Adult-born neurons (ABNs) are added to the olfactory bulb (OB) throughout life in rodents. While many factors have been identified as regulating the survival and integration of ABNs into existing circuitry, the understanding of how these factors affect ABN morphology and connectivity is limited. Here we compare how cell intrinsic [small interfering RNA (siRNA) knock-down of voltage gated sodium channels NaV1.1–1.3] and circuit level (naris occlusion) reductions in activity affect ABN morphology during integration into the OB. We found that both manipulations reduce the number of dendritic spines (and thus likely the number of reciprocal synaptic connections) formed with the surrounding circuitry and inhibited dendritic ramification of ABNs. Further, we identified regions of ABN apical dendrites where the largest and most significant decreases occur following siRNA knock-down or naris occlusion. In siRNA knock-down cells, reduction of spines is observed in proximal regions of the apical dendrite. This suggests that distal regions of the dendrite may remain active independent of NaV1.1–1.3 channel expression, perhaps facilitated by activation of T-type calcium channels and NMDA receptors. By contrast, circuit level reduction of activity by naris occlusion resulted in a global depression of spine number. Together, these results indicate that ABNs retain the ability to develop their typical overall morphological features regardless of experienced activity, and activity modulates the number and location of formed connections.
Keywords: neurogenesis, morphology, activity, olfaction, naris occlusion, sodium channels
Citation: Dahlen JE, Jimenez DA, Gerkin RC and Urban NN (2011) Morphological analysis of activity-reduced adult-born neurons in the mouse olfactory bulb. Front. Neurosci. 5:66. doi: 10.3389/fnins.2011.00066
Received: 06 December 2010; Paper pending published: 17 January 2011;
Accepted: 27 April 2011; Published online: 09 May 2011.
Edited by:Jack M. Parent, University of Michigan, USA
Reviewed by:Luca Bonfanti, University of Turin, Italy
Copyright: © 2011 Dahlen, Jimenez, Gerkin and Urban. This is an open-access article subject to a non-exclusive license between the authors and Frontiers Media SA, which permits use, distribution and reproduction in other forums, provided the original authors and source are credited and other Frontiers conditions are complied with.
*Correspondence: Nathan N. Urban, Department of Biological Sciences, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA. e-mail: firstname.lastname@example.org