Alpha-helical Corticotropin-releasing Factor Research Articles

Social interaction reward in rats has anti-stress effects.

Social interaction in an alternative context can be beneficial against drugs of abuse. Stress is known to be a risk factor that can exacerbate the effects of addictive drugs. In this study, we investigated whether the positive effects of social interaction are mediated through a decrease in stress levels. For that purpose, rats were trained to express cocaine or social interaction conditioned place preference (CPP). Behavioural, hormonal, and molecular stress markers were evaluated. We found that social CPP decreased the percentage of incorrect transitions of grooming and corticosterone to the level of naïve untreated rats. In addition, corticotropin‐releasing factor (CRF) was increased in the bed nucleus of stria terminalis after cocaine CPP. In order to study the modulation of social CPP by the CRF system, rats received intracerebroventricular CRF or alpha‐helical CRF, a nonselective antagonist of CRF receptors. The subsequent effects on CPP to cocaine or social interaction were observed. CRF injections increased cocaine CPP, whereas alpha‐helical CRF injections decreased cocaine CPP. However, alpha‐helical CRF injections potentiated social CPP. When social interaction was made available in an alternative context, CRF‐induced increase of cocaine preference was reversed completely to the level of rats receiving cocaine paired with alpha‐helical CRF. This reversal of cocaine preference was also paralleled by a reversal in CRF‐induced increase of p38 MAPK expression in the nucleus accumbens shell. These findings suggest that social interaction could contribute as a valuable component in treatment of substance use disorders by reducing stress levels.

Perturbations in Effort-Related Decision-Making Driven by Acute Stress and Corticotropin-Releasing Factor.

Acute stress activates numerous systems in a coordinated effort to promote homeostasis, and can exert differential effects on mnemonic and cognitive functions depending on a myriad of factors. Stress can alter different forms of cost/benefit decision-making, yet the mechanisms that drive these effects, remain unclear. In the present study, we probed how corticotropin-releasing factor (CRF) may contribute to stress-induced alterations in cost/benefit decision-making, using an task where well-trained rats chose between a low effort/low reward lever (LR; two pellets) and a high effort/high reward lever (HR; four pellets), with the effort requirement increasing over a session (2, 5, 10, and 20 presses). One-hour restraint stress markedly reduced preference for the HR option, but this effect was attenuated by infusions of the CRF antagonist, alpha-helical CRF. Conversely, central CRF infusion mimicked the effect of stress on decision-making, as well as increased decision latencies and reduced response vigor. CRF infusions did not alter preference for larger vs smaller rewards, but did reduce responding for food delivered on a progressive ratio, suggesting that these treatments may amplify perceived effort costs that may be required to obtain rewards. CRF infusions into the ventral tegmental area recapitulated the effect of central CRF treatment and restraint on choice behavior, suggesting that these effects may be mediated by perturbations in dopamine transmission. These findings highlight the involvement of CRF in regulating effort-related decisions and suggest that increased CRF activity may contribute to motivational impairments and abnormal decision-making associated with stress-related psychiatric disorders such as depression.

Corticotropin-releasing factor is a downstream mediator of the beta-melanocyte-stimulating hormone-induced anorexigenic pathway in chicks

Proopiomelanocortin (POMC, a precursor of anorexigenic neuropeptides) neurons in hypothalamus suppresses food intake in both mammals and chickens. In mammals, several lines of evidence suggest that POMC-derived anorexigenic peptides upregulate mRNA levels of anorexigenic peptides such as corticotropin-releasing factor (CRF) and thyrotropin-releasing factor and downregulate mRNA levels of orexigenic peptides such as orexin and melanin-concentrating hormone. However, the POMC-induced anorexigenic pathway in chickens has not been well characterized. In the present study, we investigated how POMC neurons regulate mechanisms of food intake using an anorexigenic peptide, beta-melanocyte-stimulating hormone (β-MSH), derived from the post-transcriptional cleavage of POMC. Central administration of β-MSH in chicks significantly suppressed food intake, and importantly, this suppression was accompanied by a significant upregulation of CRF mRNA levels. Furthermore, the CRF type 2 receptor antagonist alpha-helical CRF significantly reversed the anorexigenic action of β-MSH. These findings indicate that CRF and its receptor, CRF type 2 receptor, act as the major mediators in β-MSH-induced anorexigenic action in chicks. β-MSH significantly increased orexin mRNA levels and did not alter mRNA levels of thyrotropin-releasing factor and melanin-concentrating hormone in chicks, suggesting that the β-MSH-induced anorexigenic pathway in chicks is different from that in mammals. Increases in orexin mRNA levels were accompanied by significant decreases in plasma glucose concentration, suggesting that orexin mRNA might be stimulated by β-MSH-induced hypoglycemia. Thus, this study demonstrates the direct evidence that CRF is a critical downstream target in the β-MSH-induced anorexigenic pathway in chicks.

