The physiology of olfactory neurons
One of my past research efforts focused on the physiological properties of human olfactory receptor neurons (see references below). Specifically, I looked at the cellular signaling processes involved individual olfactory neurons’ response to odorants stimulation. I adopted these techniques for the study of olfaction in birds.
Pseudocolor image of an olfactory receptor neuron loaded with the fluorescent dye fura-2. Left panels, pseudocolored images of an olfactory neuron at 340 and 360 nm excitation. Right top panel shows a pseudocolor representation of the ratio between the pixel intensities of the 340 and 360 image, multiplied by a calibration factor to obtain the calcium concentration. Red represents high calcium, and blue represents low calcium. Right bottom panel shows a photomicrograph of the cell.
Birds represent a unique model for study because they represent a unique group, evolutionarily related to reptiles but physiologically similar to mammals (endothermic). Their olfactory system appears simple, with a single coiled turbinate. Although olfaction in birds is generally thought to be of minor importance, many behavioral studies have demonstrated the importance of olfaction in bird feeding and social behavior.
I currently use calcium imaging techniques to measure changes in intracellular calcium in single cells because olfactory neurons respond to odorants with changes in intracellular calcium. In addition, this technique is relatively non-invasive (to the cells) and can be used to measure from a large number of cells from one specimen.
Left: the dissected olfactory cavity of a bird, showing a single coiled turbinate. Right: an isolated olfactory neuron from a chick. The black arrow points to the cilia and the dendrite; the white arrow points to the cell body. The axon is excised in the preparation and is thus not visible.
