Plasma nociceptin/orphanin FQ levels in response to the hyperventilation test in healthy subjects

Abstract In vitro and in vivo studies demonstrated that nociceptin/orphanin FQ inhibits norepinephrine release, while the effects of norepinephrine on nociceptin/orphanin FQ release remain unknown. Previous studies in healthy and hypertensive subjects showed that prolonged and forced hyperventilation induces different blood pressure (BP) responses depending on changes in plasma catecholamine levels. We investigated whether the effects of hyperventilation on the sympatho-adrenergic system involve nociceptin/orphanin FQ release. Fifty-six healthy subjects (26 females, mean age 63 ± 2 and 30 males, mean age 63 ± 3) underwent the hyperventilation test. A hierarchical cluster analysis based on BP response to hyperventilation identified three groups of subjects: group 1 ( n  = 20) with a decrease in BP, norepinephrine (1311.1 ± 45.5 fmol/ml versus 900.0 ± 55.3 fmol/ml, P P n  = 18) without any change in BP and norepinephrine (1133.0 ± 31.5 fmol/ml versus 1176.0 ± 44.6 fmol/ml), with a decrease in nociceptin/orphanin FQ (12.5 ± 3.2 pg/ml versus 7.4 ± 0.6 pg/ml, P n  = 18) with an increase in BP, norepinephrine (1216.7 ± 50.9 fmol/ml versus 1666.7 ± 44.9 fmol/ml, P P P