Central hyperventilatory action of the stress-related neurohormonal peptides, corticotropin-releasing factor and urotensin-I in the trout Oncorhynchus mykiss

The stress-related neurohormonal peptides corticotropin-releasing factor (CRF) and urotensin-I (U-I), an ortholog of mammalian urocortin 1, are widely distributed in the central nervous systems of teleost fish but little is known about their possible central neurotropic actions. In the present study, we investigated the effect of intracerebroventricular (ICV) injection of CRF and U-I (1–10 pmol) on ventilatory and cardiovascular variables in our established unanaesthetized trout model. CRF and U-I produced a significant dose-dependent and long-lasting increase in the ventilatory frequency (VF) and the ventilatory amplitude (VA). Consequently the net effect of these peptides was a hyperventilatory response since the total ventilation (VTOT) was significantly elevated. However, CRF evoked a significant hyperventilatory response 5–10 min sooner than that observed after ICV administration of U-I and the hyperventilatory effect of 10 pmol CRF was twofold higher than that of equimolar dose of U-I. Pre-treatment of the trout with the antagonist, alpha-helical CRF 9–41, significantly reduced by about threefold the CRF-induced increase in VF, VA and VTOT. The most significant cardiovascular action of central CRF and U-I was to evoke a hypertensive response without changing the heart rate. Peripheral injection of CRF and U-I at doses of 5 and 50 pmol produced no change in VF, VA or VTOT. Only a transient hypertensive response without change in heart rate was observed after the injection of the highest dose of U-I. Our results demonstrate that in a teleost fish, CRF and U-I produce a potent hyperventilatory response only when injected centrally. The two endogenous stress-related neuropeptides may play an important stimulatory role acting as neurotransmitters and/or neuromodulators in the central control of ventilatory apparatus during stress.

Identification of brain target neurons using a fluorescent conjugate of corticotropin-releasing factor

Corticotropin-releasing factor (CRF) is a peptide well known for its role in coordinating various neuroendocrine, autonomic, and behavioral components of the vertebrate stress response, including rapid enhancement of locomotor activity. Although CRF's locomotor enhancing properties are well documented, the neuronal mechanisms and specific target neurons that underlie the peptide's effect on locomotor behavior remain poorly understood. In the present study, we describe the synthesis and functional characteristics of a CRF rhodamine analogue TAMRA-X conjugate mixture (CRF-TAMRA 1), to be used for tracking this peptide's internalization into target neurons in the brainstem of an amphibian, the roughskin newt ( Taricha granulosa). CRF-TAMRA 1 conjugate administration into the lateral cerebral ventricle resulted in a rapid, endosomal-like internalization of fluorescence into brainstem medullary neurons. In addition, central CRF-TAMRA 1 administration produced neurobehavioral effects comparable to the native peptide, effects that were blocked by pre-treatment with the CRF receptor antagonist, alpha-helical CRF. Taken together, our results show the efficacy of CRF-TAMRA 1 as a novel tool for tracking CRF internalization into targets neurons in vivo and ultimately, aiding in elucidating the neuronal mechanisms and circuitry underlying CRF's influence on behavioral and physiological responses to stress.

