Blood-brain barrier: endogenous modulation by adrenal-cortical function

Comparison of Tirilazad Mesylate (U-74006F) and Methyl Prednisolone Sodium Succinate Treatments in Experimental Allergic Encephalomyelitis in the Guinea Pig

The effects of the non-glucocortioid 21-aminosteroid, tirilazad mesylate (U-74006F), on MRI and clinical findings in guinea pigs with experimental allergic encephalomyelitis were compared to treatment with methylprednisolone sodium succinate (MPSS). A dose response experiment for U-74006F was performed 1, 3 and 10 mg/kg/day IP on day 0–12 after immunization. Additionally, the 3 mg/kg/day IP dose was extended to 24 and 35 days. MPSS was given in three different protocols at doses ranging from 0.8 to 3.2 mg/kg/day. Abnormalities in T2-weighted images were assessed as measures of edema and inflammation and gadolinium-DTPA enhanced TI-weighted images were used to determine blood-brain barrier integrity. U-74006F improved the clinical status at doses of 3 and 10 mg/kg. For example, maximum clinical score was halved at 10 mg/kg/day (P < 0.01). The presence of gadolinium-DTPA in the parenchyma was also decreased at 3 and 10 mg/kg/day U-74006F although maximum MRI scores were decreased only in the 10 mg/kg U-74006F group. Clinical disease suppression seen with 3 mg/kg treatment on days 0–12 reverted to control at > 24 days of dosing. MPSS treatment considerably worsened the clinical outcome of EAE Mean clinical scores for vehicle and the highest MPSS dose were 0.94 ± 0.66 versus 2.64 ± 1.49 (P < 0.05). The combination of decreased T2-weighted abnormalities, clinical signs and gadolinium-DTPA permeation in the U-74006F treated animals suggested protection of the blood–brain barrier without the severe glucocorticoid effects associated with steroid therapy.

Mineralocorticoid and glucocorticoid receptor-mediated control of genomic responses to stress in the brain

Successful coping with stressful events involves adaptive and cognitive processes in the brain that make the individual more resilient to similar stressors in the future. Stressful events result in the secretion of glucocorticoids (GCs) from the adrenal glands into the blood stream. Early work proved instrumental for developing the concept that these hormones act in the brain to coordinate physiological and behavioral responses to stress through binding to two different GC-binding receptors. Once activated these receptors translocate to the nucleus where they act on target genes to facilitate (or sometimes inhibit) transcription. There are two types of receptors in the brain, the mineralocorticoid receptor (MR), and glucocorticoid receptor (GR). This review summarizes recent work which provides new insights regarding the genomic action of these receptors, both under baseline conditions and following exposure to acute stress. This work is discussed alongside the extensive studies undertaken in this field previously and new, and exciting "big data" studies which have generated a wealth of relevant data. The consequence of these new insights will challenge existing assumptions about the role of MRs and GRs and pave the way for the implementation of novel and improved methodologies to identify the role these corticosteroid receptors have in stress-related behavioral adaptation.

Hormone testing and treatment enters pain care

A number of factors have recently coalesced to bring hormone testing and treatment to the field of pain care. Uncontrolled, severe pain as well as opioid drugs have a profound impact on the endocrine system. Because pain is a potent stressor, it initially causes pituitary, adrenal, and gonadal hormones to elevate in the serum. If severe pain goes uncontrolled for too long, however, hormone levels deplete in the serum. The finding of abnormal (too high or low) serum hormone levels serve as biomarker of endocrinopathies, which helps inform the clinician that enhanced analgesia as well as hormone replacement may be necessary. Adequate, physiologic levels of some specific hormones are necessary for optimal analgesia, neuroprotection, and neurogenesis. Although not a substitute for opioids, some hormone replacements may minimize their use. We know that the central nervous system produces a group of hormones called neurohormones whose natural function is neuroprotection and neurogenesis. Their clinical use in centralized pain states is new, and early reports indicate that they may have considerable benefit for treatment.

The physiologic effects of pain on the endocrine system

Severe pain has profound physiologic effects on the endocrine system. Serum hormone abnormalities may result and these serve as biomarkers for the presence of severe pain and the need to replace hormones to achieve pain control. Initially severe pain causes a hyperarousal of the hypothalamic-pituitary-adrenal system which results in elevated serum hormone levels such as adrenocorticotropin, cortisol, and pregnenolone. If the severe pain does not abate, however, the system cannot maintain its normal hormone production and serum levels of some hormones may drop below normal range. Some hormones are so critical to pain control that a deficiency may enhance pain and retard healing.

Neurovascular damage in experimental allergic encephalomyelitis: a target for pharmacological control

The blood-brain barrier (BBB) is composed of a continuous endothelial layer with pericytes and astrocytes in close proximity to offer homeostatic control to the neurovasculature. The human demyelinating disease multiple sclerosis and the animal counterpart experimental allergic encephalomyelitis (EAE) are characterized by enhanced permeability of the BBB facilitating oedema formation and recruitment of systemically derived inflammatory-type cells into target tissues to mediate eventual myelin loss and neuronal dysfunction. EAE is considered a useful model for examining the pathology which culminates in loss of BBB integrity and the disease is now proving valuable in assessing compounds for efficacy in limiting damage at neurovascular sites. The precise mechanisms culminating in EAE-induced BBB breakdown are unclear although several potentially disruptive mediators have been implicated and have been previously identified as potent effectors of cerebrovascular damage in non-disease related conditions of the central nervous system. The review considers evidence that common mechanisms may mediate cerebrovascular permeability changes irrespective of the initial insult and discusses therapeutic approaches for the control of BBB leakage in the demyelinating diseases.

Ibuprofen prevents altitude illness: a randomized controlled trial for prevention of altitude illness with nonsteroidal anti-inflammatories

STUDY OBJECTIVE

Acute mountain sickness occurs in more than 25% of the tens of millions of people who travel to high altitude each year. Previous studies on chemoprophylaxis with nonsteroidal anti-inflammatory drugs are limited in their ability to determine efficacy. We compare ibuprofen versus placebo in the prevention of acute mountain sickness incidence and severity on ascent from low to high altitude.

METHODS

Healthy adult volunteers living at low altitude were randomized to ibuprofen 600 mg or placebo 3 times daily, starting 6 hours before ascent from 1,240 m (4,100 ft) to 3,810 m (12,570 ft) during July and August 2010 in the White Mountains of California. The main outcome measures were acute mountain sickness incidence and severity, measured by the Lake Louise Questionnaire acute mountain sickness score with a diagnosis of ≥ 3 with headache and 1 other symptom.

