Brain Region‐Specific Expression of Angiotensin AT1A Receptors in Microglia

Abstract

Through its actions at the AT1A receptor in the hypothalamus, the renin‐angiotensin system contributes to the control of resting metabolic rate and blood pressure. Activation of microglia is required for angiotensin‐dependent hypertension, and exposure to high fat diet increases microglia infiltration in the hypothalamus. We therefore hypothesized that angiotensin AT1A receptors are expressed on microglia within the hypothalamus, and that these cells may play a role in the development of obesity‐hypertension. Brains from mice expressing green fluorescent protein via the angiotensin AT1A promoter (“NZ44” mice from the GenSat Project) were sectioned and immunostained to label microglia via antibodies against allograft inflammatory factor 1 (IBA1) conjugated to red fluorescent protein. When mice were maintained on standard chow diet, we observed dual‐fluorescent cells within the ventromedial hypothalamus, but not in the arcuate nucleus, median eminence, paraventricular nucleus, dorsomedial hypothalamus, or subfornical organ despite substantial numbers of singly‐fluorescent cells in each of these regions. Together, these data support a region‐specific expression of AT1A in microglia. Ongoing studies are focused on investigating the effects of dietary interventions (e.g. – high fat diet) and hypertensive stimuli (e.g. – deoxycorticosterone acetate (DOCA)‐salt treatment) upon region‐specific microglial infiltration, activation, and expression of AT1A.