A novel mechanism for short-term post-tetanic plasticity in thalamocortical neurons

Information transfer through the thalamus is a dynamic process, which can be influenced by multiple factors within the thalamocortical circuit. Activity-dependent changes in neuronal excitability and synaptic efficacy can impact both short- and long-term processing through the thalamocortical circuit. In these experiments, we investigate the mechanism of a novel form of post-tetanic synaptic plasticity, induced by tetanic stimulation of excitatory afferents onto thalamocortical neurons. We show that tetanic activation of excitatory afferents produces a short-lasting (10-15 min) facilitation of excitatory postsynaptic currents in ventrobasal thalamocortical neurons. This potentiation is mediated by a calcium-dependent, presynaptic mechanism. This potentiation is partly due to the activation of adenylyl cyclase and involves alteration in the hyperpolarization-activated mixed cation current, I_h. This activity-dependent facilitation of excitatory synaptic transmission provides a mechanism through which prolonged excitatory enhancement may impact sensory processing through thalamocortical circuits.