RESULTS

Eighty-six participants completed the study; 44 (51%) received ibuprofen and 42 (49%) placebo. There were no differences in demographic characteristics between the 2 groups. Fewer participants in the ibuprofen group (43%) developed acute mountain sickness compared with those receiving placebo (69%) (odds ratio 0.3, 95% confidence interval 0.1 to 0.8; number needed to treat 3.9, 95% confidence interval 2 to 33). The acute mountain sickness severity was higher in the placebo group (4.4 [SD 2.6]) than individuals receiving ibuprofen (3.2 [SD 2.4]) (mean difference 0.9%; 95% confidence interval 0.3% to 3.0%).

CONCLUSION

Compared with placebo, ibuprofen was effective in reducing the incidence of acute mountain sickness.

Ontogeny and the effects of exogenous and endogenous glucocorticoids on tight junction protein expression in ovine cerebral cortices

Maternal glucocorticoid treatment reduces blood-brain permeability early, but not late in fetal development, and pretreatment with glucocorticoids does not affect barrier permeability in newborn lambs. In addition, endogenous increases in plasma cortisol levels are associated with decreases in blood-brain barrier permeability during normal fetal development. Therefore, we tested the hypotheses that development as well as endogenous and exogenous glucocorticoids alters the expression of tight junction proteins in the cerebral cortex of sheep. Cerebral cortices from fetuses at 60%, 70%, and 90% of gestation, newborn and adult sheep were snap frozen after four 6-mg dexamethasone or placebo injections were given over 48-h to the ewes and adult sheep. Lambs were treated similarly with 0.25 mg/kg-dexamethasone or placebo. Tight junction protein expression was measured by Western immunoblot. Claudin-1 was higher (P<0.05) in fetuses at 60% of gestation than in newborn and adult sheep. Claudin-5 was higher at 60% than 70% of gestation, and than in newborn and adult sheep. ZO-1 was higher in newborn than adult sheep. ZO-2 was higher at 90% gestation, in newborn and adult sheep than 60% gestation. Claudin-5 was higher in dexamethasone than placebo-treated lambs, and ZO-2 was higher in fetuses of dexamethasone than placebo-treated ewes at 90% gestation. ZO-2 expression demonstrated a direct correlation with increases in plasma cortisol during fetal development. We conclude that claudin-1, claudin-5, ZO-1, and ZO-2 expression exhibit differential developmental regulation, exogenous glucocorticoids regulate claudin-5 and ZO-2 in vivo at some, but not all ages, and increases in endogenous fetal glucocorticoids are associated with increases in ZO-2 expression, but not with occludin, claudin-1, claudin-5 or ZO-1 expression in ovine cerebral cortices.

Protracted exposure to supraphysiological levels of corticosterone does not cause neuronal loss or damage and protects against kainic acid-induced neurotoxicity in the hippocampus of C57BL/6J mice

High levels of stress or stress hormones have been reported to exacerbate a variety of human disorders of the cardiovascular, gastrointestinal, immune, reproductive, and nervous systems. In rats, high glucocorticoid levels have been reported to cause neuronal death and injury as well as enhance susceptibility to neurotoxic agents and attenuate repair mechanisms; however, the impact of high dosages of CORT in mice has not been fully evaluated. We investigated the ability of supraphysiological levels of CORT to cause hippocampal neuronal death, and to modulate the neurotoxicity of kainic acid (KA) in male C57BL/6J mice. Timed-release CORT pellets (10, 35, 100 mg/21 d) were implanted subcutaneously in the back of mice, and the sustained release of glucocorticoid caused involution of the thymus and decreased the weight of the spleen. Kainic acid caused stage 1 seizures that were unaffected by CORT; however, steroid treatment decreased KA-associated mortality. Little neuronal damage was detected by the cupric-silver neurodegeneration stain. Neurotoxicity caused by an intraperitoneal injection of 25mg/kg KA was attenuated by seven days of CORT pre-treatment. The KA-induced increase in cupric-silver staining, reactive gliosis, microglial activation, and blood-brain barrier disruption was attenuated indicating neuroprotection. Our data indicate supraphysiological levels of CORT do not cause neuronal death or injury in hippocampus of C57BL/6J mice and provide neuroprotection against KA-induced neural damage.

Corticosteroids delay remyelination of experimental demyelination in the rodent central nervous system

High dose corticosteroid (CS) administration is a common mode of therapy in treatment of acute relapses in multiple sclerosis (MS) but the effects of CS on remyelination and the cellular mechanisms mediating this repair process are controversial. We have examined CS effects on repair of toxin-induced demyelinating lesions in the adult rat spinal cord. Corticosteroids reduced the extent of oligodendrocyte remyelination at 1 month post lesion (whereas Schwann-cell mediated repair was unaffected). However, CS did not cause permanent impairment of remyelination as lesions were fully remyelinated at 2 months after cessation of treatment. The delay in oligodendrocyte mediated repair could be attributed to inhibition of differentiation of oligodendrocyte progenitor cells (OPCs) into oligodendrocytes, with no effect of CS treatment observed on OPC colonisation of the lesions. No differences were observed in animals treated with methylprednisolone succinate alone or with a subsequent prednisone taper indicating that CS effects occur at an early stage of repair. The potential consequences of delayed remyelination in inflammatory lesions are discussed.

Glucocorticoid receptor–nitric oxide crosstalk and vulnerability to experimental parkinsonism: pivotal role for glia–neuron interactions

Inflammation and oxidative stress have been closely associated with the pathogenesis of neurodegenerative disorders, including Parkinson's disease (PD). The expression of inducible nitric oxide synthase (iNOS) in astrocytes and microglia and the production of large amounts of nitric oxide (NO) are thought to contribute to dopaminergic neuron demise. Increasing evidence, however, indicates that activated astroglial cells play key roles in neuroprotection and can promote recovery of CNS functions. Endogenous glucocorticoids (GCs) via glucocorticoid receptors (GRs) exert potent anti-inflammatory and immunosuppressive effects and are key players in protecting the brain against stimulation of innate immunity. Here we review our work showing that exposure to a dysfunctional GR from early embryonic life in transgenic (Tg) mice expressing GR antisense RNA represents a key vulnerability factor in the response of nigrostriatal dopaminergic neurons to the neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), and further report that exacerbation of dopaminergic neurotoxicity with no recovery is determined by failure of astroglia to exert neuroprotective effects. Aberrant iNOS gene expression and increased glia vulnerability to cell death characterized the response of GR-deficient mice to stimulation of innate immunity. More importantly, GR-deficient glial cells failed to protect fetal dopaminergic neurons against oxidative stress-induces cell death, whereas wild-type glia afforded neuroprotection. Thus, lack of iNOS/NO regulation by GCs can program an aberrant GR-NO crosstalk in turn responsible for loss of astroglia neuroprotective function in response to stimulation of innate immunity, pointing to glia and efficient GR-NO dialogue as pivotal factors orchestrating neuroprotection in experimental parkinsonism.

