Nicotine-induced dendritic remodeling in the insular cortex

The insular cortex has emerged as a novel target for nicotine addiction research. One unresolved question about the insular cortex is whether its neurons exhibit nicotine-induced dendritic remodeling similar to other brain regions implicated in nicotine addiction. To test this question, Long–Evans rats were administered nicotine via osmotic pump for two weeks. Thirty-seven days following the end of nicotine dosing, rats were sacrificed for Golgi-Cox staining and pyramidal neurons from the rostral agranular insular cortex were digitally reconstructed in three dimensions. Results from morphometric analyses revealed an increased complexity of dendrites in the insular cortex following nicotine. Increases were found for both total dendrite length and number of bifurcations. Sholl analyses revealed these changes depended on the distance from the soma, with the most prominent changes distributed at distal points along the dendritic tree. A follow-up comparison of length and bifurcation measurements from Sholl analyses suggested that new dendritic branches, rather than growth of existing dendrites, most likely contributed to overall changes in complexity. No change in dendrite morphology was found for apical dendrites. Together, these results show the insular cortex is a target for neuroplasticity following nicotine exposure.