Which neurotransmitter is primarily responsible for the generation of behaviors observed during dowsing?

The neurotransmitter is the Acetycholine.

The statement above describes the response as characterized by movements of the skeletal muscle (writing, dowsing), which is primarily carried out by the actions of acetylcholine released at the neuromuscular junction. Acetylcholine is a small molecule excitatory neurotransmitter with a wide variety of functions. In the sympathetic and parasympathetic nervous systems and at all neuromuscular junctions, ACh is used to signal muscle movement.