Hypothalamic Corticotrophin‐Releasing Factor and Norepinephrine Mediate Sympathetic and Cardiovascular Responses to Acute Intracarotid Injection of Tumour Necrosis Factor‐α in the Rat

Systemic administration of tumour necrosis factor (TNF)-alpha induces the release of norepinephrine in the paraventricular nucleus (PVN) of hypothalamus and an increase in expression of corticotrophin-releasing factor (CRF) and CRF type 1 receptors. We explored the hypothesis that CRF and norepinephrine in PVN mediate the cardiovascular and sympathetic responses to acute systemic administration of TNF-alpha. In anaesthetised rats, the increases in arterial pressure and heart rate induced by intracarotid artery injection of TNF-alpha were attenuated by intracerebroventricular (ICV) injection of either the alpha 1-adrenergic antagonist prazosin or the CRF antagonist alpha-helical CRF. Prazosin blocked the TNF-alpha-induced increase in renal sympathetic nerve activity (RSNA), whereas alpha-helical CRF substantially reduced the RSNA response. Conversely, CRF and the alpha 1-adrenergic agonist phenylephrine, administered ICV, both elicited increases in PVN neuronal activity, RSNA, arterial pressure and heart rate. Microinjection of CRF and phenylephrine directly into PVN evoked smaller responses. These results are consistent with the hypothesis that norepinephrine and CRF in the PVN mediate the cardiovascular and sympathetic responses to acute systemic administration of TNF-alpha.

Corticotropin-releasing factor in the basolateral amygdala enhances memory consolidation via an interaction with the beta-adrenoceptor-cAMP pathway: dependence on glucocorticoid receptor activation.

Extensive evidence indicates that stress hormone effects on the consolidation of emotionally influenced memory involve noradrenergic activation of the basolateral complex of the amygdala (BLA). The present experiments examined whether corticotropin-releasing factor (CRF) modulates memory consolidation via an interaction with the beta-adrenoceptor-cAMP system in the BLA. In a first experiment, male Sprague Dawley rats received bilateral infusions of the CRF-binding protein ligand inhibitor CRF(6-33) into the BLA either alone or together with the CRF receptor antagonist alpha-helical CRF(9-41) immediately after inhibitory avoidance training. CRF(6-33) induced dose-dependent enhancement of 48 h retention latencies, which was blocked by coadministration of alpha-helical CRF(9-41), suggesting that CRF(6-33) enhances memory consolidation by displacing CRF from its binding protein, thereby increasing "free" endogenous CRF concentrations. In a second experiment, intra-BLA infusions of atenolol (beta-adrenoceptor antagonist) and Rp-cAMPS (cAMP inhibitor), but not prazosin (alpha(1)-adrenoceptor antagonist), blocked CRF(6-33)-induced retention enhancement. In a third experiment, the CRF receptor antagonist alpha-helical CRF(9-41) administered into the BLA immediately after training attenuated the dose-response effects of concurrent intra-BLA infusions of clenbuterol (beta-adrenoceptor agonist). In contrast, alpha-helical CRF(9-41) did not alter retention enhancement induced by posttraining intra-BLA infusions of either cirazoline (alpha(1)-adrenoceptor agonist) or 8-br-cAMP (cAMP analog). These findings suggest that CRF facilitates the memory-modulatory effects of noradrenergic stimulation in the BLA via an interaction with the beta-adrenoceptor-cAMP cascade, at a locus between the membrane-bound beta-adrenoceptor and the intracellular cAMP formation site. Moreover, consistent with evidence that glucocorticoids enhance memory consolidation via a similar interaction with the beta-adrenoceptor-cAMP cascade, a last experiment found that the CRF and glucocorticoid systems within the BLA interact in influencing beta-adrenoceptor-cAMP effects on memory consolidation.

