Increased activity of pre-motor network does not change the excitability of motoneurons during protracted scratch initiation

Intrinsic response properties of neurons change during network activity. These changes may reinforce the initiation of particular forms of network activity. If so, the involvement of neurons in particular behaviours in multifunctional networks could be determined by up- or down-regulation of their intrinsic excitability. Here we employed an experimental paradigm of protracted scratch initiation in the integrated carapace–spinal cord preparation of adult turtles (Chrysemys scripta elegans). The protracted initiation of scratch network activity allows us to investigate the excitability of motoneurons and pre-motor network activity in the time interval from the start of sensory stimulation until the onset of scratch activity. Our results suggest that increased activity in the pre-motor network facilitates the onset of scratch episodes but does not change the excitability of motoneurons at the onset of scratching.