Biomedical subjects

F J Tilders

Publications and source records attributed to F J Tilders.

At least 55 records · Page 3Linked to original sources

PubMed1996

Acute stimulation of the hypothalamic-pituitary-adrenal axis by IL-1 beta, TNF alpha and IL-6: a dose response study.

We investigated the effects of i.v. and intracerebroventricular (i.c.v) administration of increasing doses of recombinant human IL-1 beta, TNF alpha and IL-6 on plasma corticosterone (B) levels in rats. Rats were equipped with a jugular cannula for repeated blood sampling anda subgroup of rats also received an i.c.v implanted cannula. I.v. administration of IL-1 beta, TNF alpha or IL-6 and i.c.v administration of IL-1 beta and IL-6 induced a significant dose-dependent increase in plasma B levels, whereas i.c.v injection of TNF alpha in doses up to 1000 ng/rat was not effective. I.v. pretreatment of rats with anti-CRH antiserum had no significant overall effect on the plasma B response to i.v. administered IL-1 beta (500 and 3000 ng/rat), whereas the plasma B response to i.v. TNF alpha or IL-6 administration (3000 ng/rat) were significantly reduced. I.v. pretreatment of the animals with recombinant human IL-1 receptor antagonist (IL-1ra) significantly blocked the plasma B response to i.v. treatment with IL-1 beta, whereas the TNF alpha- and IL-6-induced increases in plasma B levels were not affected. Our data show that 1) i.v. administration of IL-beta, TNF alpha or IL-6 and i.c.v administration of IL-1 beta or IL-6 dose-dependently stimulate the HPA axis; 2) when given i.v. or i.c.v, IL-1 beta is more powerful than TNF alpha and IL-6 in activating the HPA axis; 3) endogenous CRH is involved in the activation of the HPA axis by acute i.v. administration of TNF alpha and IL-6. It is most likely that in case of i.v. treatment with IL-1 beta a CRH-independent mechanism is involved. This study provides no arguments for the involvement of endogenous IL-1 in TNF alpha- or IL-6-induced activation of the HPA axis.

Adrenal Glands↗

PubMed1996

Self-reported stressors, symptom complaints and psychobiological functioning-II: Psychoneuroendocrine variables.

The present study examined resting endocrinological functioning and endocrine responsivity to new challenges as a function of self-reported stress load and symptomatology. Following a baseline period, four groups of male subjects (low-load/low-symptoms; low-load/high-symptoms; high-load/low-symptoms; high-load/high-symptoms) were exposed to stressful films, followed by a rest period. Blood samples were drawn after each film and after the rest condition, and urinary samples were collected during two nights preceding the experimental session. Neuroendocrine variables measured in plasma included adrenaline, noradrenaline, ACTH, cortisol, growth hormone, prolactin, and testosterone. The urinary samples were assayed for noradrenaline and adrenaline (in relation to creatinin). High-symptom subjects had significantly higher plasma levels of noradrenaline and overnight urinary adrenaline levels, whereas their cortisol levels tended to be lower as compared to the low-symptom group. The plasma noradrenaline/cortisol ratio was higher among the high-symptom subjects. However, upon controlling for neuroticism and life style factors (smoking and alcohol consumption), all but the effects on cortisol failed to meet significance criteria. Higher stress load was associated with higher plasma adrenaline responses during the laboratory session, irrespective of neuroticism or life-style measures. These results therefore suggest that in addition to measuring exposure to real-life stressors, it is also necessary to measure outcomes, such as symptoms, and to be aware of the effects of neuroticism and life-style when attempting to understand which specific psychosocial factors effect psychoendocrinological functioning.

Adult↗

PubMed1996

Interleukin-1 receptors on rat brain endothelial cells: a role in neuroimmune interaction?

