously showed that perineuronal nets (PNN) expression in song control nuclei decreases during this sensorimotor learning period. Here we explored the causal link between PNN expression in adult canaries and song modification by enzymatically degrading PNN in HVC, a key song control system nucleus. Three independent experiments identified limited effects of the PNN degradation in HVC on the song structure of male canaries. They clearly establish that presence of PNN in HVC is not required to maintain general features of crystallized song. Some suggestion was collected that PNN are implicated in the stability of song repertoires but this evidence is too preliminary to draw firm conclusions and additional investigations should consider producing PNN degradations at specified time points of the seasonal cycle. It also remains possible that once song has been crystallized at the beginning of the first breeding season, PNN no longer play a key role in determining song structure which could be tested by treatments with ChABC at key step in ontogeny. It would in this context be important to develop multiple stereotaxic procedures allowing the simultaneous bilateral degradation of PNN in several song control nuclei for extended periods.

neuroscience↗