The pharmacokinetics of erythropoietin in the cerebrospinal fluid after intravenous administration of recombinant human erythropoietin

OBJECTIVES

Erythropoietin (EPO) was originally described as a regulator of erythropoiesis. Recently, synthesis of EPO and expression of the EPO receptor (EPO-R) have been reported for the central nervous system (CNS). The potential use of EPO to prevent or reduce CNS injury and the paucity of information regarding its entry into the human CNS led us to examine the pharmacokinetics (PK) of recombinant human EPO (r-HuEPO) in the serum and cerebrospinal fluid (CSF).

METHODS

Four patients with Ommaya reservoirs were enrolled to facilitate serial CSF sampling. R-HuEPO was given intravenously (IV) in single doses of 40,000 IU or 1,500 IU/kg and in multiple doses of 40,000 IU daily for 3 days.

RESULTS

The EPO concentrations in the CSF increased after a period of slow equilibration. Linear first-order distribution kinetics were observed for serum and CSF. The concentration of EPO in the CSF was proportional to the serum concentration of EPO and the permeability of the blood-brain barrier (BBB), as determined by the albumin quotient (QA=[albumin] CSF/[albumin] serum). A rise in the CSF concentration was seen as early as 3 h after IV administration. Peak levels (C(max)) were reached between 9 h and 24 h. After a single dose of 1,500 IU/kg, the Cmax in the CSF ranged from 11 mIU/ml to 40 mIU/ml, and the ratios of CSF/serum Cmax ranged from 3.6x10-4 to 10.2x10-4. The terminal half-life (t1/2) values of EPO in serum and CSF were similar. The t(1/2) of r-HuEPO in the CSF ranged from 25.6 h to 35.5 h after a single dose of 1,500 IU/l. Using these parameters a PK model was generated that predicts the concentration-time profile of EPO in the CSF.

CONCLUSIONS

We report that r-HuEPO can cross the human BBB and describe for the first time the PK of EPO in the CSF after IV administration. Our data suggest that the concentration-time profile of EPO in the CSF can be predicted for individual patients if the serum concentration of EPO and the Q(A) are known. This information may be useful in the design of clinical trials to explore the potential therapeutic effects of EPO during CNS injury.

Normalization of serum cortisol concentration with opioid treatment of severe chronic pain

Serum cortisol concentrations may be altered in severe, chronic pain due to excess stimulation of the hypothalamic-pituitary-adrenal axis. Among 40 consecutive patients with severe, chronic pain 26 (65.0%) demonstrated abnormal serum cortisol concentration. After 90 days of treatment, only 7 (17.5%; p<0.01) continued to show abnormal serum cortisol concentration indicating that serum cortisol and other serologic abnormalities may serve as biologic markers of severe, chronic pain.

Reversal of cycloheximide-induced memory disruption by AIT-082 (Neotrofin) is modulated by, but not dependent on, adrenal hormones

RATIONALE

AIT-082 (Neotrofin), a hypoxanthine derivative, has been shown to improve memory in both animals and humans. In animals, adrenal hormones modulate the efficacy of many memory-enhancing compounds, including piracetam and tacrine (Cognex).

OBJECTIVE

To investigate the role of adrenal hormones in the memory-enhancing action of AIT-082.

METHODS

Plasma levels of adrenal hormones (corticosterone and aldosterone) in mice were significantly reduced by surgical or chemical (aminoglutethimide) adrenalectomy or significantly elevated by oral administration of corticosterone. The effects of these hormone level manipulations on the memory-enhancing activity of AIT-082 and piracetam were evaluated using a cycloheximide-induced amnesia/passive avoidance model.

RESULTS

As previously reported by others, the memory enhancing action of piracetam was abolished by adrenalectomy. In contrast, the memory enhancement by 60 mg/kg AIT-082 (IP) was unaffected. However, a sub-threshold dose of AIT-082 (0.1 mg/kg, IP) that did not improve memory in control animals did improve memory in adrenalectomized animals. These data suggested that, similar to piracetam and tacrine, the memory enhancing action of AIT-082 might be inhibited by high levels of adrenal hormones. As expected, corticosterone (30 and 100 mg/kg) inhibited the action of piracetam, however no dose up to 100 mg/kg corticosterone inhibited the activity of AIT-082.

CONCLUSIONS

These data suggest that while AIT-082 function is not dependent on adrenal hormones, it is modulated by them. That memory enhancement by AIT-082 was not inhibited by high plasma corticosterone levels may have positive implications for its clinical utility, given that many Alzheimer's disease patients have elevated plasma cortisol levels.

Penetration of endogenous steroid hormones corticosterone, cortisol, aldosterone and progesterone into the brain is enhanced in mice deficient for both mdr1a and mdr1b P-glycoproteins

Numerous investigations have confirmed an important role for multidrug-resistance gene 1-type P-glycoproteins (MDR1-type P-gps) in the blood-brain barrier, protecting the brain against the accumulation of a wide range of toxic xenobiotics and drugs. Several studies have provided evidence in vitro that certain steroid hormones are transported by MDR1-type P-gps; however, the question of whether this might also apply to the situation in vivo still remained to be determined. We used mice deficient for both murine mdr1a and mdr1b P-gps [mdr1a/1b(-/-)] to determine the uptake of [3H]-cortisol, [3H]-corticosterone, [3H]-aldosterone and [3H]-progesterone into the plasma, brain, testes, liver, spleen, pituitary and adrenal glands. We provide evidence that the access of the endogenous steroid hormones corticosterone, cortisol and aldosterone is regulated by MDR1-type P-gps in vivo. As peripherally administered steroid hormones accumulate in the brain of mice deficient for MDR1-type P-gps, mdr1a/1b proteins are likely to transport these hormones out of the brain, providing a kinetic barrier to their entry. Intracerebral progesterone concentrations are influenced by MDR1-type P-gp function as well; however, the effects are only small. In addition, all four endogenous glucocorticoid hormones accumulated in the testes of mdr1a/1b(-/-) mice. Our findings underline the importance of MDR1-type P-gps as an endogenous barrier system controlling the access of endogenous steroid hormones at the blood-brain barrier to maintain homeostatic control and to protect central nervous system neurones.