Inflammation following an infection induces a range of nonspecific symptoms of sickness in animals and humans. The cytokine interleukin-1 (IL-1) mediates many of the brain-mediated symptoms of sickness. Binding sites for IL-1 have been found in mouse brain, but not in the brains of rats. This raises questions as to the involvement of these neuronally localized IL-1 binding sites in the induction of sickness symptoms. Based on observations of IL-1 receptor mRNA in close vicinity to the vasculature in the mouse and rat brain, we studied the possibility that endothelial cells in the rat brain exhibit IL-1 receptors to transduce information to the brain. Ligand binding studies reveal that cultured endothelial cells of adult rat brain exhibit specific binding sites for rat IL-1beta. Polymerase chain reaction experiments demonstrated that mRNA of the type I but not that of the type II IL-1 receptor is present in rat brain endothelial cells. Incubation of these endothelial cells with recombinant rat IL-1beta showed a dose-dependent increase in interleukin-6, prostaglandin E(2), and prostacyclin secretion. Intravenous administration of rat IL-1beta to adult rats enhanced prostaglandin E(2) immunoreactivity in endothelial cells of the brain microvasculature. These results indicate that functional type I IL-1 receptors are present on endothelial cells of adult rat brain. We postulate that circulating IL-1 can be translated by brain endothelial cells into other signals such as interleukin-6 or prostaglandins that have access to the brain and induce sickness symptoms.

Animals↗

PubMed1996

Diurnal variation in resting levels of corticosterone is not mediated by variation in adrenal responsiveness to adrenocorticotropin but involves splanchnic nerve integrity.

To study possible mechanisms controlling diurnal changes in corticosterone (CORT) levels, we tested the CORT responses to ACTH in the morning (AM) and evening (PM) in male Wistar and Sprague-Dawley rats. Rat ACTH-(1-39) or human ACTH-(1-24) (3.75-15 ng/rat) was given as an iv bolus or an intraarterial infusion to (un)anesthetized rats treated with dexamethasone (0.1-0.5 mg/kg, 2-6 h before ACTH). In all conditions studied, no AM/PM differences in CORT responses were found when ACTH was given in vehicle (pH 4.3-7). This contrasts with earlier studies in which ACTH was given in a strongly acid vehicle (pH 1-1.9). Administration of ACTH in such acid vehicle confirmed the reported AM/PM differences in CORT responses (P < 0.05). Because alterations in splanchnic nerve activity can modulate ACTH-induced CORT secretion, we studied the effect of splanchnic nerve transection (SPLNX) on the diurnal change in resting CORT levels in unilaterally adrenalectomized rats. SPLNX reduced resting CORT concentrations in the PM (approximately 50%; P < 0.05), but not in the AM. SPLNX did not abolish the acid vehicle-associated AM/PM differences in CORT responses to ACTH. We conclude that 1) diurnal variation in adrenal responsiveness to ACTH per se does not exist in this rat model; 2) the strongly acid vehicle interacts with ACTH-induced CORT secretion; 3) the PM rise in plasma CORT depends on the integrity of the sympathetic neural input to the adrenal gland.

Adrenal Glands↗

PubMed1996

Short stressor induced long-lasting increases of vasopressin stores in hypothalamic corticotropin-releasing hormone (CRH) neurons in adult rats.

Recently, we demonstrated that single administration of interleukin-1 beta (IL-1) to adult rats induces a long-lasting (weeks) increase of vasopressin (AVP) stores in terminals of CRH neurons in the external zone of the median eminence (ZEME). This is accompanied by hypersecretion of AVP into the pituitary portal circulation and long-lasting hyperresponsiveness of the hypothalamo-pituitary-adrenal (HPA) axis to stressors. Here, we determine whether this form of plasticity of hypothalamic CRH neurons is specific for IL-1 or represents a general response to a stressor. Single exposure of rats to lipopolysaccharide (LPS), IL-1, brain surgery or electric footshocks increases the AVP stores in the ZEME 7 and 11 days later. Exposure to insulin or ether does not affect the AVP stores. The stressors have little or no effect on the CRH stores in the ZEME. The amplitude of the increase in AVP as measured 7-11 days after stimulation correlates with the overall ACTH response to the stressor (area under curve, r = 0.89, P < 0.0001), with the peak ACTH levels (r = 0.52, P < 0.05), but not with the duration of the ACTH response nor with any parameter of the corticosterone response. Administration of ACTH or corticosterone at doses that mimic stress-induced plasma levels does not increase AVP stores 7 days later. We conclude that long-lasting increases of AVP stores in CRH terminals in the ZEME can be induced by various stressors and postulate that the amplitude of such increases depends on the degree of activation of the CRH neurons by the stressor. (NWO grant: 900-543-101.)

