Information transfer between nerve cells and their targets is by chemical transmission at specialized contacts termed synapses. The main research interest of our group concerns the molecular components of the synaptic contacts, their structural organization, their roles in synaptic signaling, and the mechanisms of their regulation under physiological conditions and under pathological conditions, such as disease or injury. Much of our research has focused on the cholinergic system, which plays a major role in both the peripheral and the central nervous system of vertebrates. Acetylcholine (ACh) is the sole neurotransmitter at the neuromuscular junction (NMJ), has an important function in the autonomic nervous system and the spinal cord, and in the brain it is involved in such processes as cognition and memory. Binding of released ACh to its receptors (AChRs) in the postsynaptic membrane triggers a postsynaptic potential, and acetylcholinesterase (AChE), situated in the synaptic cleft, hydrolyzes ACh and terminates transmission. Our studies address specific issues concerning AChR and AChE: Regulation of these cholinergic components in the mature functional synapse, during development and in neuromuscular diseases, such as myasthenia and dystrophy; Structural organization of the components in peripheral and central cholinergic synapses, and their roles in synaptic signaling; The role of the cholinergic system in the spinal cord in the sensory activation of the mammalian motor system; and, Cholinesterases in cholinergic synapses and other systems, where they may play cholinergic or non-cholinergic functions.