Vasoactive intestinal peptide (VIP) is expressed in a subset of cortical

GABAergic neurons that are derived from the caudal ganglionic eminence (CGE) and do not overlap with SST or PV interneurons (Miyoshi et al., 2010). A prominent feature of some VIP interneurons is their preferential innervation of other inhibitory interneurons (Dávid et al., 2007 and Somogyi et al., 2003). VIP Vemurafenib ic50 neurons may also regulate cortical blood flow and metabolism since its receptors appear to localize to blood vessels as well as neurons (Cauli and Hamel, 2010). In the VIP-ires-Cre driver, Cre activity is detected in the neocortex, hippocampus, olfactory bulb, suprachiasmatic nuclei, and other discrete midbrain and brainstem regions ( Figure S5). In the upper layers of barrel cortex, the fraction of GFP neurons that showed VIP immunofluorescence was 91.5% and the fraction of VIP+ cells expressing GFP was 84.5%

(n = 213 cells). Most VIP neurons in layer 2/3 typically extend vertically oriented dendrites ( Figures 7A and 7B and Movie S2). In contrast to SST interneurons ( Figure 5A), VIP neurons do not elaborate significant axon arbors in layer1 ( Figures 7A and 7B). In hippocampal CA1, VIP neuron axons appear as two distinct bands in stratum pyramidale and stratum orien CX-5461 datasheet ( Figure 7A). Using visual cortical slices from VIP-ires-Cre;Ai9, SST-ires-Cre;Ai9, and PV-ires-Cre;Ai9 mice, we compared the intrinsic properties of all VIP, SST, and PV interneurons. Consistent with prior studies on the corresponding neurons in the rat ( Cauli et al., 2000), VIP cells showed the largest input resistance, broadest action potentials, and exhibited firing patterns with the most accommodation and the lowest maximal frequency among the

three cell populations ( Figure 7F). VIP expression, like SST, begins during the neonatal period, and thus the VIP-ires-Cre driver can be used to visualize and manipulate developing VIP interneurons. At P0, we found that VIP neurons migrate in the white matter and begin to enter the cortical plate (data not shown). At P2, many VIP neurons have entered the cortex and appeared to strictly migrate radially toward the pia. During this period, they display strikingly homogenous morphology with vertically oriented leading neurites toward the pia and a long trailing process toward the white matter ( Figure 7D). These observations suggest that after reaching the cortex, VIP neurons largely disperse within the intermediate zone and attain their laminar positions by radial migration from IZ into the cortex. Such a highly homogeneous mode of migration is in sharp contrast to SST neurons, which enter the cortex in both marginal and intermediate zone and migrate in multiple modes and directions to reach their laminar positions ( Figures 5H and 5I).