Application of OT and AVP led to a depolarization and an increased activity in supraoptic neurons. a, Example of a neuron (P9) responding to OT application (100 nm) by a sustained depolarization and a tonic activity. AVP had no effect in this neuron. b, Application of AVP (100 nm) on another neuron (P12) that was insensitive to OT led to a sustained depolarization and a phasic activity. These neurons have been slightly hyperpolarized before application of agonists to suppress the spontaneous activity.