Neuroligin 1 (NLGN1) belongs to the type-B carboxylesterase/lipase family, is a synaptic cell-adhesion molecule that is enriched in postsynaptic densities where it may recruit receptors, channels, and signal-transduction molecules to synaptic sites of cell adhesion. Neuroligins consists of five members (NLGN1, NLGN2, NLGN3, NLGN4, and NLGN4Y), which interact with beta-neurexins, and this interaction is involved in the formation of functional synapses. The extracellular domain of functional Neuroligin 1 associates as a dimer when analyzed by sedimentation equilibrium. Neuroligin 1 has a unique N-linked glycosylation pattern in the neuroligin family, and glycosylation and its processing modify neuroligin activity. Neuroligin 1 is a potent trigger for the de novo formation of synaptic connections, and it has recently been suggested that it is required for the maturation of functionally competent excitatory synapses. The persistent expression of Neuroligin 1 is required for the maintenance of NMDAR-mediated synaptic transmission, which enables the normal development of synaptic plasticity and long-term memory in the amygdala of adult animals.