Exposure to a dysfunctional glucocorticoid receptor from early embryonic life programs the resistance to experimental autoimmune encephalomyelitis via nitric oxide-induced immunosuppression

Glucocorticoid (GC) hormones play a central role in the bidirectional communication between the neuroendocrine and the immune systems and exert, via GC receptors (GR), potent immunosuppressive and anti-inflammatory effects. In this study, we report that GR deficiency of transgenic mice expressing GR antisense RNA from early embryonic life has a dramatic impact in programming the susceptibility to experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis. GR deficiency renders mice resistant to myelin oligodendrocyte glycoprotein-induced EAE, and such mice do not develop clinical or histological signs of disease compared with EAE-susceptible wild-type mice. Resistance to EAE in GR-deficient mice is associated not with endogenous GC levels, but with a significant reduction in spleen and lymph node cell proliferation. The use of NO inhibitors in vitro indicates that NO is the candidate immunosuppressor molecule. GR-deficient mice develop 3- to 6-fold higher nitrite levels in the periphery and are resistant to NO inhibition by GCs. Specific inhibition of NO production in vivo by treatment with the inducible NO synthase inhibitor, L-N(6)-(1-iminoethyl)-lysine, suppressed circulating nitrites, increased myelin oligodendrocyte glycoprotein-specific cell proliferation, and rendered GR-deficient mice susceptible to EAE. Thus, life-long GR deficiency triggers inducible NO synthase induction and NO generation with consequent down-regulation of effector cell proliferation. These findings identify a novel link among GR, NO, and EAE susceptibility and highlight NO as critical signaling molecule in bidirectional communication between the hypothalamic-pituitary-adrenocortical axis and the immune system.

Stress, the immune system and vulnerability to degenerative disorders of the central nervous system in transgenic mice expressing glucocorticoid receptor antisense RNA

Current research evidence suggests that interactions between genetic and environmental factors contribute to modulate the susceptibility to degenerative disorders, including inflammatory and autoimmune diseases of the central nervous system (CNS). In this context, bidirectional communication between the neuroendocrine and immune systems during ontogeny plays a pivotal role in programming the development of neuroendocrine and immune responses in adult life, thereby influencing the predisposition to several disease entities. Glucocorticoids (GCs), the end products of the hypothalamic-pituitary-adrenocortical (HPA) axis, gender and signals generated by hypothalamic-pituitary-gonadal (HPG) axis are major players coordinating the development of immune system function and exerting powerful effects in the susceptibility to autoimmune disorders, including experimental autoimmune encephalomyelitis (EAE), the experimental model for multiple sclerosis (MS). In particular, GCs exert their beneficial immunosuppressive and anti-inflammatory effects in inflammatory disorders of the CNS, after binding to their cytoplasmic receptors (GRs). Here we review our work using transgenic (Tg) mice with a dysfunctional GR from early embryonic life on programming vulnerability to EAE. The GR-deficiency of these Tg mice confers resistance to active EAE induction. The interplay between GCs, proinflammatory mediators, gender and EAE is summarized. On the basis of our data, it does appear that exposure to a defective GR through development programs major changes in endogenous neuroendocrine and immune mechanisms controlling the vulnerability to EAE. These studies highlight the plasticity of the HPA-immune axis and its pharmacological manipulation in autoimmune diseases of the CNS.

Effects of postnatal dexamethasone on blood-brain barrier permeability and brain water content in newborn lambs

We showed that antenatal corticosteroids reduced blood-brain barrier permeability in fetuses at 60 and 80%, but not 90% of gestation, and decreased brain water content in fetuses. Our objective was to examine the effects of postnatal corticosteroids on regional blood-brain barrier permeability and brain water content in newborn lambs. Three dexamethasone treatment groups were studied in 3- to 5-day-old lambs. A 0.01 mg/kg dose was selected to estimate the amount of dexamethasone that might have reached fetuses via antenatal treatment of ewes in our previous studies. The other doses (0.25 and 0.5 mg/kg) were chosen to approximate those used clinically to treat infants with bronchopulmonary dysplasia. Lambs were randomly assigned to receive four intramuscular injections of dexamethasone or placebo given 12 h apart on days 3 and 4 of age. Blood-brain barrier function was measured with the blood-to-brain transfer constant (K(i)) to alpha-aminoisobutyric acid, brain plasma volume was measured with polyethylene glycol for the calculation of K(i,) and brain water was measured by wet-to-dry tissue weights. Postnatal treatment with corticosteroids did not reduce barrier permeability in newborn lambs. Brain blood volume was higher in the 0.25 and 0.5 mg/kg dose dexamethasone groups than in the placebo group. Brain water content did not differ among the groups. We conclude that postnatal treatment with corticosteroids did not reduce regional blood-brain barrier permeability or brain water content but increased the brain plasma volume in newborn lambs. These findings are consistent with our previous work indicating that barrier permeability is responsive to corticosteroids at 60 and 80% of gestation and brain water regulation at 60% of gestation, but not in near-term fetuses or newborn lambs.

Exogenous and endogenous corticosteroids modulate blood-brain barrier development in the ovine fetus

We previously reported decreases in blood-brain barrier permeability in the ovine fetus at 80% of gestation after antenatal corticosteroids and shown that permeability is not reduced in newborn lambs after postnatal corticosteroids. We now test the hypotheses that exogenous antenatal corticosteroids decrease blood-brain barrier permeability at 60% but not 90% of gestation in ovine fetuses and that endogenous increases in plasma cortisol concentrations are associated with ontogenic decreases in barrier permeability during gestation. Chronically instrumented ovine fetuses were studied 12 h after the last of four 6-mg dexamethasone or placebo injections were given 12 h apart over 48 h to ewes. Fetuses at 80% of gestation from placebo-treated ewes studied under the same protocol were also included. Blood-brain barrier function was quantified with the blood-to-brain transfer constant (K(i)) to alpha-aminoisobutyric acid. K(i) values were lower in cerebral cortex, caudate nucleus, hippocampus, superior colliculus, thalamus, medulla, and cervical spinal cord in fetuses of dexamethasone- than placebo-treated ewes at 60% but not 90% of gestation. Regional brain K(i) values demonstrated inverse correlations with increases in gestation and plasma cortisol concentrations in most brain regions. We conclude that maternal treatment with exogenous corticosteroids was associated with decreases in blood-brain barrier permeability at 60% but not 90% of gestation and that increases in gestation and endogenous cortisol concentrations were associated with ontogenic decreases in barrier permeability during fetal development.

The detection and quantitation of inflammation in the central nervous system during experimental allergic encephalomyelitis using the radiopharmaceutical 99mTc-RP128

RP128 is a novel agent which readily chelates 99mTc to form a radiopharmaceutical which binds in vivo to the tuftsin receptor located specifically on neutrophils and monocyte-macrophages, therefore removing the need for in vitro cell labelling prior to intravenous administration. We have assessed the ability of 99mTc-RP128 to detect central nervous system (CNS) inflammation in experimental allergic encephalomyelitis (EAE), an animal model of the human disease multiple sclerosis. The radiopharmaceutical was recorded at significantly increased levels in all EAE diseased CNS tissues, compared to normal and control samples, at 0.5, 1 and 3 h post-injection using a dual radioisotope technique to correct for non-extravasated tracer (P<0.05). Moreover, extravascular accumulation of the agent could be clearly demonstrated in inflammatory tissues with minimal loss of sensitivity when the secondary isotopic correction for blood volume was omitted. In addition, 99mTc-RP128 successfully monitored glucocorticoid suppression of inflammation (P<0.05), recording a typical dose-response to increasing steroid concentration. Clearly, 99mTc-RP128 can quantitatively detect CNS inflammation and assess responses to therapy indicating potential value as an imaging agent both clinically and as a research aid. Furthermore, the rapid in vivo labelling by 99mTc-RP128 of specific inflammatory cells combined with the ability to monitor the progress of anti-inflammatory therapeutics may recommend the agent for use in a variety of inflammatory conditions.

