Evaluation of deep gray matter volume, cortical thickness and white matter integrity in patients with typical absence epilepsy: a study using voxelwise-based techniques.

INTRODUCTION: The objective of this study was to evaluate the cortical thickness and the volume of deep gray matter structures, measured from 3D T1-weighted gradient echo imaging, and white matter integrity, by diffusion tensor imaging (DTI) in patients with typical absence epilepsy (AE). METHODS: Patients (n = 19) with typical childhood AE and juvenile AE, currently taking antiepileptic medication, were compared with control subjects (n = 19), matched for gender and age. 3D T1 magnetization-prepared rapid gradient echo-weighted imaging and DTI along 30 noncolinear directions were performed using a 1.5-T MR scanner. FreeSurfer was used to perform cortical volumetric reconstruction and segmentation of deep gray matter structures. For tract-based spatial statistics analysis of DTI, a white matter skeleton was created, along with a permutation-based inference with 5000 permutations. A threshold of p < 0.05 was used to identify abnormalities in fractional anisotropy (FA). The mean, radial, and axial diffusivities were also projected onto the mean FA skeleton. RESULTS: Patients with AE presented decreased FA and increased mean diffusivity and radial diffusivity values in the genu and the body of the corpus callosum and right anterior corona radiata, as well as decreased axial diffusivity in the left posterior thalamic radiation, inferior cerebellar peduncle, right cerebral peduncle, and right corticospinal tract. However, there were no significant differences in cortical thickness or deep gray matter structure volumes between patients with AE and controls. CONCLUSION: Abnormalities found in white matter integrity may help to better understand the pathophysiology of AE and optimize diagnosis and treatment strategies.

Inhibition of leukocyte chemotaxis by factor in alloxan-induced diabetic rat plasma.

The early local exudative cellular reaction in an inflammatory lesion was impaired in alloxan-induced diabetic rats due to reduced migration of neutrophils to the inflamed area. Neutrophils, however, were capable of moving from reserve compartments into blood in these animals. Furthermore, the functional integrity of their surface membranes, assessed by the capacity of the cells to adhere to nylon fiber, was not altered by alloxan diabetes. An intrinsic cellular defect also did not occur, because the cells were capable of responding to chemotactic stimuli in the Boyden chamber system, provided they were suspended in Eagle's medium or normal serum. Suspended in the corresponding diabetic serum, a blockade of the chemotactic response was observed. Increasing concentrations of diabetic serum, added to a suspension containing neutrophils collected from normal donors, progressively inhibited the response of the cells to a chemotactic stimulus. Hyperglycemia alone or hyperosmolality secondary to hyperglycemia, the presence of ketone bodies, or a direct effect of alloxan did not explain the results. In addition, the capacity to generate chemotactic factors remained intact in diabetic serum. Pretreatment of the diabetic animals with insulin resulted in a gradual recovery of the chemotactic response in vivo and in vitro. We conclude that alloxan-induced diabetic rat serum contains a substance that inhibits neutrophil chemotaxis and that insulin administration is essential for the clearance of this substance from plasma.

Direct vital microscopic study of defective leukocyte-endothelial interaction in diabetes mellitus.

The number of leukocytes rolling along the venular endothelium of the vascular network of the internal spermatic fascia was determined in nondiabetic control rats and diabetic rats with television microscopy. A marked decrease in the number of rolling cells was observed in animals rendered diabetic by the injection of alloxan 10, 30, or 180 days before relative to matching controls. Blood leukocyte counts, however, were equivalent in both control and diabetic rats. Under the influence of a local inflammatory stimulus, cells emerged into the perivascular tissue in control animals, and this was accompanied by a reduction in the number of rolling leukocytes. In diabetic rats, the number of rolling leukocytes remained unaltered, and only a few cells accumulated in the connective tissue adjacent to the vessel. Reversal of the defective leukocyte-endothelial interaction was attained by treatment of diabetic animals with insulin. Inhibitors of arachidonic acid metabolism were ineffective to improve leukocyte-endothelial interactions in diabetic animals. Control rats injected intravenously with lyophilized plasma constituents, obtained after dialysis of diabetic rat plasma with 12,000-Mr retention dialysis tubing, behaved as diabetic animals in that they exhibited a reduced number of leukocytes rolling along the venular endothelium. In contrast, material obtained from control rat plasma produced no effect. Heating of active samples for 1 h at 56 degrees C resulted in the complete loss of the inhibitory effect. We conclude that a substance or substances present in diabetic plasma induce a defective leukocyte-endothelial interaction that further impairs resistance to infection.

