Odorants are detected by olfactory receptor neurons (ORNs) that project to the antennal lobe (AL), the first olfactory neuropil in the insect brain, where they make synaptic contacts with: i) projection neurons (PNs), that constitute the output of the AL; and ii) local neurons (LNs) that form a dense network of lateral interactions within the AL. The main goal of this project is to study the role of the LNs in odor representation using Drosophila melanogaster.
On a first approach we downregulated the expression of GABA-A receptors in PNs using RNAi and performed calcium imaging of odor-elicited activity in the AL. We found that constitutive reduction of the expression of the Rdl receptor subunit produced a series of compensations that resulted in the emergence of new inhibitory interactions. This result suggested the existence of a strong developmental plasticity in the AL.
As a second approach, we aim to acutely and reversibly block the activity of LNs. In that sense we plan to use shibire, a temperature sensitive mutant, to silence the LNs. Up to now, we tested the effect that raising the temperature of the flies has on odorant evoked activity at the AL. Preliminary results show that shifting temperature from 22 to 30°C, only faintly alters odor elicited calcium signals. This result opens the possibility to measure odorant representations with and without the contribution of the LNs in the same animal.