Ecosystems supporting clusters of sporadic TSEs demonstrate excesses of the radical-generating divalent cation manganese and deficiencies of antioxidant co factors Cu, Se, Fe, Zn. Does a foreign cation substitution at prion protein's Cu domain initiate TSE?

Analyses of food chains supporting isolated clusters of sporadic TSEs (CWD in N Colorado, scrapie in Iceland, CJD in Slovakia) demonstrate a consistent 2 1/2+ fold greater concentration of the pro-oxidant divalent cation, manganese (Mn), in relation to normal levels recorded in adjoining TSE-free localities. Deficiencies of the antioxidant co factors Cu/Se/Zn/Fe and Mg, P and Na were also consistently recorded in TSE foodchains. Similarities between the clinical/pathological profile of TSEs and Mn delayed psycho-neurotoxicity in miners are cited, and a novel theory generated which suggests that sporadic TSE results from early life dependence of TSE susceptible genotypes on ecosystems characterised by this specific pattern of mineral imbalance. Low Cu/Fe induces an excessive absorption of Mn in ruminants and an increased oxidation of Mn2+ into its pro oxidant species, Mn3+, which accumulates in mitochondria of CNS astrocytes in Mn SOD deficient genotypes. Deficiencies of scavenger co factors Cu/Zn/Se/Fe in the CNS permits Mn3+ initiated chain reactions of auto-oxidant mediated neuronal degeneration to proliferate, which, in turn, up-regulates the expression of the Cu-metalloprotein, prion protein (PrP). Once the rate of PrP turnover and its demand for Cu exceeds the already depleted supply of Cu within the CNS, PrP can no longer bind sufficient Cu to maintain its conformation. Mn3+ substitutes at the vacated Cu domain on PrP, thus priming up a latent capacity for lethal auto-oxidative activity to be carried along with PrP like a 'trojan horse'; where Mn 3+ serves as the integral 'infectious' transmissible component of the misfolded PrP-cation complex. The Mn overactivation of concanavalin A binding to glycoprotein and Mn-initiated autoxidation results in a diverse pathological profile involving receptor capping, aggregation/modification of CNS membrane/cytoskeletal proteins. TSE ensues. The BSE/nv CJD strain entails a 'synthetic' induction of the same CNS mineral disturbance, where 'in utero' exposure to Cu-chelating insecticides/Mn supplements accelerates the onset of a more virulent 'strain' of adolescent TSE.

Antenatal steroids decrease blood-brain barrier permeability in the ovine fetus

Antenatal corticosteroid therapy reduces the incidence of intraventricular hemorrhage in premature infants. Enhanced microvascular integrity might provide protection against intraventricular hemorrhage. In the adult, there is evidence to suggest that the blood-brain barrier may be under hormonal control. We hypothesized that antenatal corticosteroids decrease blood-brain barrier permeability in the preterm ovine fetus. Chronically instrumented 120-day-gestation fetuses were studied 12 h after the last of four 6-mg dexamethasone (n = 5) or placebo (n = 6) injections had been given over 48 h to the ewes. Blood-brain barrier function was quantified with the blood-to-brain transfer constant (Ki) for alpha-aminoisobutyric acid (AIB). Ki was significantly lower across brain regions in the fetuses of ewes that received antenatal dexamethasone compared with placebo (ANOVA; interaction, F = 2.54, P < 0.004). In fetuses of dexamethasone- and placebo-treated ewes, Ki (microliter . g brain wt-1. min-1, mean +/- SD) was, respectively, 2.43 +/- 0.27 vs. 3.41 +/- 0.74 in the cortex, 4.46 +/- 0.49 vs. 5.29 +/- 0.85 in the cerebellum, and 3.70 +/- 0.49 vs. 5.11 +/- 0.70 in the medulla. We conclude that antenatal treatment with corticosteroids reduces blood-brain permeability in the ovine fetus.

Inhibition of inducible nitric oxide synthase prevents myocardial and systemic vascular barrier dysfunction during early cardiac allograft rejection

NO is produced during cardiac allograft rejection by expression of inducible NO synthase (iNOS) in the rejecting heart. Recent evidence indicates that NO modulates vascular permeability under both physiological and pathophysiological conditions. The present study explored the effects of early acute cardiac allograft rejection, and specifically the effects of NO, on myocardial and systemic vascular barrier function using a quantitative double-tracer permeation method in a rat cardiac transplant model. Early allograft rejection increased albumin permeation twofold to fivefold in the allograft heart and systemic vasculature (brain, lung, sciatic nerve, diaphragm, retina, muscle, kidney, and uvea) compared with isografts and controls. There were no detectable differences in regional blood flow or hemodynamics, suggesting that increased albumin permeation resulted from increased vascular permeability. iNOS mRNA was expressed in the allograft heart and native lung and was associated with increased serum nitrite/nitrate levels. iNOS inhibition with aminoguanidine prevented or attenuated allograft heart and systemic vascular barrier dysfunction and reduced allograft serum nitrite/nitrate levels to isograft values. Aminoguanidine did not affect the mild histological changes of rejection present in allografts. These data demonstrate the novel observations that (1) endothelial barrier function is compromised in the systemic vasculature, particularly in the brain, remote from the site of allograft rejection; (2) allograft vascular barrier dysfunction is associated with increased NO production and iNOS mRNA expression in the affected tissues (eg, native lung and grafted heart); and (3) inhibition of NO production by iNOS prevents vascular barrier dysfunction in the allograft heart and systemic vasculature.

Differential effects of glucocorticoids on human auditory perception

It is assumed that glucocorticoids and mineralocorticoids, the hormones produced by the adrenal cortex, act as modulators of central nervous functions in addition to their well-known role in endocrine stress responses. More specifically, it has been suggested that adrenal corticoids cause changes in sensory thresholds. In two double-blind crossover studies we evaluated auditory perception in healthy volunteers after treatment with hydrocortisone, dexamethasone, and the respective placebos. Stapedial reflexes, pure tone and speech audiograms, and brainstem electric response audiometry served as the dependent variables. As circadian changes in the density and occupancy of the brain corticosteroid receptors have been postulated, we performed Study I in the morning and Study II in the evening. Treatment effects clearly varied with time of day. A differential effect of the two corticoids occurred on contralateral stapedial reflexes. These results parallel results obtained with gustatory stimuli, and suggest that glucocorticoids modulate sensory perception across modalities.