Secreted glucocorticoids regulate leukocyte-endothelial interactions in inflammation. A direct vital microscopic study.

Leukocytes come into intimate contact with the venular endothelium as they extravasate from blood to the interstitium during inflammation. In exteriorized tissues, the number of leukocytes rolling along the vessel wall was markedly increased in adrenalectomized and metyrapone-treated animals, relative to sham-operated and normal animals. During the development of an acute, local inflammatory response, rollers were numerically decreased and a stronger adhesion of the cells to the endothelium, with a concomitant migration into tissues, was observed. Adhesion and migration were much more marked in adrenalectomized and metyrapone-treated animals than in controls, suggesting that secreted glucocorticoids exert a suppressive effect on leukocyte-endothelial interactions. The increased number of rolling leukocytes in adrenalectomized and metyrapone-treated animals apparently resulted in more cells available to migrate into inflamed tissues. The effect appears to involve receptor occupancy and induction of gene expression because normal animals receiving the steroid antagonist RU 38 486, actinomycin D, or cycloheximide behaved as adrenalectomized or metyrapone-treated animals. Administration to adrenalectomized animals of a monoclonal antibody to the membrane glycoprotein complex CD18 did not affect the number of rolling cells, but dramatically reduced the number of adherent or migrated leukocytes. It is suggested that secreted glucocorticoids, in addition to an effect on rolling behavior of circulating leukocytes, might also modulate the activity of the glycoprotein complex CD18 on white blood cells. The ultimate consequence is a restrictive effect on cell emigration in inflammation.

Inhibition of neutrophil chemotaxis and chemokinesis associated with a plasma protein in aging rats: selective depression of cell responses mediated by complement-derived chemoattractants.

The influence of aging on neutrophil chemotaxis, chemokinesis, and superoxide production was investigated in rats. Animals of two age groups, 3 to 4 months and 20 to 21 months, were used. Equivalent neutrophil chemotactic responses to N-formyl-methionyl-leucyl-phenylalanine (fMLP), leukotriene B4 (LTB4), and bacterial lipopolysaccharide (LPS)-activated plasma were observed in both groups of animals, with cells suspended in Hanks' balanced salt solution (HBSS). However, cross-incubation studies in which cells from young adult rats were exposed to plasma from aged donors, then resuspended in HBSS for testing, showed marked changes in the ability of the cells to respond to the chemoattractants. The response to LPS-activated plasma was reduced, whereas responses to fMLP and LTB4 remained unaltered. Previous incubation of the cells with homologous plasma from young donors produced no effect. The inhibitory activity developing with advancing age affected not only chemotaxis but also random movement stimulated by LPS-activated plasma. The inhibitory activity of chemotaxis and chemokinesis in plasma of aged animals was heat labile (56 degrees C), vanished in the presence of a proteolytic enzyme like trypsin, and was maintained after dialysis with 12,000-Mr retention dialysis tubing. The material did not influence superoxide production by stimulated neutrophils. It is suggested that inhibition of neutrophil locomotion with advancing age is associated with a plasma protein capable of interacting with neutrophil receptors for complement-derived chemoattractants. The inhibitory substance might influence neutrophil responses to infection and inflammation in the elderly.

Cortical potentials evoked by nociceptive stimuli: their depression by a factor released during saphenous nerve stimulation in the rat.

1 The amplitudes of the first positive and the first negative waves of cortical potentials evoked by electrical stimulation of the dental pulp in the rat were decreased following electrical stimulation of the peripheral cut end of the saphenous nerve.2 This effect was greatly diminished when the stimulation of the saphenous nerve was performed with the saphenous or femoral veins ligated.3 During stimulation of the saphenous nerve of a donor rat, the subcutaneous tissue in the area supplied by the nerve was perfused; when the perfusate (in which a permeability-increasing factor was detected) was injected intravenously into a recipient animal, a decrease in the amplitude of the evoked cortical potential of the recipient rat was also observed.4 Intravenous injections of 5-hydroxytryptamine, histamine, bradykinin, prostaglandins or adenosine-triphosphate produced no effect on the evoked cortical potential, whereas large doses of acetylsalicylic acid caused a decrease.5 It is suggested that a humoral factor, released during sensory nerve stimulation, may help to modulate the processing of afferent inputs from pain receptors.

Formation of a factor increasing vascular permeability during electrical stimulation of the saphenous nerve in rats.

