BACKGROUND AND PURPOSE Intracerebroventricularly injected tachykinin NK3 receptor (R) antagonists normalize mean arterial blood pressure (MAP) in spontaneously hypertensive rats (SHR). This study was pursued to define the role played by NK3R located on dopamine neurones of the ventral tegmental area (VTA) in the regulation of MAP in SHR.
EXPERIMENTAL APPROACH SHR (16 weeks) were implanted permanently with i.c.v. and/or VTA guide cannulae. Experiments were conducted 24 h after catheterization of the abdominal aorta to measure MAP and heart rate (HR) in freely behaving rats. Cardiovascular responses to i.c.v. or VTA‐injected NK3R agonist (senktide) and antagonists (SB222200 and R‐820) were measured before and after systemic administration of selective antagonists for D1R (SCH23390), D2R (raclopride) or non‐selective D2R (haloperidol), and after destruction of the VTA with ibotenic acid.
KEY RESULTS I.c.v. or VTA‐injected SB222200 and R‐820 (500 pmol) evoked anti‐hypertension, which was blocked by raclopride. Senktide (10, 25, 65 and 100 pmol) elicited greater increases of MAP and HR when injected in the VTA, and the cardiovascular response was blocked by R‐820, SCH23390 and haloperidol. VTA‐injected SB222200 prevented the pressor response to i.c.v. senktide, and vice versa, i.c.v. senktide prevented the anti‐hypertension to VTA SB222200. Destruction of the VTA prevented the pressor response to i.c.v. senktide and the anti‐hypertension to i.c.v. R‐820.
CONCLUSIONS AND IMPLICATIONS The NK3R in the VTA is implicated in the maintenance of hypertension by increasing midbrain dopaminergic transmission in SHR. Hence, this receptor may represent a therapeutic target in the treatment of hypertension.