EFFECTS OF NONPEPTIDE V_1a AND V₂ ANTAGONISTS ON BLOOD PRESSURE FAST OSCILLATIONS IN CONSCIOUS RATS

Abstract

This paper describes the effects of vasopressin nonpeptide selective V_1a (OPC-21268) and V₂ (OPC-31260) antagonists on fast blood pressure (BP) oscillations in conscious non-haemorrhaged and haemorrhaged rats. Equidistant sampling at 20 Hz allowed direct spectral analysis of BP on 30 overlapping 2048 point-time series. In non-haemorrhaged rats, V_1a antagonist (5 mg/kg; i.v) reduced BP and low-frequency (LF-BP) component while subsequent administration of V₂ antagonist (1 mg/kg; i.v) reversed these changes and enhanced the very low-frequency (VLF-BP) component. In haemorrhaged rats (5-15 ml/kg/min) V₂ antagonist pre-treatment enhanced the VLF-BP component during normotensive bleeding, while the V_1a antagonist pre-treatment modified BP variability after hypotensive haemorrhage by enhancing the HF-SBP component. The results suggest that under normotensive conditions vasopressin by the stimulation of both V_1a and V₂ receptors buffers BP variability in the VLF-BP frequency domain. In addition, under hypotensive conditions vasopressin, by the stimulation of V_1a receptors buffers the respiration-induced HF-BP oscillation.

• Spectral analysis
• Haemorrhage
• Heart rate
• Blood pressure
• Vasopressin