Neuropeptides and GABA are co-expressed and co-released by hippocampal interneurons. Bistratified and O-LM cells innervate segregated dendritic domains of pyramidal cells and co-release GABA and somatostatin acting on pre- and postsynaptic receptors. How do the activity patterns of these peptidergic/GABAergic interneurons support behaviour? Katona et al. recorded, labelled and identified individual interneurons in freely-moving rats and investigated their firing activity during movement and sleep in relation to hippocampal network oscillations. They found that behavioural and network states differentiate the firing of somatostatin-expressing bistratified and O-LM interneurons in the hippocampus. During movement, the two cell types cooperate temporally, firing at the trough of theta oscillatory cycles but at different frequencies. In contrast, during sleep, the two cell types dissociate in their function; bistratified cells are strongly active while O-LM cells decrease firing.
The results suggest that segregated glutamatergic inputs to CA1 pyramidal cell dendrites from the entorhinal cortex and the CA3 area are differentially modulated by GABA and somatostatin during behaviour.
At the 8th FENS forum of neuroscience held in Barcelona, aside from The Brain Prize 2011 lecture given by Peter Somogyi, the laboratory presented three posters which were all well attended.
Damien Lapray and his collaborators at Oxford and Vienna explored how the firing rate and patterns of GABAergic interneurons is adjusted in the neuronal network to ongoing behaviour in freely moving rats. They used novel innovative technology to record and label single GABAergic neurons while the rat moved, slept or just kept quiet in a small arena. Recorded parvalbumin–expressing basket interneurons innervate somata and proximal pyramidal cell dendrites, whereas nitric–oxide–synthase– and neuropeptide–Y–expressing ivy cells provide synaptic and extrasynaptic dendritic modulation.