Differential effect of glucocorticoids on abdominal pain induced by morphine

Sphincter of Oddi dysfunction: is there a role for medical therapy?

If the mechanism of pain in patients with sphincter of Oddi (SO) dysfunction is functional obstruction of the biliary tract, and at least in some patients it results from sphincter smooth muscle hypertrophy, then smooth muscle relaxants should have a theoretic role in the management of these patients. Calcium channel antagonists and other smooth muscle relaxants have been shown in "acute" manometric studies to alter SO motility. However, the effect of these agents on vascular smooth muscle remains a concern and often limits their use. At present the role of medical therapy is somewhat unclear because few well-conducted studies have used manometric criteria for the diagnosis of SO dysfunction and the selection of patients for therapy. The main drawback is that no drugs appear to be specific for the SO, long acting, and free of side effects.

Effects of antecedent prolonged exercise on subsequent counterregulatory responses to hypoglycemia

In the present study the hypothesis tested was that prior exercise may blunt counterregulatory responses to subsequent hypoglycemia. Healthy subjects [15 females (f)/15 males (m), age 27 +/- 1 yr, body mass index 22 +/- 1 kg/m(2), hemoglobin A(Ic) 5.6 +/- 0.5%] were studied during 2-day experiments. Day 1 involved either 90-min morning and afternoon cycle exercise at 50% maximal O2 uptake (VO2(max)) (priorEXE, n = 16, 8 m/8 f) or equivalent rest periods (priorREST, n = 14, 7 m/7 f). Day 2 consisted of a 2-h hypoglycemic clamp in all subjects. Endogenous glucose production (EGP) was measured using [3-3H]glucose. Muscle sympathetic nerve activity (MSNA) was measured using microneurography. Day 2 insulin (87 +/- 6 microU/ml) and plasma glucose levels (54 +/- 2 mg/dl) were equivalent after priorEXE and priorREST. Significant blunting (P < 0.01) of day 2 norepinephrine (-30 +/- 4%), epinephrine (-37 +/- 6%), glucagon (-60 +/- 4%), growth hormone (-61 +/- 5%), pancreatic polypeptide (-47 +/- 4%), and MSNA (-90 +/- 8%) responses to hypoglycemia occurred after priorEXE vs. priorREST. EGP during day 2 hypoglycemia was also suppressed significantly (P < 0.01) after priorEXE compared with priorREST. In summary, two bouts of exercise (90 min at 50% VO2(max)) significantly reduced glucagon, catecholamines, growth hormone, pancreatic polypeptide, and EGP responses to subsequent hypoglycemia. We conclude that, in normal humans, antecedent prolonged moderate exercise blunts neuroendocrine and metabolic counterregulatory responses to subsequent hypoglycemia.

Opioid poorly-responsive cancer pain. Part 2: basic mechanisms that could shift dose response for analgesia

Basic research in experimental pain models may illuminate the phenomenon of cancer pain that is poorly responsive to opioid drugs. Research findings can be valuable in formulating new strategies in clinical practice. This review evaluated experimental observations in terms of the events that occur in cancer patients receiving opioid therapy for pain.

Role of cortisol in the pathogenesis of deficient counterregulation after antecedent hypoglycemia in normal humans

The aim of this study was to determine the role of increased plasma cortisol levels in the pathogenesis of hypoglycemia-associated autonomic failure. Experiments were carried out on 16 lean, healthy, overnight fasted male subjects. One group (n = 8) underwent two separate, 2-d randomized experiments separated by at least 2 mo. On day 1 insulin was infused at a rate of 1.5 mU/kg per min and 2 h clamped hypoglycemia (53 +/- 2 mg/dl) or euglycemia (93 +/- 3 mg/dl) was obtained during morning and afternoon. The next morning subjects underwent a 2-h hyperinsulinemic (1.5 mU/kg per min) hypoglycemic (53 +/- 2 mg/dl) clamp study. In the other group (n = 8), day 1 consisted of morning and afternoon 2-h clamped hyperinsulinemic euglycemia with cortisol infused to stimulate levels of plasma cortisol occurring during clamped hypoglycemia (53 mg/dl). The next morning (day 2) subjects underwent a 2-h hyperinsulinemic hypoglycemic clamp identical to the first group. Despite equivalent day 2 plasma glucose and insulin levels, steady state epinephrine, norepinephrine, pancreatic polypeptide, glucagon, ACTH and muscle sympathetic nerve activity (MSNA) values were significantly (R < 0.01) blunted after day 1 cortisol infusion compared to antecedent euglycemia. Compared to day 1 cortisol, antecedent hypoglycemia produced similar blunted day 2 responses of epinephrine, norepinephrine, pancreatic polypeptide and MSNA compared to day 1 cortisol. Antecedent hypoglycemia, however, produced a more pronounced blunting of plasma glucagon, ACTH, and hepatic glucose production compared to day 1 cortisol. We conclude that in healthy overnight fasted men (a) antecedent physiologic increases of plasma cortisol can significantly blunt epinephrine, norepinephrine, glucagon, and MSNA responses to subsequent hypoglycemia and (b) these data suggest that increased plasma cortisol is the mechanism responsible for antecedent hypoglycemia causing hypoglycemia associated autonomic failure.