Inhibition of blood-brain barrier disruption in experimental allergic encephalomyelitis by short-term therapy with dexamethasone or cyclosporin A

Double radioisotope measurement of neurovascular integrity in Lewis rats inoculated for experimental allergic encephalomyelitis (EAE) showed abnormal elevation of albumin extravasation in the cerebellum, medulla-pons and cervical spinal cord at the time of clinical manifestation. Therapeutically administered dexamethasone (Dex) (0.1-1 mg/kg body weight) or cyclosporin A (CsA) (25-75 mg/kg body weight) dose-dependently reduced albumin movement across the blood-brain barrier (BBB). Dex at a dose of 1 mg/kg completely suppressed abnormal BBB permeability in all tissues (P < or = 0.001), while CsA at the highest dose of 75 mg/kg achieved highly significant (P < or = 0.001), but not complete, suppression of aberrant barrier leakage in the areas studied. The implications of these findings to possible drug action at the immunocompromised cerebrovasculature are discussed.

Neoplastic and pharmacological influence on the permeability of an in vitro blood-brain barrier

The authors investigated the effects of glioma cells and pharmacological agents on the permeability of an in vitro blood-brain barrier (BBB) to determine the following: 1) whether malignant glia increase endothelial cell permeability; 2) how glucocorticoids affect endothelial cell permeability in the presence and absence of malignant glia; and 3) whether inhibiting phospholipase A2, the enzyme that releases arachidonic acid from membrane phospholipids, would reduce any malignant glioma-induced increase in endothelial cell permeability. Primary cultures of rat brain capillary endothelium were grown on porous membranes; below the membrane, C6, 9L rat glioma. T98G human glioblastoma, or no cells (control) were cocultured. Dexamethasone (0.1 microM), bromophenacyl bromide (1.0 microM), a phospholipase A2 inhibitor, or nothing was added to culture media 72 hours prior to assaying the rat brain capillary endothelium permeability. Permeability was measured as the flux of radiolabeled sucrose across the rat brain capillary endothelium monolayer and then calculated as an effective permeability coefficient (Pe). When neither dexamethasone nor bromophenacyl bromide was present, C6 cells reduced the Pe significantly (p < 0.05), whereas 9L and T98G cells increased Pe significantly (p < 0.05) relative to rat brain capillary endothelium only (control). Dexamethasone reduced Pe significantly for all cell preparations (p < 0.05). The 9L and T98G cell preparations coincubated with dexamethasone had the lowest Pe of all cell preparations. The Pe was not affected in any cell preparation by coincubation with bromophenacyl bromide (p > 0.45). These in vitro BBB experiments showed that: 1) malignant glia, such as 9L and T98G cells, increase Pe whereas C6 cells probably provide an astrocytic influence by reducing Pe; 2) dexamethasone provided significant BBB "tightening" effects both in the presence and absence of glioma cells; 3) the in vivo BBB is actively made more permeable by malignant glia and not simply because of a lack of astrocytic induction; 4) tumor or endothelial phospholipase A2 activity is probably not responsible for glioma-induced increased in BBB permeability; and 5) this model is useful for testing potential agents for BBB protection and for studying the pathophysiology of tumor-induced BBB disruption.

Regulation of 5-HT receptors by corticosteroids: where do we stand?

Twenty five years ago, experimental procedures such as adrenalectomy and corticosteroid administration (to intact rats) allowed the recognition of direct and indirect controls of central 5-HT synthesis rate by corticosteroids. These effects indicated that the activity of the hypothalamo-pituitary-adrenal (HPA) axis, whether under basal conditions or during stress, is endowed with a modulatory action upon serotonergic neurons. Nowadays, in situ hybridisation, in vitro autoradiography, and radioligand binding on the one hand, and electrophysiological, behavioural, and neuroendocrinological responses on the other hand, are tools that allow the analysis of direct corticosteroid effects upon 5-HT receptors. Among the dozen of 5-HT receptors identified so far, four receptors (namely the 5-HT1A, 5-HT1B, 5-HT2A, and 5-HT2C receptors)--and the 5-HT uptake system--have been the focus of studies aimed at detecting corticosteroid modulatory effects. The results that are reviewed herein indicate that hippocampal 5-HT1A receptors are under the tonic inhibitory control of corticosterone. This control is directly exerted at the level of the 5-HT1A receptor gene, essentially through mineralocorticoid receptors; as well, electrophysiological findings bring support for an additional modulation of hippocampal 5-HT1A receptor-mediated functions by indirect (ie 5-HT1A receptor gene-independent) genomic actions of corticosteroids. In keeping with the respective effects of stressful stimuli and psychotropic drugs upon the HPA axis and central serotonergic systems, it is likely that these corticosteroid-5-HT1A receptor interactions in the hippocampus have consequences in the pathophysiology of mood disorders. However, because the data regarding a corticosteroid control of other 5-HT receptors are either scarce and contradictory (eg 5-HT1B, 5-HT2A, 5-HT2C receptors and 5-HT uptake systems) or lacking, it is at the present time unknown whether corticosteroids exert other effects on 5-HT receptor-mediated functions, including those related to homeostasis.

Induction of muricidal behavior by ACTH or adrenalectomy in young male Wistar rats

ACTH administered IP induces a muricidal behavior in 52% of male Wistar rats that do not express it before; such behavior is also observed spontaneously in 68% of adrenalectomized animals. This change in behavior is characterized by an exceptionally long duration (several months in some animals), and by its prevention by previous or substitutive treatments with dexamethasone. Data obtained using hypophysectomized or adrenalectomized animals with or without ACTH treatments suggest that the muricidal-inducing effect of ACTH might have, at least partially, a central origin.

The use of intracerebral microdialysis to determine changes in blood-brain barrier transport characteristics

The aim of this study was to determine whether changes in the transport of drugs into the brain could be determined by in vivo intracerebral microdialysis. Atenolol was used as a model drug to determine blood-brain barrier (BBB) transport characteristics. In rats, unilateral opening of the blood-brain barrier was achieved by infusion of hyperosmolar mannitol (25%, w/v) into the left internal carotid artery. BBB transport, expressed as the ratio of the area under the curve (AUC) of atenolol in brain extracellular fluid over plasma, was three times higher for the mannitol treated hemisphere as compared with the contralateral brain or after infusion of saline, being (mean +/- SEM) 0.094 +/- 0.024 (n = 16), 0.029 +/- 0.007 (n = 12) and 0.030 +/- 0.009 (n = 12) respectively. Further evaluation of the data indicated that for experiments performed in the morning the mannitol infusion had little effect on the extent of transport of atenolol into the brain, while in the afternoon BBB transport was about 10-fold higher than in the contralateral and saline group. The mean "afternoon" ratios +/- SEM were 0.155 +/- 0.038 (n = 8), 0.012 +/- 0.003 (n = 6) and 0.018 +/- 0.006 (n = 6) respectively. It is concluded that intracerebral microdialysis is capable of revealing changes in BBB transport and regional and time-dependent differences in drug levels can be demonstrated with the use of this technique.

