UVM Theses and Dissertations
Format:
Print
Author:
Cherian, Suraj
Dept./Program:
Biology
Year:
2014
Degree:
Ph. D.
Abstract:
In rodents, many social behaviors are driven by the sense of smell. The vomeronasal organ (VNO), part of the accessory olfactory system mediates many of these chemically driven behaviors. The VNO is heavily vascularized and is readily accessible to circulating peptide or steroid hormones. Potentially, this allows circulating hormones to modulate the output of the primary sensory neurons in the VNO, the vomeronasal sensory neurons (VSNs). Based on this, we hypothesized that steroid hormones, in particular 17[beta]-estradiol, would modulate activity of vomeronasal sensory neurons (VSNs). Here, we show that estrogen receptors, GPR30 and ER[alpha] were present in VSNs and that estradiol may be synthesized locally in the VNO. Our results also showed that 17[beta]-estradiol decreased responSes of isolated VSNs to dilute urine, a potent natural stimulus, with respect to current amplitudes and depolarization. Further 17[beta]-estradiol increased the latency of the first action potential (AP) and the AP amplitude. Additionally, calcium responses to sulfated steroids (present in the low molecular weight fraction of urine) that act as ligands for apical vomeronasal receptors were decreased by 17[beta]-estradiol.
Voltage gated conductances underlie action potentials. Key ion channels underlying action potentials include but are not limited to voltage gated sodium, calcium and potassium conductances. Our whole cell patch clamp results showed that estradiol did not alter the activation properties or fast inactivation kinetics of voltage gated sodium currents. Additionally, estradiol did not alter activation properties of voltage gated potassium currents. We used calcium imaging to determine if any high potassium elicited calcium transients which are primarily mediated by voltage gated calcium channels were altered by estradiol and our results show that calcium transients were altered. In conclusion, we show that estradiol modulates odorant responses mediated by VSNs and hence paves the way for future studies to better understand the mechanisms by which odorant mediated behavior is altered by endocrine status of the animal.
Voltage gated conductances underlie action potentials. Key ion channels underlying action potentials include but are not limited to voltage gated sodium, calcium and potassium conductances. Our whole cell patch clamp results showed that estradiol did not alter the activation properties or fast inactivation kinetics of voltage gated sodium currents. Additionally, estradiol did not alter activation properties of voltage gated potassium currents. We used calcium imaging to determine if any high potassium elicited calcium transients which are primarily mediated by voltage gated calcium channels were altered by estradiol and our results show that calcium transients were altered. In conclusion, we show that estradiol modulates odorant responses mediated by VSNs and hence paves the way for future studies to better understand the mechanisms by which odorant mediated behavior is altered by endocrine status of the animal.