Adrenocorticotropic Hormone↗

PubMed1995

Effects of short-term dexamethasone treatment during pregnancy on the development of the immune system and the hypothalamo-pituitary adrenal axis in the rat.

The effects of glucocorticoid (GC) treatment on the mature immune and neuroendocrine system are known to be reversible. However, prenatal GC exposure may have irreversible consequences on the development of the newborn. In this study, possible long-lasting effects of short-term prenatal GC treatment were examined on the developing thymus, spleen and hypothalamo-pituitary adrenal axis (HPA axis). Female rats were given dexamethasone (DEX, 400 micrograms, i.p.) on day 17 and 19 of pregnancy and offspring was studied at several time intervals (1-20 days) after birth, for examination of thymus, spleen, hypothalamus and blood plasma. Examination of thymus and spleen revealed that prenatal exposure to DEX resulted in decreased T cell numbers in thymus and spleen on day 1 after birth. Thymus regeneration after DEX exposure both during pregnancy and in adult life was completed after 24 days. However, the kinetics of regeneration of the thymi after prenatal DEX exposure were different from that seen after DEX in adult life. Whereas DEX treatment during pregnancy resulted in an increased ratio of CD4+/CD8- thymocytes over CD4-/CD8+ thymocytes compared to control groups on day 7 and day 20 after birth (time X treatment interaction; P < 0.05), DEX treatment in adult life did not change this ratio. T cell numbers in the spleen were significantly decreased at all neonatal ages studied. Regarding the hypothalamus, prenatal exposure to DEX altered the pattern of neonatal changes in peptide expression in corticotropin-releasing hormone neurons, with a selective reduction in CRH storage in the median eminence (7 and 9 days after birth) and an increase in AVP storage (9 and 20 days after birth). The ratio of AVP over CRH was significantly increased at all developmental ages studied. No effects were seen on basal ACTH and corticosterone levels in plasma. In conclusion, the kinetics of thymus regeneration after DEX exposure during pregnancy were different from that seen after DEX exposure in adult life. Prenatal DEX exposure also seemed to delay the migration of T cells into the spleen. Furthermore, prenatal DEX treatment exerted major effects on hypothalamic CRH neurons that maintained for at least 20 days after birth, which points towards an enhanced stress responsiveness of the HPA axis in later life.

Adrenocorticotropic Hormone↗

PubMed1995

Intermittent cocaine exposure causes delayed and long-lasting sensitization of cocaine-induced ACTH secretion in rats.

In view of the possible role of the hypothalamus-pituitary-adrenal axis in the long-term effects of drugs of abuse, we studied the response of the hypothalamus-pituitary-adrenal axis to cocaine challenges 3 and 14 days after cocaine withdrawal. Three days after intermittent cocaine exposure, the cocaine-induced increase of plasma adrenocorticotropic hormone (ACTH) is unchanged, whereas after 14 days the ACTH response is enhanced 2-fold. The cocaine-induced increase of plasma corticosterone is enhanced approximately 1.5-fold both 3 and 14 days after cocaine withdrawal. Apparently, prior cocaine treatment causes a delayed sensitization of cocaine-induced ACTH secretion and long-lasting corticosterone hyper-responsiveness. We propose that the long-lasting changes in the hypothalamus-pituitary-adrenal axis may facilitate drug-induced long-term behavioral sensitization.

Adrenocorticotropic Hormone↗

PubMed1995

Appearance of inducible nitric oxide synthase in the rat central nervous system after rabies virus infection and during experimental allergic encephalomyelitis but not after peripheral administration of endotoxin.

