Adenosinic modulation of 7-14 Hz spindle rhythms in interconnected thalamic relay and nucleus reticularis neurons.

Intrathalamic spindle rhythms have been shown in vitro and in vivo to recur at frequencies of 0.1-0.3 Hz and last for periods of 1-3 s depending on the species observed. Although it is now generally agreed that both the intrinsic properties of relay and reticularis neurons, as well as their circuit dependency, contribute to the 7-14 Hz interburst spindle frequency, it is not presently known what mechanisms generate these slower oscillations. A model of interconnected thalamocortical relay and nucleus reticularis thalami cells was developed to investigate these properties. The model suggests that modulation of the hyperpolarization-activated cation current, Ib, by the nucleoside adenosine can serve to regulate both the duration of spindling and frequency of recurrence. These results suggest that the waxing and waning characteristics of thalamic spindle rhythms are, in part, dependent on the changing levels of extracellular adenosine and its influence on Ib in thalamocortical relay cells within this neuronal network.