Af. Martindelcampo et al., HIGH-DOSE NALOXONE (1.0 MG KG) - PSYCHOLOGICAL AND ENDOCRINE EFFECTS IN NORMAL-MALE SUBJECTS PRETREATED WITH ONE MILLIGRAM OF DEXAMETHASONE/, Psychoneuroendocrinology, 23(4), 1998, pp. 413-424
The possible participation of the endogenous opioid system (EOS) in th
e negative feedback of the hypothalamic-pituirary-adrenal axis (HPA-a)
activated by low doses (1 mg) of dexamethasone (Dex) was investigated
. Ten male healthy subjects (mean age 31.5 +/- 1.9 SEM) were studied o
n 2 separate days, in a double-blind, cross-over and placebo-controlle
d design. All subjects were pretreated with 1.0 mg Dex orally the nigh
t (2300h) before both test days. On the study days, subjects were admi
tted at 0700h for cannula insertion; the administration of an IV bolus
of either naloxone (Nal) (1.0 mg/kg) or saline solution (Sal) IV was
started at 0900h. Before and following each infusion, mood was measure
d by a Visual Analogue Scales (VAS) and by the Affective Quality Scale
(AQS) every 30 min and blood samples were taken at 15-min intervals.
Blood pressure and heart rate were also monitored. Before Dex administ
ration, plasma cortisol levels were within the normal range in all sub
jects (210.4 +/- 13 ng/ml), while after 9 h after Dex cortisol levels
showed the expected significant (p < 0.01) decrease (11.5 +/- 1.9 and
15.04 +/- 0.7 ng/ml for Sal and Nal test days respectively). There wer
e no detectable increases in plasma cortisol levels following either N
al nor Sal administration. However, there was a Nal-induced significan
t increase in LH (p < 0.01) thus indicating that an effective opioid b
lockade at the level of the hypothalamic-pituitary unit occurred. Ther
e were also a mild and selective Dex + Nal-induced dysphoric (mood fac
tors related to subjects perception of their cognition) and bradycardi
c effects (p < 0.05). These results suggest that the EOS is not direct
ly involved in the negative feedback triggered by low doses of Dex of
the HPA-a, and that there might be a possible glucocorticoid-opioid in
teraction for the modulation of some aspects of mood. (C) 1998 Elsevie
r Science Ltd. All rights reserved.