1 Increased vascular permeability following electric antidromic stimulation of the rat saphenous nerve was observed in the skin area supplied by the nerve, confirming previous results by other authors.2 The phenomenon was not affected by pretreatment of the rats with diphenhydramine, burimamide or their combination; atropine, methysergide, methysergide plus diphenhydramine, carboxypeptidase B, acetylsalicylic acid, indomethacin or methiazinic acid. It was partially reduced by previous injection of cellulose-sulphate, a kininogen-depleting agent.3 Perfusates from the subcutaneous tissue of the paw area supplied by the saphenous nerve contained permeability increasing activity as shown by intradermal tests in other rats. This activity was present in perfusates collected during nerve stimulation but not in those collected before stimulation. It was not destroyed by heating to 100 degrees C, or by alpha-chymotrypsin or trypsin.4 Bradykinin-like activity may appear later in the perfusates, depending on the intensity of the stimuli.5 It is concluded that following electrical antidromic stimulation of the saphenous nerve a permeability increasing factor is released, possibly from nerves. It is dialysable and can be distinguished from acetylcholine, histamine, 5-hydroxytryptamine, plasma kinins, substance P, prostaglandins and high molecular weight proteins. The increased vascular permeability induced by this factor leads to plasma exudation and activation of the kinin system.

Stimulation of the hypothalamo-pituitary-adrenal axis by compounds formed in inflamed tissue.

1 Rat paws were injected with carrageenin, and their subcutaneous tissue perfused 135 min later. These perfusates were injected intravenously into receptor rats in which they caused an attenuation of inflammatory responses. 2 The effect was not observed in adrenalectomized receptor rats nor in receptors with electrolytic lesions in the median eminence of the hypothalamus but persisted in adrenal-demedullated animals. 3 The active perfusates also induced eosinopenia in normal or adrenal-demedullated animals, but not in adrenalectomized rats, and produced an increase in blood corticosterone with a concomitant decrease in the amounts of adrenal ascorbic acid. 4 The active perfusates did not affect the responses of isolated preparations to histamine, bradykinin, prostaglandins and 5-hydroxytryptamine neither did they elicit changes of the arterial blood pressure in receptor animals. 5 The anti-inflammatory activity present in perfusates from inflamed paws seems to be formed slowly at the site of the developing inflammatory reaction, since perfusates collected 30-65 min after the injection of carrageenin were ineffective, as was plasma taken from donor rats at various time intervals after carrageenin injections. 6 It is suggested that the anti-inflammatory factor present in the active perfusates exerts its action by stimulation of the hypothalamo-pituitary-adrenal axis.

Vascular reactivity in diabetes mellitus: possible role of insulin on the endothelial cell.

The response to vasoactive agents of microvessels of the rat was tested in vivo by direct microscopic observation of the exteriorized mesentery and assessment of cutaneous vascular permeability changes with Evans blue. The constrictor response to a standard amount of noradrenaline in mesenteric microvessels was fully antagonized by acetylcholine in normal, diabetic, adrenalectomized and diabetic-adrenalectomized rats. In contrast, the minimum doses of histamine or bradykinin, effective in normal or adrenalectomized animals, had to be increased about 20 fold to be active in diabetic or diabetic-adrenalectomized animals. Topical application of insulin to mesenteric microvessels of diabetic animals, in amounts not causing any increase in serum insulin levels, improved or restored the capacity of the animals to respond to histamine or bradykinin, acting as antagonists of the vasoconstrictor response to noradrenaline. Topical insulin, however, was ineffective in normal animals given 2-deoxyglucose, the acute effects of which result from cellular glucopaenia unrelated to insulin deficiency. Vascular permeability responses to intracutaneous histamine or bradykinin were decreased in animals pretreated with 2-deoxyglucose as much as in diabetic animals. Pretreatment of normal animals with indomethacin produced no effect on the responses of these animals to histamine or bradykinin, tested as antagonists of noradrenaline on mesenteric microvessels, or as vascular permeability-increasing factors in the skin. Pretreatment of normal animals with chloroquine, mepacrine or dexamethasone had no effect on the reactivity of mesenteric microvessels to histamine and bradykinin, acting as antagonists to noradrenaline. 7 It is suggested that vasoactive substances, endowed with permeability-increasing properties, evoke relaxation of microvessels through an insulin-dependent action on endothelial cells, unrelated to the release of arachidonic acid metabolites. This action would lead to increased vascular permeability, with opening of interendothelial junctions, and temporary changes in composition of extravascular fluid, which in turn, would provide the basis for vasodilatation. Diabetes mellitus apparently impairs such responses as a result of the accompanying cellular glucopaenia. Adrenal corticosteroids are not involved in the impaired responses.

