Synaptic Bombardment Modulates Muscarinic Effects in Forelimb Motor Cortex

Niraj S. Desai and Elisabeth C. Walcott

Continuous synaptic bombardment with a complex barrage of excitatory and inhibitory inputs alter many aspects of neuronal responsiveness (by depolarizing neurons, increasing membrane conductance, and introducing fluctuations). This study shows how it shapes neuromodulation of postsynaptic responses by examining muscarinic modulation of forelimb motor cortex, a brain area in which cholinergic stimulation is known to be necessary for modifications during motor skill learning. Using a dynamic clamp system to inject simulated conductances
into pyramidal neurons, they mimicked in vivo-like activity by introducing a random background of excitatory and
inhibitory inputs. The presence of such background conductances strongly attenuated most muscarinic neuromodulatory effects, with the notable exception that sustained firing responses to trains of inputs were well preserved. This may be important for promoting plasticity in vivo.

The Journal of Neuroscience, February 22, 2006 • 26(8):2215–2226


Similar thing may be happening in the slug's CPG in the sea water. Most of my experiments testing neuromodulation have been done in HiDi saline, which suppresses anonymous synaptic bombardment.