Mechanisms of activation of the pituitary-adrenal axis by tissue injury in the rat

To characterize the mechanisms of the pituitary-adrenal (P-A) response to tissue injury, rats were injected intramuscularly (IM) with turpentine. This resulted in marked elevations in the plasma concentrations of ACTH and corticosterone within the first hour after injection, which were attenuated by either total deafferentation of the medial basal hypothalamus (MBH) or neonatal capsaicin pretreatment. The plasma concentrations of corticosterone remained elevated for 18 h in the turpentine-injected rats, despite a return of ACTH toward control values (by 2-4 h). Bioactive concentrations of interleukin-6 (IL-6) in plasma rose markedly after turpentine, and its concentrations were significantly correlated with plasma corticosterone concentrations 4-8 h after turpentine. Pretreatment with IL-1 receptor antagonist (IL-1ra) attenuated the release of IL-6 and had a marginal effect on the corticosterone response 6 h after turpentine. These results suggest that the early and late phase of the P-A response to tissue injury are mediated by different mechanisms.

ANP(5-28) is the major molecular species in hypophysial portal blood of the rat

We have previously demonstrated that the concentrations of immunoreactive atrial natriuretic peptide (IR-ANP) are significantly higher in hypophysial portal compared with peripheral blood of the rat, and that ANP suppresses the pituitary release of ACTH and beta-endorphin in vitro and in vivo. Using HPLC, we have now shown that the predominant species of IR-ANP in extracts of portal blood from adult male and female rats is ANP(5-28), whereas in peripheral blood, ANP(1-28) predominates. The ratio of ANP(5-28) in portal compared with peripheral blood was 4.2 in male and 4.8 in female animals.

The effects of the modified intermittent sequential pneumatic device (MISPD) on exercise performance following an exhaustive exercise bout

The Lymphapress, a pneumatic sequential intermittent device is recognized as one of the most effective conservative treatments for lymphoedema, due to its effective 'milking mechanism'. This led us to hypothesize that accelerated removal of fatigue-causing metabolites by mechanical massage could improve an athlete's performance capacity. We conducted trials with 11 men who exercised at a constant workload, on a cycle ergometer, until exhaustion. During a 20-min recovery period a new modified pneumatic sequential intermittent device (the MISPD) was applied to the subjects' legs. The men then performed a second constant load exercise bout. Cardiorespiratory parameters were measured during exercise and blood was withdrawn during recovery for the determination of lactate, pyruvate, ammonia, bicarbonate and pH. No difference was found in the blood levels of the 'fatigue causing metabolites' during passive recovery (PR) and recovery with the MISPD (MR). However, the MISPD effected a 45% improvement in the subjects' ability to perform the subsequent exercise bout. The accumulation of fluid in the interstitial space after exercise and its disappearance after the use of the MISPD offers one possible explanation for these results, although psychological effects cannot be discounted.

External high-frequency ventilation in severe chronic obstructive pulmonary disease

We studied the effect of external high-frequency oscillation using an oscillator (Hayek oscillator [HO]) on 20 patients with severe chronic obstructive pulmonary disease (COPD). Of the 20 patients, 10 were eucapnic and 10 were hypercapnic. The HO generated frequencies from 60 to 140 cycles/min at an amplitude of 36 cm H2O (-26 to +10) and at an inspiratory/expiratory (I/E) ratio of 1:1. The results show that the HO is a powerful ventilator, reducing end-tidal PCO2 (PETCO2) by 6.7 to 9.1 mm Hg in eucapnic patients and by 6.1 to 7.9 mm Hg in hypercapnic patients. The oxygen saturation increased by 2 to 2.87 percent in the eucapnic patients and by 2.6 to 3.7 percent in the hypercapnic group in the various frequencies. The rate of elimination of CO2 and the levels of PETCO2 achieved within a short time were superior to those reported with other external ventilators. We conclude that the HO can be effectively used in severe COPD and respiratory failure for (1) assisting ventilation, thus replacing intubation and conventional mechanical ventilation, and (2) relieving muscle fatigue in short sessions.

The VIP2 receptor: molecular characterisation of a cDNA encoding a novel receptor for vasoactive intestinal peptide

We have cloned and sequenced a cDNA (RPR4) encoding a new member of the secretin/calcitonin/parathyroid hormone (PTH) receptor family. RPR4 was identified by PCR of rat pituitary cDNA, and a full-length clone was isolated from a rat olfactory bulb cDNA library. When RPR4 was functionally expressed in COS 7 cells, cyclic adenosine monophosphate (cAMP) production was stimulated by vasoactive intestinal peptide (VIP), pituitary adenylate cyclase activating peptides (PACAP-38 and PACAP-27) and helodermin, with equal potency. Peptide histidine isoleucine (PHI) and rat growth hormone releasing hormone (rGHRH) also stimulated cAMP production at lower potency. This suggests that RPR4 encodes a novel VIP receptor which we have designated the VIP2 receptor. In situ hybridisation showed that mRNA for this receptor was present mainly in the thalamus, hippocampus and in the suprachiasmatic nucleus.

