Comparison of the effects of 2‐deoxyglucose and immobilization on secretion and synthesis rate of catecholamines in the adrenal gland: a microdialysis study in conscious rats

Abstract

Using microdialysis, extracellular 3,4-dihydroxyphenylalanine (DOPA), noradrenaline (NA) and adrenaline (AD) concentrations in the adrenal gland were monitored in conscious rats during and after 60 min of immobilization (IMM) as well as after injection of 500 mg kg(-1) 2-deoxyglucose (2-DG). IMM produced a rapid and transient increase in secretion of AD (20-fold), NA (13-fold) and DOPA (3.6-fold). This was accompanied by an increase in blood pressure (+18 mmHG) and heart rate (+146 b.p.m.). Repeated exposure to IMM (daily 60 min, for 5 days) had no influence on either catecholamine secretion of haemodynamic profiles, indicating the lack of habituation to stressful conditions. Unlike IMM, the stress of 2-DG-induced central neuroglucopenia stimulated the release of AD without affecting NA secretion. AD levels peaked (5.1-fold increase) 40-60 min after 2-DG injection and then slowly declined. 2-DG induced no changes in blood pressure but reduced the heart rate (-48 b.p.m.). In separate experiments, steady-state dialysate DOPA levels, reached during continuous infusion of decarboxylase inhibitor NSD 1015 into adrenal gland tissue through the dialysis probe, served as an index of adrenomedullary tyrosine hydroxylase (TH) activity. IMM evoked a marked response in TH activity (DOPA formation increased 2.7-fold), which remained elevated 60 min after the cessation of stress when AD and NA secretion had already fallen to baseline. After 2-DG, despite significant hormonal response, adrenal TH activity was unchanged. These results give clear evidence that IMM and 2-DG-induced neuroglucopenia may be considered as two different types of stressful stimuli.

Chronic intermittent hypoxia induces hypoxia‐evoked catecholamine efflux in adult rat adrenal medulla via oxidative stress

“…4). As reported by others (Kuzmin et al 1995; Vollmer et al 1997; Morrison & Cao, 2000), we also found that 2‐DG had no significant effect on the NA content of normoxic and CIH adrenal medullae.…”

“…Since activation of nicotinic cholinergic receptors is critical for evoking neurally mediated CA secretion from the adrenal medulla, we hypothesized that CIH downregulates neurogenic mediation of CA secretion. To test this possibility, we assessed the effect of systemic administration of 2‐deoxyglucose (2‐DG), which selectively depletes ADR from the adrenal medulla by activating 2‐DG‐sensitive sympathetic fibres (Kuzmin et al 1995; Vollmer et al 1997; Morrison & Cao, 2000). In control rats, 2‐DG reduced adrenal ADR from 42 ± 0.5 to 9 ± 1.2 nmol per adrenal medulla (78% depletion; Fig.…”

Repeated 2-deoxy-D-glucose-induced glucoprivation attenuates Fos expression and glucoregulatory responses during subsequent glucoprivation.

“…Glucoprivation is a potent stimulus for adrenal medullary secretion, which could potentially alter cardiovascular function and lead to changes in Fos expression in these cardiovascular areas. However, expression of Fos in TH-ir neurons after 2DG administration is not secondary to changes in cardiovascular parameters induced by glucoprivation, since 2DG does not alter blood pressure (22). In addition, 2DG-induced expression of Fos in TH-ir neurons is not altered by adrenal denervation, which completely blocks adrenal medullary secretion (7).…”

Learning about stress: neural, endocrine and behavioral adaptations

“…elicited a relatively selective increase in dialysate levels of EPI, while levels of NE remained constant. EPI/NE peaked at approximately 10.0 one hour after injection of 2-deoxy-D-glucose (Kuzmin et al, 1995). In an earlier study that combined adrenal medullary microdialysis and measurement of circulating catecholamines, Kuzmin et al (1990) reported that plasma NE from the adrenal medulla of laboratory rats increased from 9% under basal conditions to 50% during hemorrhage.…”

“…Using microdialysis of the adrenal medulla of laboratory rats, Kuzmin et al (1995) studied the effects on catecholamine secretion of acute immobilization stress for 60 min. Adrenal medullary dialysate was collected before, during and after immobilization and later analyzed for content of NE and EPI.…”