Cardiovascular effects of injection of argipressin into lateral septal nuclei in rats

AIM

To determine whether argipressin (Arg) plays a role in central neural control of cardiovascular function by acting on the lateral septal nuclei (LSN).

METHODS

Measuring mean arterial blood pressure (MAP) and heart rate (HR) responses followed microinjection of Arg into the LSN of rats anesthetized with urethane.

RESULTS

Arg (100, 200, and 400 ng) injected into the LSN produced a dose-dependent hypertension and tachycardia. Maximal changes of MAP were 0.9 +/- 0.6, 2.3 +/- 1.3, 4.0 +/- 1.4 kPa, respectively; maximal changes of HR were 12 +/- 27, 50 +/- 33, and 89 +/- 27 bpm, respectively. Pretreatment of the LSN with a vasopressin 1 type antagonist d (CH2)5Tyr(Me) Arg abolished the MAP and HR responses produced by injection of Arg. Peripheral alpha-adrenergic blockade with phentolamine blocked the hypertension responses to injection of Arg into the LSN.

CONCLUSION

Arg acts in the region of the LSN to exert a central action on the cardiovascular system that is mediates by stimulation of sympathetic outflow.

Effects of argipressin injected into medial amygdaloid body on blood pressure and heart rate in rats

Graded injections of argipressin (Arg, 150, 300, and 600 ng/1.5 microliters CSF, 2 min) into the medial amygdaloid body in anesthetized rats produced a dose-related increase in the mean arterial pressure and heart rate (Maximal delta MAP = 2.9 +/- 1.5 kPa, Maximal delta HR = 67 +/- 38 bpm), which lasting > 40 min at 600 ng dosage. Naloxone (15 micrograms/15 microliters CSF) injected into the lateral ventricle blocked the cardiovascular responses to Arg. These results suggest that Arg exerts a central action on the cardiovascular system via the opioid in the lateral ventricle.