Molecular cloning and expression of a cDNA encoding a receptor for pituitary adenylate cyclase activating polypeptide (PACAP)

We have cloned and sequenced a novel cDNA (RPR7) encoding a receptor for pituitary adenylate cyclase activating polypeptide (PACAP). RPR7 was identified by PCR of rat pituitary cDNA, and full-length clones were isolated from a rat olfactory bulb cDNA library. When expressed in COS cells, RPR7 was functionally coupled to increases in intracellular cyclic adenosine monophosphate (cAMP) in response to stimulation by PACAP-38, PACAP-27, vasoactive intestinal peptide (VIP) and peptide histidine isoleucine (PHI). The order of potency of these ligands was PACAP-38-PACAP-27 > VIP > PHI, suggesting that the receptor corresponds to the pharmacologically characterised PACAP Type I receptor.

The effects of adrenalectomy and ovariectomy on the behavioral and hypothermic responses of rats to 8-hydroxy-2(di-n-propylamino)tetralin (8-OH-DPAT)

The aim of this study was to determine the effects of sex, corticosterone and oestradiol-17 beta on the hypothermia and motor behavioural syndrome induced by the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) in the rat. The hypothermia, but not the behavioural syndrome induced by 8-OH-DPAT was significantly greater in female compared with male rats. Adrenalectomy in male rats enhanced the hypothermic response, an effect prevented by corticosterone implants. Ovariectomy significantly attenuated the hypothermia induced by 8-OH-DPAT, an effect prevented by oestradiol-17 beta implants. Neither type of steroid manipulation affected the behavioural syndrome. These results show that sex, corticosterone and oestradiol-17 beta modulate the hypothermic response to 8-OH-DPAT in the rat, with corticosterone and oestradiol-17 beta having opposing effects.

Positron emission tomography in myotonic dystrophy

Regional cerebral glucose metabolism (rCMRG1) was studied in three patients with myotonic dystrophy by positron emission tomography with 18F-2-fluoro-2-deoxy-D-glucose as the radiotracer. Clinically, all patients presented an organic personality syndrome. Impairment of rCMRG1 was found in all cortical and subcortical regions, particularly in the frontal cortex and the lentiform nucleus. The results suggest that the organic personality changes that occur in myotonic dystrophy reflect widespread cerebral pathology. The metabolic pattern was similar to that seen in normal aging but was qualitatively more severe and is therefore consistent with the classification of myotonic dystrophy as a progeric disease.

Glucocorticoid receptor gene expression is unaltered in hippocampal neurons in Alzheimer's disease

Excessive glucocorticoid levels increase the metabolic vulnerability of hippocampal neurons to a wide variety of insults. Since glucocorticoid hypersecretion occurs in Alzheimer's-type dementia it has been proposed that a primary reduction in hippocampal glucocorticoid receptor expression leads to failure of feedback, hypercortisolemia and hence further neuronal loss. However, we have recently found that lesions of the cholinergic innervation of the hippocampus--known to be severely affected in Alzheimer's disease--increase corticosteroid receptor gene expression in the rat hippocampus. We have now examined both glucocorticoid (GR) and mineralocorticoid (MR) receptor gene expression in individual neurons in human postmortem hippocampus, using in situ hybridization histochemistry in 5 patients with Alzheimer's disease (81 +/- 3 years) and 7 controls (81 +/- 7 years) without neurological disease. The distribution and intensity of MR and GR mRNA expression in the hippocampus of Alzheimer's disease were similar to that in control tissue, with high expression in dentate gyrus and CA2-4, but significantly lower expression in CA1. In a separate group of patients with Alzheimer's disease we found significantly increased 24 h integrated plasma cortisol levels (59% greater than age-matched controls) and reduced cortisol-binding globulin (21% lower). These data do not suggest a primary deficiency of biosynthesis of hippocampal corticosteroid receptors in Alzheimer's disease. The maintenance of hippocampal GR and MR gene expression, in the face of an increased glucocorticoid feedback signal, may reflect loss of the cholinergic innervation.

Suture granuloma simulating lung neoplasm occurring after segmentectomy

A suture granuloma was resected which developed after segmentectomy of a squamous cell carcinoma of the lung and radiologically mimicked a neoplasm. This report emphasises that although the appearance of the lesion may be typical for malignancy, the possibility of a benign suture granuloma should be considered, especially if the lesion appears shortly after surgery.