The cellular localization of inducible (iNOS) and constitutive (cNOS) nitric oxide synthase was studied in rats by immunocytochemical techniques involving specific iNOS and cNOS directed antibodies and by NADPH-diaphorase histochemistry. Paraformaldehyde-fixed vibratome sections of brains and cryostat sections of peripheral lymph nodes were studied of rats treated with endotoxin (2.5 micrograms/kg or 2.5 mg/kg i.v.), rats infected with rabies virus, and rats exposed to experimental allergic encephalomyelitis (EAE). Endotoxin-treated animals showed no appearance of immunoreactive iNOS (ir-iNOS) cells in the brain with the exception of a few microglial cells near the median eminence and some meningeal macrophages. In the same animals however, iNOS-immunoreactive cells were found in peripheral lymph nodes. Neurons that stain positive for cNOS and for NADPH-diaphorase could be observed in brains of control as well as of endotoxin-treated animals with a similar distribution and staining intensity. In contrast, animals that had been infected with rabies virus or subjected to EAE, showed the appearance of ir-iNOS-positive cells in several brain areas. These cells are located near blood vessels and lesion sites. The majority of these cells are GSA-I-B4 isolectin-positive and therefore are likely to represent macrophages. Our data suggest that increased production of nitric oxide may play a role in the altered brain functions in rabies-infected and EAE rats. On the contrary, increased nitric oxide production is probably not involved in the non-specific symptoms of sickness induced by endotoxin.

Animals↗

PubMed1995

Endotoxin-induced appearance of immunoreactive interleukin-1 beta in ramified microglia in rat brain: a light and electron microscopic study.

Interleukin-1 plays an important role as mediator of endotoxin-induced responses in the brain such as fever, sleep, anorexia, behavioural and neuroendocrine changes. In the present study, interleukin-1 beta immunocytochemistry has been performed at the light and electron microscopic level to study the cellular and subcellular localization of interleukin-1 beta in the brains of rats given endotoxin or saline. Light microscopic analysis of rats killed 4, 8 or 24h after endotoxin (2.5 mg/kg) given intraperitoneally or intravenously revealed a region-specific localization of immunoreactive interleukin-1 beta in macrophages and microglial cells. After saline treatment, no induction of interleukin-1 beta immunoreactivity occurred in the brain. After administration of endotoxin, many interleukin-1 beta-positive cells were found in the meninges, choroid plexus, circumventricular organs, cerebral cortex and hypothalamus. The number of interleukin-1 beta-positive microglial cells reached a maximum 8 h after administration of endotoxin, irrespective of the route of administration. In general, more interleukin-1 beta-positive microglial cells were found after intravenous than after intraperitoneal administration of endotoxin. Interleukin-1 beta-positive microglial cells were often grouped in patches in the vicinity of blood vessels. At the surface of the cerebral cortex, in the meninges, intermediate cell forms between interleukin-1 beta-positive macrophages and microglial cells were found. interleukin-1 beta-positive perivascular microglia were localized at the brain side of the basal lamina. Immunoreactive interleukin-1 beta was found at the luminal side of the endothelial cells lining the venules. Furthermore, microglial cells that extended their processes into the ependymal layer of the third ventricle were observed. Results of the electron microscopic studies revealed immunoreactive interleukin-1 beta in many cells with the cellular characteristics of microglial cells, but also, in some cells, identified as astrocytes. In microglial cells, immunoreactive interleukin-1 beta was found in the cytoplasm but not in the endoplasmatic reticulum or Golgi apparatus. These results show that after peripheral administration of endotoxin, immunoreactive interleukin-1 beta is induced in macrophages in the meninges and in the choroid plexus, as well as in microglial cells in parenchyma. Interleukin-1 beta produced by these cells may serve as a signal for adjacent or more distant targets (neurons, endothelial cells, microglial cells) to play a role in the induction of non-specific symptoms of sickness.

Animals↗

PubMed1995

Effects of monoclonal antibodies to specific epitopes of rat interleukin-1 beta (IL-1 beta) on IL-1 beta-induced ACTH, corticosterone and IL-6 responses in rats.

Recently, we developed a panel of monoclonal antibodies (MoAbs) to rat IL-1 beta and found that MoAbs binding to the aminoacid sequences 66-85 and 123-143 of mature rIL-1 beta inhibited the binding of rIL-1 beta to murine EL4 cells. Here we study whether MoAbs to these and other domains of IL-1 interfere with the biological effects of rIL-1 beta in adult male rats in vivo. Administration of rIL-1 beta (1 or 5 micrograms/kg i.v.) enhanced the plasma concentrations of ACTH, corticosterone (CORT) and of IL-6 in a time- (0.5-4 h) and dose-dependent manner. Because 2 h after 5 micrograms/kg i.v., all three parameters were consistently elevated, this dose and time interval was used for further studies. Prior to injection, rIL-1 beta was incubated alone or in the presence of a MoAb (10 mg/kg) for 30 min at 37 degrees C or at 4 degrees C. Plasma ACTH, CORT and IL-6 responses to these mixtures are compared to those obtained after preincubation of rIL-1 beta with a non-IL-1 binding MoAb (PEN7). SILK 3, a MoAb that binds to the 66-85 domain of rIL-1 beta, reduced the ACTH and IL-6 responses by 48 and 45% respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗

