Diagonal band of Broca (DBB) neurons projecting to the hypothalamic supraoptic neurosecretory neurons were antidromically identified in pentobarbital-anesthetized male Long-Evans rats. Six of 12 DBB neurons tested for response to baroreceptor activation showed a consistent increase in firing. We propose that the established baroreceptor-induced inhibition of hypothalamic vasopressinergic neurons is mediated through DBB neurons.