Influence of diabetes on the reactivity of mesenteric microvessels to histamine, bradykinin and acetylcholine.

1 Noradrenaline (NA) evoked a vasoconstrictor response in rat mesenteric microvessels in situ, the latency and nature of which was analogous in normal and alloxan-diabetic animals.2 Histamine and bradykinin (Bk) were capable of antagonizing the response to NA in normal but not in diabetic animals. In contrast, acetylcholine (ACh) was equally effective as an antagonist to NA in both groups of animals.3 The altered responses to histamine and Bk were not associated with hyperglycaemia since fasting rendered the diabetic animals normoglycaemic and yet did not restore the reactivity of microvessels. Previous administration of insulin to diabetic animals corrected the impaired responses to histamine and Bk.4 A similar condition of impaired responses to histamine and Bk was produced in normal animals by the intravenous injection of 2-deoxyglucose although ACh remained fully active.5 Apparently, the functional changes observed in the response to histamine or Bk, as antagonists of the vasoconstrictor reaction to NA, were not associated with a defective response of all smooth muscle. First, because ACh remained active in diabetic animals, and, second, because extravascular smooth muscles obtained from either normal or diabetic rats were equally relaxed by histamine or Bk in vitro.6 It is suggested that histamine and Bk antagonized the vasoconstrictor response of microvessels to NA through an action on lining endothelial cells resulting in increased vascular permeability and hyperosmolarity of extracellular fluids.7 The process depended on the availability of insulin, and, therefore, might be affected by intracellular glucopaenia as occurring in diabetes.8 Intracellular glucopaenia markedly affected other structures. Reduced atria rates were observed in diabetes, despite the fact that the isolated preparation responded normally to NA, ACh or tyramine. Partial substitution of glucose in the bathing fluid by 2-deoxyglucose or addition of NaF to the organ bath evoked similar changes in atria from normal animals.9 ACh which has little effect on vascular permeability must exert its vasodilator effects through mechanisms which are different from those influenced by the biochemical changes occurring in diabetes.

Vascular reactivity in diabetes mellitus: role of the endothelial cell.

The response to vasoactive agents of microvessels in situ and large arteries in vitro was compared in normal and alloxan-diabetic rats. Noradrenaline was equally effective in evoking a constrictor response of mesenteric microvessels in normal and diabetic animals. The constrictor response to a standard amount of noradrenaline in such vessels was fully antagonized by acetylcholine or papaverine, the minimum effective doses being equivalent in normal and diabetic animals. In contrast, the minimum doses of histamine or bradykinin, effective in normal animals, had to be increased about 20 fold to be active in diabetic animals. Increased osmolarity of extracellular fluid caused a significant and equivalent increase in latency of the vasoconstrictor response of microvessels to noradrenaline in normal and diabetic animals. Concentration-effect curves, constructed from the response of isolated aortae to noradrenaline, were similar in normal and diabetic animals, provided the endothelium was removed. Diabetes only affected preparations in which the endothelium was left intact. In these, the median effective concentrations of noradrenaline were greatly increased in comparison with normal values. Precontracted aortae from normal and diabetic animals were equally relaxed by acetylcholine and histamine, provided the endothelium was left intact. Loss of the relaxant response of the preparations in all groups of animals was observed following removal of endothelial cells. It is suggested that different mechanisms may be involved in the effects of vasodilator agents on large arteries in vitro or small vessels in situ. Histamine and bradykinin which are potent permeability-increasing factors, may antagonize the vasoconstrictor response of microvessels to noradrenaline through an action on endothelial cells with increased vascular permeability and temporary changes in composition of extracellular fluid. The reactive process of endothelial cells to permeability factors was affected by diabetes mellitus. However, the response of microvessels to acetylcholine and papaverine which are devoid of permeability-increasing properties, was not influenced by diabetes.

Anti-inflammatory action of glucagon in rats.

1 Subcutaneous administration of glucagon (1 and 0.5 mg/kg) 30 min before the injection of carrageenin or dextran into the rat's paw reduced oedema and the local exudation of Evans blue previously given intravenously. 2 The effect persisted after removal of the adrenal medulla but not after adrenalectomy. 3 When glucagon (1 mg/kg, s.c.) was given daily after a local reaction to Freund's adjuvant injected into the paw had developed, a decrease in the reaction was observed up to 12 days. Blood sugar levels remained within the normal range. 4 Glucagon may exert an anti-inflammatory effect through the release of adrenal corticosteroids and thus help modulate inflammatory reactions.