PubMed1995

Circulating tumor necrosis factor-alpha does not mediate endotoxin-induced hypothermia in rats.

The present study was designed to investigate the role of macrophages and circulating tumor necrosis factor-alpha (TNF-alpha) in the endotoxin-induced hypothermic responses in rats. Intravenous as well as intraperitoneal administration of endotoxin to male Wistar rats (0.5 mg/kg) led to increased plasma TNF-alpha concentrations and a transient hypothermia, which reached its nadir after 90 min. The hypothermia and plasma TNF-alpha responses to endotoxin were abolished after elimination of peripheral macrophages. Seven days after the first challenge, tolerance of the hypothermic response was found if the same dose was administered intraperitoneally but not if it was administered intravenously. Tolerance of the TNF-alpha response was induced irrespective of the route of endotoxin administration. We hypothesize that, after intravenous administration of endotoxin, macrophage-dependent and -independent mechanisms are activated, whereas the hypothermic response to intraperitoneal endotoxin involves primarily macrophage-dependent mechanisms. These mechanisms may relate to the prime targets reached by endotoxin, such as macrophages and endothelial cells. Because the development of tolerance of the hypothermic response is dependent on the route of endotoxin administration, whereas that of the plasma TNF-alpha response is not, we conclude that circulating TNF-alpha is not the macrophage-derived cryogenic signal that triggers the hypothermic response.

Animals↗

PubMed1995

Corticotropin-releasing hormone mRNA levels in the paraventricular nucleus of patients with Alzheimer's disease and depression.

OBJECTIVE: Greater activity of the hypothalamic-pituitary-adrenal (HPA) axis is associated with specific neurological and psychiatric disorders, including Alzheimer's disease and depression. Hyperactivation of paraventricular corticotropin-releasing hormone (CRH) neurons may form the basis of this increased activity of the HPA axis. METHOD: Activation of the CRH neurons was determined through measurement of the amount of CRH-mRNA in the paraventricular nucleus by using quantitative, in situ hybridization histochemistry with systematically sampled frontal sections through the hypothalamus of routinely formalin-fixed and paraffin-embedded autopsy brain material of 10 comparison subjects, 10 patients with Alzheimer's disease, and seven depressed patients. RESULTS: CRH-mRNA levels in the paraventricular nucleus of Alzheimer's patients were markedly higher than those of comparison subjects, whereas CRH-mRNA levels in the paraventricular nucleus of depressed patients were even higher than the levels of Alzheimer's patients. CONCLUSIONS: Paraventricular CRH neurons in Alzheimer's disease and depression are hyperactivated, and this hyperactivation may contribute to the etiology of these disorders.

Adult↗

PubMed1995

Domains of rat interleukin 1 beta involved in type I receptor binding.