Sympathoadrenal system in stress. Interaction with the hypothalamic-pituitary-adrenocortical system

Exposure of an organism to any of a variety of stressors markedly activates the sympathoadrenal and hypothalamic-pituitary-adrenocortical systems. Interactions of these major stress systems occur at several levels in the periphery and the brain. In the present study, we used sham-operated or adrenalectomized cortisol-treated conscious rats to examine glucocorticoid effects on indices of CA release, metabolism, and synthesis, and on CA biosynthetic enzyme activities and gene expression at baseline and during immobilization stress (IMO). Adrenalectomy (ADX) stimulated basal and stress-induced increments in norepinephrine release, reuptake, metabolism, turnover, and biosynthesis. Loss of adrenomedullary hormones after ADX did not appear to contribute to these increments. Cortisol treatment reversed the ADX effects on CA indices and suppressed catecholaminergic responses to IMO in intact rats. These results suggest that endogenous glucocorticoids restrain responses of catecholamine turnover, synthesis, release, reuptake, and metabolism during stress. In contrast, in intact rats, continuous administration of cortisol lasting for 7 days exaggerated the IMO-induced increases in plasma CA levels. Inhibition of DOPA conversion to dopamine elevated plasma DOPA levels in chronically cortisol-treated stressed rats compared to saline-treated ones, suggesting a cortisol-induced increase in tyrosine hydroxylation. Stress increases TH and PNMT activities and mRNA levels in the adrenal medulla. Hypophysectomy reduced adrenal PNMT but not TH mRNA levels in control and IMO rats. Pretreatment of hypophysectomized animals with ACTH fully restored the control and IMO-induced adrenal PNMT mRNA levels and augmented PNMT but not TH mRNA responses in intact rats. Long-term cortisol administration to intact rats also elevated adrenal PNMT but not TH mRNA levels. The results indicate a suppressive effect of endogenous glucocorticoids and a stimulatory effect of chronically elevated glucocorticoid levels on sympathoadrenal activity during stress. The results also suggest that a nonneuronal, nonpituitary factor contributes to TH gene expression during some forms of stress, whereas pituitary-adrenocortical factors play the essential role in the regulation of PNMT gene expression.

Sympathetic suppression attenuates anomalous responses to morphine in unexplained pain after cholecystectomy

Anomalous responses to morphine are common in patients with unexplained pain in the upper abdomen after cholecystectomy and may be linked to activation of the sympathetic nervous system. The hypothesis that sympathetic suppression would attenuate anomalous responses to morphine was tested by a randomized, cross-over trial using a standard challenge with morphine, with and without pretreatment with clonidine (300 micrograms orally, 1 h prior to the administration of morphine). In 13 of the 15 patients who completed the study, pre-treatment with clonidine decreased plasma concentrations of noradrenaline, dopamine and adrenaline by 56, 15 and 25% respectively. This was associated with a significant reduction in morphine-induced pain (p = 0.02) and nausea (p = 0.04) and attenuated increases in plasma aspartate aminotransferase (AST) activity (p = 0.03). Clonidine attenuates anomalous responses to morphine, perhaps through effects on sympathetic nervous activity or plasma concentrations of catecholamines.

Differential glucocorticoid effects on catecholamine responses to stress

There have been relatively few studies of the relationships between glucocorticoid and catecholamine responses to stress. We have therefore determined plasma levels of adrenocorticotropic hormone (ACTH), cortisol (F), norepinephrine (NE), and epinephrine (Epi) in four intact sheep treated with cortisol, dexamethasone (DM), or saline (S) and subjected to both audiovisual (barking dog) and insulin-induced hypoglycemic stress. In control sheep, exposure to both stressors resulted in acute rises in ACTH, F, Epi, and NE, with the rises after insulin being greater than those after dog stress. Pretreatment with DM blocked the ACTH and F responses to stress. Both DM and F markedly attenuated the Epi response to hypoglycemia, whereas the rises in NE after each stress and those of Epi after dog stress were unaffected by steroid treatment. In a second experiment with six sheep treated with S or DM only and subjected to the same stressors in reverse order, the same results were obtained, excluding a confounding effect of prior stress. We conclude that 1) the poststress release of NE, presumably primarily from extra-adrenal sources, is largely steroid independent; 2) the mechanism of release of Epi from the adrenal medulla in response to audiovisual stress is different from that after hypoglycemia; and 3) this may reflect different inputs from central glucocorticoid receptors to splanchnic outflow in the two situations.