Recent experimental and theoretical studies indicate that slow brain rhythms are generated by simple inhibitory neural networks. Sequential switching of tonic spiking activity is a widespread phenomenon underlying such rhythms. In this paper, we analyze a minimal, reciprocally connected circuit of three spiking units in the cases of different excitability classes of models. It is shown that in both types arising of stable heteroclic contour produces sequentail activation and slow rhythm generation in neural microcircuit. Bifurcation of heteroclinic contour arising is investigated.
