Nociceptin/orphanin FQ modulates the cardiovascular, but not renal, responses to stress in spontaneously hypertensive rats

1. The central administration of the endogenous opioid-like peptide nociceptin/orphanin FQ (N/OFQ) produces marked cardiovascular depressor and renal sympathoinhibitory responses in conscious animals. These findings are evidence that central N/OFQ may modulate the cardiovascular and renal responses to acute environmental stress. 2. The changes in cardiovascular and renal function produced by intracerebroventricular (i.c.v.) N/OFQ were measured in conscious spontaneously hypertensive rats (SHR) under basal conditions and during the acute environmental stimulus of air jet stress. 3. In SHR, central N/OFQ produced profound hypotensive, bradycardic, renal sympathoinhibitory (delayed) and water-diuretic effects by a pathway that does not involve activation of central alpha2-adrenoceptors or classical opioid receptors. 4. Intracerebroventricular injection of N/OFQ prevented the pressor response and blunted the tachycardia to air jet stress. A similar renal sympathoexcitatory and antinatriuretic response was observed in conscious SHR during air stress, before and after i.c.v. N/OFQ. 5. These findings are evidence that, in conscious SHR, i.c.v. N/OFQ selectively inhibited the neural responses to air jet stress by attenuating sympathetic outflow to the heart and, potentially, vasculature, but not to the kidneys. Central endogenous N/OFQ systems may be activated and contribute to regional changes in sympathetic outflow during acute stress.