Effect of anti-proteases and hexadimethrine bromide on the release of a bradykinin-like substance during heating (46 degrees C) of rat paws.

1. The conditions in which the release of an active, bradykinin-like agent occurred when rat paws were heated to 46 degrees C were studied by means of the double coaxial perfusion of the subcutaneous spaces.2. The active material thus released stimulated the isolated rat uterus, produced a relaxing effect on the isolated rat duodenum, was destroyed by incubation with chymotrypsin and was potentiated by bradykinin-potentiating factor. LSD-25, in doses sufficient completely to block 5-hydroxytryptamine, did not affect the responses of the isolated uterus to the active material.3. The effects on this release of anti-proteases and hexadimethrine bromide, atropine and diphenhydramine were studied.4. Soy-bean trypsin inhibitor and hexadimethrine bromide added to the perfusion fluid produced a potent and reversible inhibition of the release of the active material; aprotinin and Kunitz inhibitor caused a temporary block.5. When administered intravenously, much larger doses of the substances were necessary to produce a similar block.6. Pretreatment of the animals with atropine plus diphenhydramine did not affect the release of the active kinin(s).7. Ligature of one iliac artery was followed by disappearance of the active material in the perfusate from the corresponding paw.8. These facts suggest that heating elicits a process leading to plasma extravasation and that the subcutaneous tissue is the chief site of release of the active material.

Pharmacological analysis of the acute inflammatory process induced in the rat's paw by local injection of carrageenin and by heating.

1. Local injection of carrageenin in the rat's paw produced oedema and leakage of dye which had been administered previously by the intravenous route. A net dissociation between both parameters was observed: while oedema developed slowly, maximal intensity being attained after 4-5 h, dye-leakage was maximum after 1 hour.2. Anti-inflammatory drugs such as acetylsalicylic acid and indomethacin were effective in reducing oedema and dye-leakage when given before the injection of carrageenin, but much less effective when given 30 or 60 min after carrageenin. Hexadimethrine bromide was effective in reducing dye-leakage also when given 1 h after the injection of carrageenin.3. Combined administration of benadryl and methysergide, before the injection of carrageenin caused only a slight reduction in oedema and dye-leakage.4. When the paws were heated (55 degrees C for 30 s) as a noxious stimulus the dissociation between maximal oedema and maximal dye-leakage was not observed, both phenomena running parallel. Pre-treatment of the animals with indomethacin did not afford any protection.5. These results suggest that the inflammatory reaction to mild stimuli (carrageenin in our experiments) develops through different phases: initially the increased vascular permeability involves extravasation of plasma proteins and that phase is followed by an increased permeability mainly to water. Stronger stimuli (heating in our experiments) produce an overlapping of both phases, probably by inflicting severe damage to the vascular bed of the affected area.6. The anti-inflammatory drugs employed affected chiefly the initial phase of the response.

Thyroid hormones and vascular reactivity: role of the endothelial cell.

Decreased maximal responses to noradrenaline, adrenaline and phenylephrine were observed in aortas isolated from rats pretreated with triiodothyronine and thyroxine for 8 days. In addition, a potent relaxant effect occurred when supramaximal concentrations of noradrenaline and adrenaline, but not of phenylephrine, were used. The relaxant effect was not observed in preparations in which the endothelium had been removed, and it was antagonized by propranolol added to the bathing fluid. Practolol was ineffective. In vivo, adrenaline and noradrenaline evoked pressor effects which were of shorter duration and smaller magnitude in hormone-treated animals than in the controls. Furthermore, a subsequent fall in blood pressure to below normal was observed, not only with adrenaline but also with noradrenaline, in animals receiving thyroid hormones. We conclude that when large amounts of thyroid hormones circulate in the body, large arteries are more prone to distention in the presence of increased quantities of released catecholamines, and resistance vessels are less responsive to their pressor effects due to a superimposing dilator effect. These changes might represent adaptative mechanisms in hyperthyroid states, and might depend on a greater sensitivity of endothelial beta 2-receptors to noradrenaline and adrenaline.

Endothelin-1 induces potent constriction of lymphatic vessels in situ.