The 11 beta-hydroxysteroid dehydrogenase inhibitor glycyrrhetinic acid affects corticosteroid feedback regulation of hypothalamic corticotrophin-releasing peptides in rats

Steroid-metabolizing enzymes modulate the effects of androgens on brain differentiation and function, but no similar enzymatic system has been demonstrated for adrenocorticosteroids which exert feedback control on the hypothalamus. 11 beta-Hydroxysteroid dehydrogenase (11 beta-OHSD) rapidly metabolizes physiological glucocorticoids (corticosterone, cortisol) to inactive products, thereby regulating glucocorticoid access to peripheral mineralocorticoid and glucocorticoid receptors in a site-specific manner. Using in-situ hybridization, we found expression of 11 beta-OHSD mRNA in neurones of the hypothalamic paraventricular nucleus (PVN) where corticotrophin-releasing factor-41 (CRF-41) is synthesized and from where it is released into hypophysial portal blood. Administration of glycyrrhetinic acid (GE), a potent 11 beta-OHSD inhibitor, decreased CRF-41 release into hypophysial portal blood in the presence of unchanged circulating glucocorticoid levels, suggesting that 11 beta-OHSD regulates the effective corticosterone feedback signal to CRF-41 neurones. These effects of GE were not observed in adrenalectomized animals, demonstrating dependence on adrenal products. In contrast, GE led to two- to threefold increases in arginine vasopressin and oxytocin release into portal blood, effects also dependent upon intact adrenal glands. These results suggest that 11 beta-OHSD in the PVN, and possibly other sites, may represent a novel and important control point of corticosteroid feedback on CRF-41 release in vivo.

Assessment of exercise capacity in asthmatic children with various degrees of activity

Physical fitness in a group of 49 stable asthmatic children was determined by an incremental exercise test. Thirty-one normal children served as a control group. The asthmatic children were divided into three groups. Group 1 was comprised of 16 children who actively participated in organized sports, Group 2 of 16 children who did not participate in organized sports but who engaged in free-play, and Group 3 of 17 children with a sedentary life-style who avoided even free-play. The results of cardiopulmonary evaluation before and after maximal incremental exercise testing have shown that Groups 1 and 2 behaved like the control group and their physical fitness was similar. Group 3 whose life-style was sedentary had poor physical fitness as compared to the other asthmatics and to the control group. This was the result of poor cardiovascular conditioning and was unrelated to the respiratory limitation. We conclude that poor physical fitness in asthmatic children is the result of a sedentary life-style and can be potentially normalized.

The effects of cortisol infusion upon hormone secretion from the anterior pituitary and subjective mood in depressive illness and in controls

The aims of this study were to determine whether the administration of cortisol has a significant effect on mood in patients with depression and whether the effects of cortisol on changes in plasma hormone concentrations are like those of synthetic corticosteroids. Twelve patients had major depression and one each had dysthymic disorder and a depressive adjustment disorder. Five were male and nine were female. All were in-patients. Eight normal subjects, two females and six males, were used as controls. Basal beta-endorphin concentrations were 2- to 3-fold higher in depressed patients than in control subjects, but there were no significant differences between the patient and control groups in the basal (pre-infusion) plasma concentrations of ACTH, cortisol, growth hormone or prolactin. Cortisol, but not saline infusion resulted in a significant improvement in self rated mood. Surprisingly, cortisol infusion at first increased plasma beta-endorphin concentrations. At later times after cortisol infusion, plasma beta-endorphin concentrations decreased as did the plasma concentrations of ACTH and growth hormone; prolactin levels were increased. These results show (i) that cortisol infusion raises mood significantly in major depression, (ii) that plasma beta-endorphin concentration is a potential marker of major depression (iii) that rather than blunting of corticosteroid effects, responses to cortisol may even be enhanced in depressive illness. The unexpected, initial increase in beta-endorphin stimulated by cortisol, suggests that the action of cortisol is not simply one of negative feedback inhibition, but may involve mineralocorticoid, as well as glucocorticoid receptors.

Oestrogen positive feedback reduces arcuate proopiomelanocortin messenger ribonucleic Acid

Oestradiol-17ß, in its positive feedback mode, as well as stimulating the release of luteinizing hormone-releasing hormone. (LHRH), also stimulates LHRH mRNA synthesis in medial preoptic neurons. Our aim was to determine whether the action of oestradiol might be mediated in part by inhibiting arcuate proopiomelanocortin (POMC) neurons which terminate on LHRH neurons. Female rats were ovariectomized at about 1000 h of dioestrus, given a subcutaneous injection of oil or oestradiol benzoate and killed at 1600 h the same day (presumptive dioestrus), presumptive pro-oestrus and oestrus and at 1000 h of presumptive pro-oestrus. In situ hybridization of brain sections was carried out with a [(35) S]UTP-labelled riboprobe containing 538 bases of a cDNA identical to exon 3 of the POMC gene, which includes the ß-endorphin coding domain. The amount of POMC mRNA in cells of the anterior arcuate nucleus, as assessed by grain counts, was significantly decreased in oestradiol benzoate- compared with oil-treated animals at 1600 h of pro-oestrus, but at none of the other times studied. This finding, together with other data, suggests that the positive feedback stimulation of LHRH mRNA synthesis by oestradiol-17ß may be due, in part, to the disinhibition of LHRH neurons consequent on inhibition of POMC mRNA biosynthesis in arcuate neurons.