Intracerebroventricular administration of corticotropin-releasing factor antagonist attenuates arousal response accompanied by yawning behavior in rats

We have reported that an arousal response accompanied by yawning behavior can be evoked by electrical and chemical stimulation of the hypothalamic paraventricular nucleus (PVN) in rats, although the mechanism responsible for the arousal response accompanied by yawning evoked by PVN stimulation is still unknown. In the present study, we examined the involvement of corticotropin-releasing factor (CRF) in the arousal response during yawning induced by electrical stimulation of the PVN in anesthetized, spontaneous breathing rats using intracerebroventricular (icv) injection of alpha-helical CRF, a CRF antagonist (4.2 microg, lateral ventricle). The electrocorticogram (ECoG) was recorded to evaluate arousal responses during yawning. Fast Fourier transform was used to obtain the power spectrum in delta (0.5-4 Hz), theta (4-8 Hz), alpha (8-13 Hz), and beta (13-20 Hz) bands. We also recorded the intercostal electromyogram as an index of inspiratory activity and blood pressure (BP) as an index of autonomic function to evaluate yawning response. PVN stimulation induced significant increases in relative powers of theta, alpha, and beta bands, but not delta band, concurrent with yawning events regardless of icv injection, though the relative powers after icv injection of alpha-helical CRF were significantly lower than those after saline injection. These findings suggest that CRF neurons in the PVN are primarily responsible for the arousal response accompanied by yawning behavior.

Differential corticosterone responses to stress in the lung in two strains of Flinders rats

Acute stress affects a variety of organs and cellular systems. These include the hypothalamic-pituitary-adrenal (HPA) axis, corticotropin-releasing factor (CRF), mast cells and nerves. Flinders-sensitive (FSL) rat strains have hypercholinergic responses and are more sensitive than Flinders-resistant rats (FRL) to anaphylaxis. To investigate the effects of acute water avoidance stress (1 h) on FSL and FRL tracheal epithelial tissue. We measured short circuit current (I(sc)) as a measure of tracheal response, and the effect of substance P (SP) on tracheal epithelium in Ussing chambers. Electron microscopy was performed to assess mast cell activation. Both strains showed increased I(sc) responses to stress, inhibited by prior injection of the CRF receptor 1 and 2 antagonist, alpha-helical CRF-(9-41). No increases in conductance were seen. Stress responses were accompanied by electron microscopic morphologic evidence for mast cell degranulation, which was not completely inhibited by alpha-helical CRF-(9-41) pre-treatment. Stress primed the epithelium for an enhanced response to SP in FSL, but this again was not inhibited by alpha-helical CRF-(9-41). FRL had 2.5 times the corticosterone response of FSL. Acute stress affects the tracheal epithelium, not accompanied by changes in ion permeability, but associated with mast cell degranulation. Because blunted HPA axis responses are associated with vulnerability to inflammation, this may partially explain the findings. These stress effects on the lung have a genetic basis associated with relative corticosterone responses, are complex and only in part mediated by CRF.

The role of corticotropin-releasing factor in behavioural responses to stress.

Corticotropin-releasing factor (CRF), when administered directly into the CNS, can have activating properties on behaviour and can enhance behavioural responses to stress. CRF injected intraventricularly produces a dose-dependent increase in locomotor activity and increased responsiveness to an acoustic startle stimulus. However, this profile of activation changes to enhanced suppression of behaviour in stressful situations and includes increased freezing, increased conditioned suppression, increased conflict, decreased feeding and decreased behaviour in a novel open field. These effects of CRF are independent of the pituitary-adrenal axis and can be reversed by the CRF antagonist alpha-helical CRF(9-41). More importantly, the CRF antagonist can also reverse many behavioural responses to stressors. alpha-Helical CRF(9-41) reverses stress-induced fighting behaviour, stress-induced freezing, stress-induced suppression of feeding, stress-induced decreases in exploration of an elevated plus maze, fear-potentiated startle and the development of conditioned suppression. Intracerebral microinjections suggest that the amygdala may be an important site for the anti-stress effects of alpha-helical CRF(9-41). These results suggest that endogenous CRF systems in the CNS may have a role in mediating behavioural responses to stress and further suggest that CRF in the brain may function as a fundamental behavioural activating system. This CRF system may be particularly important in situations where an organism must mobilize not only the pituitary-adrenal system but also the CNS in response to environmental challenge.