The response of lymph vessels, arterioles and venules in the exteriorized rat mesentery to endothelin-1, vasopressin and norepinephrine was examined with the aid of high-resolution television microscopy. On a molar basis, endothelin-1 was more potent than vasopressin to contract the three types of vessels. Norepinephrine, which could constrict blood microvessels, did not act on lymph vessels. Acetylcholine, sodium-nitroprusside and isoproterenol were ineffective to block the constrictive responses of lymph vessels to endothelin-1 and vasopressin. At the same concentrations, however, acetylcholine and sodium-nitroprusside antagonized the responses of arterioles and venules to endothelin-1 and norepinephrine, whereas the responses of blood microvessels to vasopressin remained unaffected. Isoproterenol, at doses capable of blocking the response of the arterioles and venules to norepinephrine, did not interfere with the constriction induced by endothelin-1 and vasopressin on these vessels. It is suggested that endothelin-1 might play a role in the regulation of lymphatic contractility apart from its vasoconstrictor activity on blood vessels.

Platelet-activating factor (PAF-acether) and microcirculation: effect of Lyso-PAF and PAF-antagonists.

Topical application of a standard dose of noradrenaline (NA) to the anesthetized rat mesentery evoked a vasoconstrictor response the latency of which was increased in a dose-dependent way by previous addition of PAF-acether or histamine but not by Lyso-PAF. Lyso-PAF, however, blocked the antagonistic effect of PAF-acether to NA, the blockade being equivalent to that observed with PAF-antagonists (BN 52021 or WEB 2086) either injected iv, or applied topically. In contrast, the antagonistic action of histamine towards NA was not affected by Lyso-PAF or PAF-antagonists. Since platelet aggregation and leukocyte accumulation did not occur, PAF-acether appears to interact directly with microvessels to block vasoconstrictor stimuli, an effect antagonized by PAF-antagonists and the metabolite/precursor, Lyso-PAF.

Permeability factors in lymph draining inflamed tissues: effect of anti-inflammatory drugs.

1. Inflammatory responses were induced by the injection of carrageenin into the rat paw and lymph was collected by cannulation of the thoracic duct. Cell-free lymph samples were intracutaneously injected into a second group of rats to measure vascular permeability activity by local exudation of Evans blue. 2. The vascular permeability activity in lymph samples draining inflamed tissue was consistently higher than in lymph from normal controls. Activity increased with the development of inflammation, attaining maximum values 2 to 2.5 h after the injection of carrageenin. 3. The activity was reduced by pretreatment of lymph donors with indomethacin or soybean trypsin inhibitor. Pretreatment of the animals used to measure vascular permeability activity with diphenhydramine or methysergide attenuated their responses to the permeability factors present in lymph. Thus prostaglandins, kinins, vasoactive amines or their generating systems may have contributed to the total activity detected. 4. Pretreatment of lymph donors with corticosterone or glucagon, whose anti-inflammatory action is mediated by the release of endogenous corticosteroids, did not alter the amount of activity in lymph. 5. These data suggest that the formation of the permeability factors present in lymph draining inflamed tissue was not affected by corticosteroids. We conclude that corticosteroids do not exert their anti-inflammatory activity at this level.

Endocrine disorders render rats hyporeactive to non-steroidal but not to steroidal anti-inflammatory drugs.

The effect of cortisol (10 and 20 mg kg-1 day-1, sc), indomethacin (2 and 4 mg kg-1 day-1, po) and piroxicam (10 and 20 mg kg-1 day-1, po) on the proliferative component of inflammation was investigated in normal, diabetic, adrenalectomized and diabetic-adrenalectomized rats using the cotton pellet test. Whereas cortisol was equally effective in preventing granulation tissue formation in all groups of animals, indomethacin and piroxicam were much less active in animals with hormonal dysfunctions. Indomethacin and piroxicam reduced thymus weight of normal and diabetic animals as much as cortisol. This was taken to be a strong indication of the effect of these non-steroidal drugs on the adrenal cortex leading to increased secretion of adrenal corticosteroids. We conclude that at least part of the anti-inflammatory effect of indomethacin and piroxicam, in the present experiments, can be ascribed to the release of endogenous corticosteroids. This would explain the decreased sensitivity of adrenalectomized animals to the non-steroidal anti-inflammatory drugs used. An additional component, however, seems to be necessary for the full expression of the anti-inflammatory effect of these drugs, since diabetic animals were also less responsive to them. When both components were absent, as in diabetic-adrenalectomized animals, indomethacin and piroxicam were practically devoid of an anti-inflammatory effect.