Blood pressure is controlled by endocrine, autonomic, and behavioral responses that maintain blood volume and perfusion pressure at levels optimal for survival. Although it is clear that central angiotensin type-1a receptors (AT1aR) influence these processes, the neuronal circuits mediating these effects are incompletely understood. The present studies characterize the structure and function of AT1aR neurons in the lamina terminalis (containing the median preoptic nucleus and organum vasculosum of the lamina terminalis), thereby evaluating their roles in blood pressure control. Using male AT1aR-Cre mice, neuroanatomical studies reveal that AT1aR neurons in the area are largely glutamatergic and send projections to the paraventricular nucleus of the hypothalamus (PVN) that appear to synapse onto vasopressin-synthesizing neurons. To evaluate the functionality of these lamina terminalis AT1aR neurons, we virally-delivered light-sensitive opsins and then optogenetically excited or inhibited the neurons while e...