Challenge tests: Assessment of the noradrenergic and gaba systems in depression and anxiety disorders

Effect of sleep deprivation on the growth hormone response to the alpha-2 adrenergic receptor agonist, clonidine, in normal subjects

“…The failure of desipramine, a noradrenaline reuptake 296 S. Lal et al inhibitor, to enhance GH secretion after SD (Calil et al, 1987) may be related to its lack of selectivity. The increase in GH secretion following CLON may involve the release of GH-releasing factor (GRF) or inhibition of somatostatin release (Coupland et al, 1992). It is unlikely, however, that SD increases CLON-induced GH secretion by a direct effect on GRF or somatostatin secretion and independent of an adrenergic mechanism as SD itself does not increase GH secretion.…”

Neuropsychological performance and noradrenaline function in chronic fatigue syndrome under conditions of high arousal

“…High doses of clonidine (2.5 g/kg) are thought to have a facilitatory effect on noradrenaline function through post-synaptic actions at alpha-2 adrenoceptors, but low doses act pre-synaptically at alpha-2 adrenoceptors to inhibit noradrenaline function (Coupland et al 1992). Central alpha-2 adrenoceptor function can be explored through growth hormone and cortisol responses to clonidine challenge (Coupland et al 1992; Kovacs and Makara, 1993).…”

“…Central alpha-2 adrenoceptor function can be explored through growth hormone and cortisol responses to clonidine challenge (Coupland et al 1992; Kovacs and Makara, 1993). High doses of clonidine have mixed effects on objective neuropsychological performance in normal human volunteers; performance is improved on tests of working memory and visuo-spatial learning but there is greater impulsivity in planning and impaired sustained attention (Coull et al 1995a(Coull et al , 1995bMiddleton et al 1999).…”

Discriminating Depression, Physical and Social Anhedonia by Neurotransmitter Related Challenge Tests

“…review by Power & Cowen, 1992;Yatham & Steiner, 1993 for the serotonergic systems or review by Coupland et al, 1992 for the noradrenergic system, and by Insel & Sievers, 1981 for the dopaminergic system). Depressed patients, for instance, have been reported to show blunted hormone responses to the 5-hydroxy-tryptamine (5-HT) releaser d-fenfluramine (Cleare et al, 1996), the 5-HT-reuptake inhibitors citalopram (Mattos et al, 2006), or clomipramin (Anderson et al, 1992), as well as increased hormone responses to stimulation of the noradrenertgic system (NA), e.g., by the alpha2 receptor agonist clonidine (Charney et al, 1982;Lesch et al, 1988) or the noradrenaline reuptake inhibitor reboxetine (Schüle et al, 2004).…”