Dopaminergic inhibition of excitatory inputs onto pyramidal tract neurons in cat motor cortex

The role of dopamine (DA) on motor cortical pyramidal tract neurons (PTNs) was studied in anesthetized cats with in vivo extracellular recordings in r esponse to transcallosal (TC) and ventrolateral (VL) thalamic stimulations. An antidromic PT potential was evoked to recognize PTNs. In most PTNs, ion tophoretic application of DA significantly reduced the spike activity exert ed by 20 single-pulse stimulations. Both D-1-like and D-2-like receptor ant agonists blocked (disinhibited) the effect in a similar way regardless of T C and VL stimulations, suggesting colocalization of two receptors, Except f or the presence of littering, the mean latency was usually fixed and short. These findings indicate that ventral midbrain DA imposes an intense suppre ssion in modulating PTNs response to both callosal and thalamocortical exci tatory inputs in motor cortex. Such DAergic suppression could play pivotal role to improve motor and sensorimotor signal integration. (C) 2001 Elsevie r Science Ireland Ltd. All rights reserved.