Hierarchical cortical control of neuroimmunomodulatory pathways

The central nervous system and the immune system are both stimulus response systems with sophisticated memories mediating defence and adaptation to external and internal threats. There is mounting evidence that these two systems share their information in a bidirectional flow of cytokines, steroids, and neuropeptides. This review examines the influence of higher cognitive centres on immunity and highlights the central role played by the hypothalamus in enabling these two systems to function as an integrated unit to maintain homeostasis. The search for novel compounds that are capable of enhancing immunity by regulating these brain-immune feedback loops offers one of the most exciting areas for future neurobiological research.

Adrenalectomy-induced increase of brain protein synthesis is antagonized by corticosterone replacements in free-moving rats

The autoradiographic method with L-[35S]-methionine was used to determine whether changes in glucocorticoid circulating levels were associated with changes in local rates of protein synthesis in rat brain. Chronic bilateral adrenalectomy induced an increase of methionine incorporation rates into proteins in 60 of the 62 brain regions examined (mean effect, +50%). This effect was confirmed biochemically and quantified by correcting for the relative contribution of methionine derived from protein degradation to the precursor pool for protein synthesis in the whole brain. Acute or chronic administration of corticosterone, at doses that normalize basal levels of adrenocorticotrophic hormone, reversed or prevented the adrenalectomy-induced increase of protein synthesis in most regions. However, in nearly all the regions studied (59 of 62), acute corticosterone administration to sham-operated rats did not change the apparent rate of protein synthesis. These results demonstrate that glucocorticoids exert a generalized inhibitory action on brain protein synthesis, because the stimulatory and persistent effect of adrenalectomy on protein synthesis was antagonized by corticosterone replacements at physiological doses. Thus, the regulation of overall brain protein synthesis by glucocorticoids emphasizes the role of neuroendocrine events on long-term neurochemical processes.

Suppression of experimental autoimmune encephalomyelitis by restraint stress: sex differences

We have recently reported that female Lewis rats exhibit significantly higher basal circadian levels of corticosterone (Cort) than male Lewis rats. The studies reported here were designed to explore whether male and female Lewis rats demonstrate a differential suppression of experimental autoimmune encephalomyelitis (EAE) following exposure to an identical regimen of repetitive restraint stress. Rats were restrained for 1 or 9 h/day beginning 5 days before myelin basic protein (MBP) challenge and extending through the recovery period (18 days post challenge). Both clinical signs and histopathological changes of EAE were more significantly suppressed in 9-h-stressed females relative to male Lewis rats. Investigation of the mechanism underlying the stress-induced suppression of EAE revealed that restraint stress did not alter the clinical course of EAE in rats challenged with MBP 68-88 encephalitogenic peptide, suggesting that restraint stress may affect processing and/or presentation of the MBP molecule. Stressed rats exhibited decreased interleukin-2 and interferon gamma production, and the frequency of MBP-reactive lymphocytes was reduced in comparison to non-stressed rats. Finally, repetitive restraint stress had no effect on blood-spinal cord permeability during EAE. The results presented here underscore the importance of such experimental variables as sex, strain, time of day, and the kinetics of immune response development.

Nicotine and its major metabolite cotinine have different effects on aldosterone and prolactin serum levels in the normal male rat

Nicotine (0.01-1.0 mg/kg, i.p.) or cotinine (0.003-1.0 mg/kg, i.p.) treatment was administered to Sprague-Dawley male rats. The time-effect curves (5, 10, 30, 60 and 180 min) were analyzed. Nicotine dose-dependently increased blood aldosterone and corticosterone levels with a peak effect 10 min after the intraperitoneal injection. Nicotine treatment weakly decreased serum levels of aldosterone at 2 h, possibly as a consequence of nicotine metabolising to cotinine, resulting in higher serum levels of cotinine than nicotine. Cotinine dose-dependently reduced serum aldosterone levels, an effect which became more marked with time, leaving plasma corticosterone unchanged. Nicotine dose-dependently increased serum prolactin levels at 5 and 10 min following treatment, an effect which had diminished at 30 min. Cotinine dose-dependently reduced serum prolactin levels at 5 min followed by a dose-dependent increase at 10 min after which a dose-dependent reduction was again found after 30 min post treatment. In conclusion, acute nicotine and cotinine treatment produced opposite effects on aldosterone and prolactin serum levels. The prolonged effect of cotinine on aldosterone levels may be involved in changes in brain function, and may be connected to the development of withdrawal effects after stopping cigarette smoking. As reported by other investigators, nicotine produced enhanced plasma corticosterone levels while cotinine treatment was ineffective. Since cotinine induced marked changes in serum prolactin levels while leaving LH levels unchanged, it seems plausible that cotinine affects neuroendocrine regulation via mechanisms not primarily related to circulatory effects. Thus, an action at the median eminence--pituitary level seems likely.

Hormonal influence on the permeability of the blood-brain barrier: effect of an analog of adrenocorticotropic hormone, beta 1-24 corticotrophin

Regional unidirectional transport of alpha-aminoisobutyric acid (AIB) (mol. wt.: 104) and sucrose (mol wt.: 342) which have a low permeability across the intact endothelium was investigated in brain of rats either treated with synacthène: an analog of ACTH, tetracosactide retard (beta-1-24 corticotrophin) or in brain of placebo-treated controls. Three days treatment with synacthène, reduced the rate of influx of AIB and sucrose in most of the brain regions studied especially in thalamus, hypothalamus, cortex, and caudate nucleus without affecting the vascular compartment. The brainstem, cerebellum and white matter were less affected. These experimental findings may suggest that ACTH exhibits significant influence on hormonal regulation of blood-brain barrier permeability. Thereby such a regulation may involve the entry of polar compounds into the CNS and may influence the central effects of diffusion-limited drugs.

Physiopharmacological interactions between stress hormones and central serotonergic systems

The present review tries to delineate some mechanisms through which the sympathetic nervous system (SNS) and the hypothalamo-pituitary-adrenal (HPA) interact with central serotonergic systems. The recent progress in 5-hydroxytryptamine (5-HT) receptor pharmacology has helped to define the means by which central serotonergic activity may alter the respective activities of the SNS (sympathetic nerves and adrenomedulla) and of the HPA axis. These pharmacological findings have also helped to characterize the differential effects of central 5-HT upon different branches of the SNS and the numerous sites at which 5-HT exerts stimulatory influences upon the HPA axis. Although relevant to stress-related neuroendocrinology, the extent to which these interactions are involved in the antidepressant/anxiolytic properties of some serotonergic agents still remains to be clarified. Beside these findings, there is also abundant evidence for a tight control of central serotonergic systems by stress hormones. Activation of the SNS increases, by numerous means, central availability of tryptophan, whereas glucocorticoids exert differential actions upon the intra- and the extraneuronal regulation of 5-HT function. Actually, a significant number of these mechanisms is involved in the maintenance of homeostasis during stressful events, thereby conferring to these mechanisms a key role in adaptation processes.