Atrial natriuretic peptide is involved in the ACTH response to stress and glucocorticoid negative feedback in the rat

The role of atrial natriuretic peptide (ANP) in the ACTH response to stress and the glucocorticoid negative feedback control of ACTH release was investigated in adult male homozygous Brattleboro and adrenalectomized Wistar rats respectively, using the technique of immunoneutralization. The relatively low ACTH response to stress and the lack of arginine vasopressin make the homozygous Brattleboro rat a more rigorous and simpler preparation in which to test the hypothesis that ANP is involved in the ACTH response to stress. In both sets of experiments, blood sampling and injection of sheep anti-ANP or control serum were carried out in conscious animals through intra-atrial cannulae implanted 2 days previously under halothane anaesthesia. A 30-s exposure to ether resulted in a brisk twofold increase in the plasma ACTH concentrations in homozygous Brattleboro rats infused with anti-ANP, but not control serum. The injection of either dexamethasone, a potent glucocorticoid receptor agonist, or corticosterone resulted in a rapid and marked reduction in the plasma concentrations of ACTH in Wistar rats which had been adrenalectomized, under halothane anaesthesia, at least 21 days before experimentation. The inhibitory action of dexamethasone, but not corticosterone, was significantly reduced in animals infused with anti-ANP serum. These results show that the inhibition of ANP release into hypophysial portal blood is probably important for triggering the ACTH response to stress and that ANP may play a role in corticosteroid negative feedback control of ACTH release mediated by type II (glucocorticoid) receptors.

Antidepressants increase glucocorticoid and mineralocorticoid receptor mRNA expression in rat hippocampus in vivo

Adrenal corticosteroids bind to hippocampal glucocorticoid (GR) and mineralocorticoid receptors (MR), thereby affecting neurochemical transmission leading to altered mood, behaviour and neuroendocrine control. Serotoninergic (5-HT) and noradrenergic projections innervate the hippocampus, interacting with corticosteroid-sensitive cells. We have previously demonstrated that lesions of 5-HT neurons reduce hippocampal GR and MR mRNA levels and now examine whether acute or chronic treatment with antidepressant drugs, which potentiate endogenous monoamines by inhibiting their reuptake, affect hippocampal GR and MR mRNA expression in vivo. Rats were treated with amitriptyline (20 mg/kg.day-1), desipramine (10 mg/kg.day-1) or citalopram (20 mg/kg.day-1). After 2 or 14 days animals were killed, RNA extracted and GR and MR mRNA expression quantified by slot blot hybridization. Amitriptyline for 2 days led to a significant increase in MR (by 23 +/- 6%, compared with saline-treated controls), but not GR, mRNA expression. After 14 days amitriptyline, expression of both MR (87 +/- 27% rise) and GR mRNA (56 +/- 18% rise) had increased significantly in hippocampus, but not in parietal cortex. Desipramine for 14 days also increased MR (60 +/- 9%) and GR (42 +/- 9%) mRNA expression, though 14 days of citalopram altered only MR mRNA expression (17 +/- 5%). Thus, antidepressant drug administration elevates MR and GR mRNA expression in hippocampus, but not parietal cortex, in a time-dependent manner.

Medial septal cholinergic lesions increase hippocampal mineralocorticoid and glucocorticoid receptor messenger RNA expression

Loss of the cholinergic innervation of the hippocampus and failure of central (presumably hippocampal) suppressive control of hypothalamic-pituitary-adrenal axis activity are important features of Alzheimer's dementia. We have examined the effects of electrolytic lesions of the medial septal cholinergic innervation on mineralocorticoid (MR) and glucocorticoid (GR) receptor mRNA expression in rat hippocampus using in situ hybridization histochemistry. Expression of both MR and GR mRNA was significantly increased in a subregions of the hippocampus, but not neocortex, with the greatest increase in the CA1 area for MR mRNA and dentate gyrus for GR mRNA. Since glucocorticoids potentiate the effects of neurotoxins in the hippocampus, the increased expression of receptors following loss of cholinergic inputs in Alzheimer's disease may increase hippocampal neuronal vulnerability.