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Innervation of interneurons immunoreactive for VIP by intrinsically bursting pyramidal cells and fast‐spiking interneurons in infragranular layers of juvenile rat neocortex
Author(s) -
Staiger Jochen F.,
Schubert Dirk,
Zuschratter Werner,
Kötter Rolf,
Luhmann Heiko J.
Publication year - 2002
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1046/j.1460-9568.2002.02048.x
Subject(s) - bursting , biocytin , neocortex , neuroscience , pyramidal cell , interneuron , vasoactive intestinal peptide , somatosensory system , axon , inhibitory postsynaptic potential , barrel cortex , biology , chemistry , electrophysiology , biophysics , hippocampus , receptor , neuropeptide , biochemistry
Cortical columns contain specific neuronal populations with characteristic sets of connections. This wiring forms the structural basis of dynamic information processing. However, at the single‐cell level little is known about specific connectivity patterns. We performed experiments in infragranular layers (V and VI) of rat somatosensory cortex, to clarify further the input patterns of inhibitory interneurons immunoreactive (ir) for vasoactive intestinal polypeptide (VIP). Neurons in acute slices were electrophysiologically characterized using whole‐cell recordings and filled with biocytin. This allowed us to determine their firing pattern as regular‐spiking, intrinsically bursting and fast‐spiking, respectively. Biocytin was revealed histochemically and VIP immunohistochemically. Sections were examined for contacts between the axons of the filled neurons and the VIP‐ir targets. Twenty pyramidal cells and five nonpyramidal (inter)neurons were recovered and sufficiently stained for further analysis. Regular‐spiking pyramidal cells displayed no axonal boutons in contact with VIP‐ir targets. In contrast, intrinsically bursting layer V pyramidal cells showed four putative single contacts with a proximal dendrite of VIP neurons. Fast‐spiking interneurons formed contacts with two to six VIP neurons, preferentially at their somata. Single as well as multiple contacts on individual target cells were found. Electron microscopic examinations showed that light‐microscopically determined contacts represent sites of synaptic interactions. Our results suggest that, within infragranular local cortical circuits, (i) fast‐spiking interneurons are more likely to influence VIP cells than are pyramidal cells and (ii) pyramidal cell input probably needs to be highly convergent to fire VIP target cells.