Correlation of myelin basic protein-like material in cerebrospinal fluid of multiple sclerosis patients with their response to glucocorticoid treatment

Predictors and laboratory correlates of the response of patients with multiple sclerosis to glucocorticoids are not well defined. Our study was undertaken to determine if the levels of myelin basic protein (MBP)-like material in cerebrospinal fluid (CSF) might indicate which patients with multiple sclerosis would show a short-term (5 day) or intermediate-term (40 day) improvement of at least a full-grade Kurtzke disability score after initiating treatment with glucocorticoids. A total of 62 patients received 71 courses of treatment consisting of 5 days of intravenous methylprednisolone (500 mg per day) usually followed by a 4-week tapering dose of oral prednisone. CSF was obtained before initiation of treatment and analyzed for MBP-like material by radioimmunoassay. Results were analyzed by chi 2 tests of association and by logistic regression. Individuals having a CSF MBP-like material level of > or = 0.1 ng/ml overall showed a greater likelihood of continued improvement at day 40 (p = 0.014) or further improvement between days 5 and 40 (p = 0.003). Those in the first 15 days of worsening and with an elevated CSF MBP-like level were more likely to respond by day 5. Relapsing-remitting and relapsing-progressive forms of the disease were more likely to respond at both time points than were patients with primary or secondary chronic progressive patterns. The Kurtzke disability score at entry and the major anatomical site of the central nervous system symptomatically affected were not predictive of outcome at either time.(ABSTRACT TRUNCATED AT 250 WORDS)

Enkephalins, brain and immunity: modulation of immune responses by methionine-enkephalin injected into the cerebral cavity

There is a large number of interactions at molecular and cellular levels between the nervous system and the immune system. It has been demonstrated that the opioid neuropentapeptide methionine-enkephalin (Met-Enk) is involved in humoral and cell-mediated immune reactions. Met-Enk injected peripherally produces a dual and dose-dependent immunomodulatory effect: high doses suppress, whereas low doses potentiate the immune reactivity. The present mini-review concerns the immunological activity of Met-Enk after its administration into the lateral ventricles of the rat brain, and describes the extraordinary capacity of centrally applied Met-Enk to regulate/modulate the immune function. This survey is composed of sections dealing with (a) the role of opioid peptides in the central nervous system (CNS); (b) the activity of opioid peptides in the immune system; (c) the application of Met-Enk into the cerebral cavity; (d) the influence of centrally administered Met-Enk on nonspecific local inflammatory reaction; (e) the effect of Met-Enk injected intracerebroventricularly (i.c.v.) on specific delayed hypersensitivity skin reaction, experimental allergic encephalomyelitis, anaphylactic shock, plaque-forming cell response, and hemagglutinin production; (f) the central antagonizing action of quaternary naltrexone, an opioid antagonist that does not cross the brain-blood barrier, on Met-Enk-induced immunomodulation; (g) the alteration of immune responsiveness by i.c.v. injection of enkephalinase-degrading enzymes; (h) the participation of the brain-blood/blood-brain barrier in the CNS-immune system interaction; and (i) the role of opioid receptors in immunological activity of Met-Enk. A hypothesis has been advanced for the reaction of Met-Enk and opioid receptor sitting on the cell membrane. This concept suggests that the constellation of chemical residues of enkephalin and receptor in the microenvironment determines the binding between the opioid partners. The plurality of conformational structures of enkephalins and receptors makes possible their involvement in a variety of processes which occur in different physiological systems, including the nervous system and the immune system, and intercommunications between the two systems.

Adrenalectomy aggravates ischemic brain edema in female Sprague-Dawley rats with carotid arteries ligated

The effect of adrenalectomy has been investigated in a model of global cerebral ischemia. After bilateral carotid ligation the mortality rate was increased in adrenalectomized rats, and this effect was prevented by glucocorticoid pre-treatment. Adrenalectomy accelerated the appearance of the symptoms of cerebral ischemia, resulting in a moderate aggravation of brain edema and in a significant decrease in the concentration of high-energy phosphate esters. Our findings support the view that endogenous glucocorticoids may play a role in the amelioration of ischemic brain injuries in rats.

Abnormal adrenal gland metabolism in opioid addicts: implications for clinical treatment

Adrenal gland metabolism is markedly altered in heroin addicts. During daytime hours, the addict may suffer corticoid deficiency of the addisonian type, and in the evening, an excess of the cushingoid type. The high plasma levels of cortisol that are found in the evening in addicts antagonize endogenous opioids in a manner similar to naloxone. In the present study, 72% of the heroin addicts who sought treatment demonstrated reduced adrenal cortisol reserve. Effective immune and stress responses are dependent on adrenal cortisol reserve. This finding provides an explanation for the heroin addict's vulnerability to AIDS and other infectious diseases. One of methadone's greatest attributes is that it helps normalize adrenal metabolism. Clinical methods to at least partially correct adrenal metabolism may enhance current opioid addiction treatment modalities.

The epidemiology of germinal matrix hemorrhage during the first half-day of life

The personal and maternal characteristics of 27 babies with early-onset germinal matrix hemorrhage (EGMH) were compared with those of 280 babies with normal cranial ultrasonograms, studied in a separate clinical trial. None of the mothers of the babies with EGMH had high blood pressure or pre-eclampsia during pregnancy. Gestational age less than 30 weeks and initial pH less than 7.2 indicated increased risks of EGMH, and maternal receipt of steroids indicated reduced risk of EGMH. Thus prenatal and immediately perinatal factors appear to convey much of the information about the risk of EGMH.

Adrenalectomy-induced potentiation of morphine analgesia: reversal by prednisolone

Effects of adrenalectomy (ADX) on analgesic potency and morphine (MOR) content after SC administration of 3.5 or 7 mg/kg of MOR, and effects of prednisolone (PRED) on the ADX-induced effects were studied. ADX significantly potentiated MOR analgesia at both MOR doses, and PRED reversed the ADX-induced potentiation of MOR analgesia, ADX did not affect MOR content in brain and plasma after 3.5 mg/kg MOR, but significantly increased MOR content in brain and plasma after 7 mg/kg MOR, and PRED reversed the ADX-induced increase in the MOR content. Although the analgesic potency of 3.5 mg/kg MOR in ADX group was equipotent with those of 7 mg/kg MOR in sham-operated and PRED-treated ADX groups, MOR content in the former group was significantly lower than those in the latter two groups. These results suggest that ADX potentiates MOR analgesia through both mechanisms of the increased MOR content and the increased sensitivity to MOR, and that the lack of glucocorticoids participates in both of these ADX-induced effects.