Effect of ramosetron on conditioned emotional stress-induced colonic dysfunction as a model of irritable bowel syndrome in rats

The aim of this study was to establish a pathophysiologic model of irritable bowel syndrome, and then to evaluate the pharmaceutical efficacy of ramosetron, a potent serotonin 3 (5-HT(3)) receptor antagonist, and other anti-irritable bowel syndrome agents in this model. Rats stressed by a conditioned stress procedure exhibited marked prolongation of freezing time, an index of fear level, and an increase in the frequency of defecation (P<0.01). A corticotropin-releasing factor (CRF) antagonist, alpha-helical CRF, inhibited both defecation and freezing behavior, while the antidiarrheal loperamide inhibited defecation only. The 5-HT(3) receptor antagonists ramosetron, cilansetron and alosetron also inhibited defecation (ED(50) values: 0.012, 0.094, 0.078 mg/kg p.o., respectively) without affecting freezing behavior. Ramosetron showed longer-lasting effect on defecation than cilansetron. Stress also resulted in increases in both proximal and distal colonic transit rates. Ramosetron and other 5-HT(3) receptor antagonists at doses inhibiting stress-induced defecation also ameliorated both stress-stimulated colonic transit rates. These results suggest that ramosetron, as well as agents used for the treatment of irritable bowel syndrome with diarrhea, has beneficial effects against emotional stress-induced colonic dysfunction. Furthermore, this emotional stress model may be useful in evaluation of drugs to treat irritable bowel syndrome presenting with diarrhea.

Stress-induced relapse to cocaine seeking: roles for the CRF2 receptor and CRF-binding protein in the ventral tegmental area of the rat

Footshock reinstates cocaine seeking in cocaine-experienced rats by inducing corticotropin-releasing factor (CRF) and glutamate release in the ventral tegmental area (VTA) and thus activating VTA dopaminergic neurons. Footshock-induced VTA glutamate release, dopamine activation and reinstatements are blocked by VTA administration of a alpha-helical CRF, a nonselective CRF receptor antagonist. The effects of selective CRF antagonists have not yet been reported. The present studies were designed to explore the roles of VTA CRF receptor subtypes and CRF-BP in these effects induced by footshock. Rats were first trained to lever-press for intravenous cocaine (1 mg/infusion/0.13 ml, FR-1 schedule), and then tested under extinction conditions until response rates returned to the pretraining baseline. Reinstatements, VTA glutamate and dopamine levels [microdialysis with high performance liquid chromatography (HPLC)] were then assessed, under various pharmacological conditions, after mild inescapable footshock. Footshock-induced reinstatement of cocaine seeking and release of VTA glutamate and dopamine were blocked by selective blockade of VTA CRF(2) receptors (CRF(2)Rs) but not CRF(1)Rs. VTA perfusion of CRF or CRF(2)R agonists that have strong affinity for CRF-BP mimicked the effects induced by footshock while CRFR agonists that do not bind CRF-BP were ineffective. CRF(6-33), which competes for the CRF binding site on CRF-BP, attenuated the effects of CRF or urocortin I on VTA glutamate and dopamine release and on reinstatement of cocaine seeking. The present studies revealed a role of VTA CRF-BP and suggest an involvement of CRF(2)R in the effectiveness of stress in triggering glutamate and dopamine release and cocaine seeking in drug-experienced animals.

Pathways involved in gut mucosal barrier dysfunction induced in adult rats by maternal deprivation: corticotrophin‐releasing factor and nerve growth factor interplay

Neonatal maternal deprivation (NMD) increases gut paracellular permeability (GPP) through mast cells and nerve growth factor (NGF), and modifies corticotrophin-releasing factor (CRF) and corticosterone levels. CRF, corticosterone and mast cells are involved in stress-induced mucosal barrier impairment. Consequently, this study aimed to specify whether corticosteronaemia and colonic expression of both preproCRF and CRF are modified by NMD, and to determine if altered expression may participate in the elevated GPP in connection with NGF and mast cells. Male Wistar rat pups were either separated from postnatal days 2-14, or left undisturbed with their dam. At 12 weeks of age, adult rats were treated with mifepristone (an antagonist of corticoid receptors), alpha-helical CRF((9-41)) (a non-specific CRF receptor antagonist), or SSR-125543 (CRF-R(1) receptor antagonist). We also determined corticosteronaemia and both colonic preproCRF and CRF expression. Then, control rats were treated by CRF, doxantrazole (mast cell stabilizer), BRX-537A (a mast cell activator) and anti-NGF antibody. NMD did not modify colonic CRF level but increased colonic preproCRF expression and corticosteronaemia. Peripheral CRF, via CRF-R(1) receptor, but not corticosterone, was involved in the elevated GPP observed in these rats, through a mast-cell-mediated mechanism, since the increase of GPP induced by exogenous CRF was abolished by doxantrazole. Anti-NGF antibody treatment also reduced the elevated GPP induced by CRF or BRX-537A. CRF acts through CRF-R(1) receptors to stimulate NGF release from mast cells, which participates in the elevated GPP observed in NMD adult rats. This suggests that early traumatic experience induced neuro-endocrine dysfunction, involved in alterations of gut mucosal barrier.

