Excitatory neurons experience structural remodeling under different conditions, involving changes in the length and complexity of dendritic arbors and the density or morphology of their spines (Fu and Zuo, 2011). By contrast, studies focused on interneuronal dendrites and spines are still scarce and we do not have many information on whether their synaptic inputs are similar to those found contacting the spines of excitatory neurons or whether the structural dynamics of interneurons is similar to that found in pyramidal cells. Only some recent studies have shown that inhibitory neurons undergo dendritic remodeling during normal conditions (Chen et al., 2011a) and after visual deprivation (Chen et al., 2011b). Our laboratory has also demonstrated that interneurons of the lateral and basolateral amygdala undergo dendritic atrophy after chronic stress (Gilabert-Juan et al., 2011). Although it has been classically considered that nearly all neocortical interneurons in the mature brain have aspiny dendrites (see Markram et al., 2004 for review), recent reports indicate that at least six different subtypes of interneurons in the adult mPFC form spines along their dendrites (Kawaguchi et al., 2006)(Kubota et al., 2011). Synaptic inputs to interneurons are made mainly onto the dendritic shaft. The dendritic shaft is structurally stable, but spines are frequently coming out and disappearing (Trachtenberg et al., 2002; Keck et al., 2011). Synapse formation by spine protrusion is considered to select specific axons among the many presynaptic axon candidates (Kubota et al., 2011). Only a recent study has described that a subpopulation of interneurons in the visual cortex expressing VIP display dendritic spines, which receive mainly a glutamatergic input, and that their density and turnover rate are dynamic (Keck et al., 2011). In this line, is particularly interesting to note that the presence of PSA-NCAM influences the dendritic spine density in interneurons (Gomez-Climent et al., 2011).

REAL-TIME MULTIPHOTON MICROSCOPY USING CRANIAL WINDOWS