In the present study the inhibitory effects of a panel of 21 monoclonal antibodies (moabs) to rat interleukin 1 beta (rIL-1 beta) on the binding of 125I-labeled rIL-1 beta to murine type I IL-1 receptors on EL4 cells were investigated. Furthermore, the epitopes of these moabs were determined by the use of the pepscan technique, and these epitopes were visualized on a three-dimensional model of rIL-1 beta. Some moabs (SILK 3, 4, 5, 6, and 22) inhibited receptor binding of radioiodinated rIL-1 beta at concentrations that are similar to the dissociation constant values of antibody-rIL-1 beta binding. Another group of moabs (SILK 7, 11, 20, 21, and 23) also inhibited receptor binding but only at concentrations that are 10-150 times higher than their dissociation constants. A large group of moabs did not affect receptor binding in the concentration range tested, and two moabs enhanced the binding of rIL-1 beta to type I receptors. The result of pepscan analysis shows that the moabs bound to one or more of the amino acid sequences 35-49, 66-85, 78-97, 106-124, and 123-143 of mature rIL-1 beta. Modeling of rIL-1 beta shows that the binding domains of SILK 4, 5, 6, and 22 (sequence 123-143) is located at the closed end of the molecule, indicating that this part of rIL-1 beta harbors domains that are crucial for type I receptor binding. The binding domain of SILK 3 (sequence 66-85) is also located at this end of the molecule. In contrast, the binding domains of SILK 7, 11, 20, 21, and 23 (sequence 78-97) are located at the open end of the molecule, which is at the same face as the amino- and carboxy-terminals. The binding domain of SILK 16 (sequence 106-124) is positioned at the center of the molecule. It is concluded that the closed end of rIL-1 beta contains sequences that are crucial for its binding to type I receptors on murine EL4 cells. Because of the high concentrations of antibodies to residues 78-97 of rIL-1 beta that are needed to interfere with receptor binding, the importance of these domains in binding to type I receptors remains uncertain.

Animals↗

PubMed1995

Subdiaphragmatic vagotomy suppresses endotoxin-induced activation of hypothalamic corticotropin-releasing hormone neurons and ACTH secretion.

In order to assess the possibility that endotoxin-induced activation of the hypothalamus-pituitary-adrenal (HPA) axis is mediated by vagal afferents, we studied the effects of transection of the vagal nerves on endotoxin-induced Fos expression in hypothalamic corticotropin-releasing hormone (CRH) neurons and plasma ACTH and corticosterone responses. Groups of rats were subjected to sham surgery, complete subdiaphragmatic vagotomy (SVGX), or selective transection of the hepatic branch (HVGX). Two weeks after surgery, endotoxin or saline was injected i.p. and rats were sacrificed by decapitation two hours later. SVGX blocked or attenuated the ACTH response to 20 and 250 micrograms/kg endotoxin, respectively. HVGX did not suppress the ACTH response to either endotoxin dose. In addition, corticosterone responses were not affected by SVGX or HVGX. The endotoxin-induced Fos expression in CRH neurons was suppressed in SVGX, but not in HVGX animals. These observations lead us to postulate that the CRH and ACTH responses to a low dose of endotoxin are mediated by vagal afferents. The responses to a high dose of endotoxin involve additional neuronal or humoral pathways.

Adrenocorticotropic Hormone↗

PubMed1995

Interleukin-1-induced long-lasting changes in hypothalamic corticotropin-releasing hormone (CRH)--neurons and hyperresponsiveness of the hypothalamus-pituitary-adrenal axis.

Hypothalamic CRH neurons that control ACTH secretion from the pituitary gland have secretory terminals in the external zone of the median eminence (ZEME). These neurons can coproduce vasopressin (AVP), a neuropeptide that potentiates the ACTH releasing effects of CRH. Recently, we found increased AVP production in adult rats weeks after single exposure to a stressor, which may play a role in event-induced stress disorders. Here, we describe the long-term changes in the HPA axis of adult male rats following a single exposure to a stressor, the cytokine interleukin-1 beta (IL-1 beta). The effects on storage and release of AVP and CRH were established by quantitative immunocytochemistry, the effects on ACTH and corticosterone responses by radioimmunoassay. Single administration of IL-1 beta (5 micrograms/kg i.p.) induces a delayed (at least 4 d) and a long-lasting (at least 3 weeks) increase of vasopressin (AVP) stores in CRH terminals of the ZEME without affecting the CRH stores, and a marked increase of the fraction of CRH terminals that costore AVP. Eleven days after IL-1 beta administration, a second IL-1 beta challenge causes a marked depletion of the AVP stores in the ZEME within 2 hr, which is not seen in rats treated with vehicle 11 d earlier. This is accompanied by twofold higher ACTH and corticosterone responses, as compared to those in vehicle pretreated rats. IL-1 beta-pretreated rats also showed increased ACTH and corticosterone responses to electric footshocks. We conclude that transient activation of the HPA axis by a single administration of IL-1 beta induces a delayed and long-lasting hyperproduction, hyperstorage, and hypersecretion of AVP from hypothalamic CRH neurons that results in hyperresponsiveness of the HPA axis to subsequent stimuli.

