Computational model of carbachol-induced delta, theta and gamma-like oscillations in hippocampus

Application of carbachol (cch) can induce oscillations in the (cch-,0.5 }2 Hz), (cch-, 4}12 Hz),and (cch-,30 }80 Hz) frequency-range in the rat hippocampal slice preparation. Using model CA3 cells we found that the time scale for cch- was determined by the decay constant of I - ,that of cch- by an intrinsic subthreshold membrane potential oscillation, and that of cch- by the decay constant of GABA-ergic postsynaptic potentials. The known physiological e!ects of carbachol on I and I - ,and on the strength of excitatory postsynaptic potentials produced the observed transitions from incoherent cch- to cch-,and from cchto cch- with increasing cch concentrations,as well as the nested cch- - and cch-- seen in experiment. 2001 Elsevier Science B.V. All rights reserved.