SPLTRAK Abstract Submission
Cell Identity, Membrane Properties, and Spiking Profile of Rat Olfactory Bulb Dopamine Neurons
Kirill S. Korshunov1, 2, Laura J. Blakemore1, Richard Bertram1, 3, Paul Q. Trombley1, 2
1Program in Neuroscience, Florida State University, Tallahassee, FL, United States
2Department of Biological Science, Florida State University, Tallahassee, FL, United States
3Department of Mathematics, Florida State University, Tallahassee, FL, United States

Dopamine (DA) neurons of the olfactory bulb (OB), located in the glomerular layer (GL), are known to contribute to synaptic gating of odor signals and to odor sensitivity. However, their neuronal identity is controversial and their spiking profile has not been fully described. To further characterize these neurons, we used a transgenic rat model (hTH-GFP) in which DA neurons fluoresce. The processes of these neurons vary in length, possibly indicative of two cell types with intra- and interglomerular projections. Using whole-cell electrophysiology, we determined membrane properties of OB DA neurons, which differed between large and small neurons but not between their superficial and deep localization in the GL. Thus, large and small OB DA neurons may be of two cell types. We also determined that OB DA neurons do not fire spontaneously and produce a single spike in response to depolarizing stimuli. This single spiking is likely a direct result of the Na+ currents, as Na+ channels in these neurons quickly inactivate following depolarization and require a long duration to reactivate. A-type K+ and h-currents, also present in these neurons, likely do not directly contribute to this activity. Lastly, their spiking was further examined with different current slopes (ramp stimuli). Steep ramp stimuli produced fewer spikes with higher spike frequency and a larger tonic firing range (the amount of current at which these neurons could spike). Conversely, shallow stimuli produced more spikes with lower spike frequency and a smaller tonic firing range. Given these data, these neurons may be gated by a low-pass filter and may fire more when activated by small stimuli. Given their inhibitory nature, OB DA neurons may be more responsive to, and more likely to filter out, weaker, more tonic odor signals.