Animals↗

PubMed1994

Involvement of hypothalamic corticotropin-releasing factor neurons in behavioral responses to novelty in rats.

The purpose of this experiment was to investigate whether endogenous corticotropin-releasing factor (CRF) within the paraventricular nucleus of the hypothalamus (PVN) is involved in the alteration of locomotor activity related to a novel, presumably stressful, environment in rats. Impairment of the function of CRF-containing neurons was effected by immunotargeting ricin A chain toxin to these cells with a monoclonal antibody to CRF (CRF-MAb/toxins). CRF-MAb/toxins administered into the PVN 2 weeks prior to testing produced an increase in locomotor activity during exposure to novel environment photocell cages. This behavioral activation was maintained throughout the 120 min experimental session, but was not present when the rats where introduced to the same photocell cages after extensive habituation. These results suggest that the effect induced by CRF-MAb/toxin treatment was related to the exploration of the novel environment, and was not due to a generalized locomotor hyperactivity. This effect was accompanied by a 53% and 61% CRF decrease in the hypothalamus and the median eminence, respectively. Injection of CRF-MAb/toxins into the ventromedial nucleus of the hypothalamus did not modify the locomotor activity in either unfamiliar or familiar conditions. These data suggest that CRF neurons within the PVN may participate not only in the activation of the pituitary adrenal axis associated with stressors but also as physiological mediators of the behavioral responses to stress.

Amygdala↗

PubMed1994

Age-related increase in the total number of corticotropin-releasing hormone neurons in the human paraventricular nucleus in controls and Alzheimer's disease: comparison of the disector with an unfolding method.

It has been hypothesized that the corticotropin-releasing hormone (CRH) neurons of the hypothalamic paraventricular nucleus (PVN) become hyperactive with age, and even more so in Alzheimer's disease. This hyperactivity could be due to an increased production of CRH per neuron, or an increased number of PVN neurons producing CRH, or both. As a first step in elucidating which of these biological mechanisms might be operative, we have estimated the absolute number of CRH immunoreactive neurons in the PVN of 10 human control subjects between 36 and 91 years of age and 10 Alzheimer patients between 40 and 97 years of age. CRH neurons were immunocytochemically detected in 6 microns paraffin sections with the aid of a highly specific monoclonal antibody to CRH. The antibody signal was amplified by the biotin-streptavidin and alkaline phosphatase methods. The absolute number of CRH neurons in the PVN was obtained by multiplying the number of CRH neurons in a unit volume (NV) by the total volume of the PVN. Two different methods were used to estimate the NV: an unfolding method and a disector method (about three times more time-consuming). Compared to the disector, the unfolding method consistently yielded a lower cell number for all patients by 38% (+/- 2.8%; mean +/- SEM). However, both methods yielded an increase in the absolute number of CRH neurons in control and Alzheimer patients with age. No statistically significant difference in the absolute number of CRH neurons was found between control and Alzheimer patients with both methods. The age-dependent increase in the absolute number of CRH neurons within the PVN of both control and Alzheimer patients is interpreted as a sign of activation of the CRH neurons with age.

Aged↗

PubMed1994

Pituitary-adrenal and interleukin-6 responses to recombinant interleukin-1 in neonatal rats.

The cytokine interleukin-1 (IL-1) is a potent activator of the hypothalamic-pituitary-adrenal (HPA) axis. During postnatal development, the rat appears to be hyporesponsive to many stimuli which activate the HPA system in adulthood. Since hyporesponsiveness depends to a large extent on the stimulus, these experiments investigated the ontogeny of the HPA axis and interleukin-6 (IL-6) responses to IL-1 beta. Six-, 9-, and 18-day-old pups were injected with human recombinant IL-1 beta and plasma ACTH, corticosterone (CORT) and IL-6 levels were measured. IL-1 beta administration resulted in age-dependent endocrine and immune responses. The younger neonates secreted less ACTH and CORT and more IL-6. This was not due to a lowered capacity of the pituitary to synthesize and secrete ACTH since peptide levels following adrenalectomy did not reveal age differences. These data suggest that the diminished response to IL-1 beta is due to the immaturity of neural circuits which may be required to fully activate the HPA axis to immune signals.

Adrenalectomy↗