Z. Nusser et al., Disruption of GABA(A) receptors on GABAergic interneurons leads to increased oscillatory power in the olfactory bulb network, J NEUROPHYS, 86(6), 2001, pp. 2823-2833
Synchronized neural activity is believed to be essential for many CNS funct
ions, including neuronal development, sensory perception, and memory format
ion. In several brain areas GABA(A) receptor-mediated synaptic inhibition i
s thought to be important for the generation of synchronous network activit
y. We have used GABA(A) receptor beta3 subunit deficient mice (beta3-/-) to
study the role of GABAergic inhibition in the generation of network oscill
ations in the olfactory bulb (OB) and to reveal the role of such oscillatio
ns in olfaction. The expression of functional GABA(A) receptors was drastic
ally reduced (>93%) in beta3-/- granule cells, the local inhibitory interne
urons of the OB. This was revealed by a large reduction of muscimol-evoked
whole-cell current and the total current mediated by spontaneous, miniature
inhibitory postsynaptic currents (mIPSCs). In beta3-/- mitral/tufted cells
(principal cells), there was a two-fold increase in mIPSC amplitudes witho
ut any significant change in their kinetics or frequency. In parallel with
the altered inhibition, there was a significant increase in the amplitude o
f theta (80% increase) and gamma (178% increase) frequency oscillations in
beta3-/- OBs recorded in vivo from freely moving mice. In odor discriminati
on tests, we found beta3-/- mice to be initially the same as, but better wi
th experience than beta3+/+ mice in distinguishing closely related monomole
cular alcohols. However, beta3-/- mice were initially better and then worse
with practice than control mice in distinguishing closely related mixtures
of alcohols. Our results indicate that the disruption of GABA(A) receptor-
mediated synaptic inhibition of GABAergic interneurons and the augmentation
of IPSCs in principal cells result in increased network oscillations in th
e OB with complex effects on olfactory discrimination, which can be explain
ed by an increase in the size or effective power of oscillating neural cell
assemblies among the mitral cells of beta3-/- mice.