Inhibition of Inflammatory Pain by CRF at Peripheral, Spinal and Supraspinal Sites: Involvement of Areas Coexpressing CRF Receptors and Opioid Peptides

There is conflicting evidence on the antinociceptive effects of corticotropin-releasing factor (CRF) along the neuraxis of pain transmission and the responsible anatomical sites of CRF's action at the level of the brain, spinal cord and periphery. In an animal model of tonic pain, that is, Freunds complete adjuvant (FCA) hindpaw inflammation, we systematically investigated CRF's ability to modulate inflammatory pain at those three levels of pain transmission by algesiometry following the intracerebroventricular, intrathecal, and intraplantar application of low, systemically inactive doses of CRF. At each level, CRF elicits potent antinociceptive effects, which are dose dependent and antagonized by local, but not systemic CRF receptor antagonist alpha-helical CRF indicating CRF receptor specificity. Consistently, we have identified by immunohistochemistry multiple brain areas, inhibitory interneurons within the dorsal horn of the spinal cord as well as immune cells within subcutaneous tissue--but not peripheral sensory neurons--that coexpress both CRF receptors and opioid peptides. In line with these anatomical findings, local administration of CRF together with the opioid receptor antagonist naloxone dose-dependently reversed CRF's antinociceptive effects at each of these three levels of pain transmission. Therefore, local application of low, systemically inactive doses of CRF at the level of the brain, spinal cord and periphery inhibits tonic inflammatory pain most likely through an activation of CRF receptors on cells that coexpress opioid peptides which results in opioid-mediated pain inhibition. Future studies have to delineate whether endogenous CRF at these three levels contributes to the body's response to cope with the stressful stimulus pain in an opioid-mediated manner.

A role for corticotropin-releasing factor, but not corticosterone, in acute food-deprivation-induced reinstatement of heroin seeking in rats

Acute 1-day food deprivation reinstates heroin seeking in rats via a leptin-dependent mechanism. However, leptin has no effect on footshock- or heroin-priming-induced reinstatement of drug seeking. These data may indicate that the neuronal systems underlying food-deprivation-induced reinstatement are dissociable from those involved in reinstatement induced by footshock stress. We used the reinstatement procedure to examine the roles of the adrenal stress hormone, corticosterone, and brain corticotropin-releasing factor (CRF) in acute food-deprivation-induced reinstatement of extinguished heroin seeking in rats. The rats were trained to press a lever for heroin (0.05-0.1 mg/kg/infusion, i.v.) for 10 days. Experiment 1: After heroin self-administration training, the rats were divided into two groups, which received either bilateral adrenalectomy surgery or sham surgery. Next, the rats were given 7-10 days of extinction training (during which lever presses were not reinforced with heroin). The rats were subsequently tested for reinstatement after acute (21 h) food deprivation. Experiment 2: After heroin self-administration and extinction training, the rats were tested for reinstatement induced by acute food deprivation. Before the test session, the rats were given intracerebroventricular injections of the CRF receptor antagonist alpha-helical CRF (0, 3, or 10 microg/rat). Adrenalectomy had no effect on the extinction behavior or acute food-deprivation-induced reinstatement of heroin seeking. The CRF receptor antagonist, alpha-helical CRF, dose-dependently blocked food-deprivation-induced reinstatement. The present data suggest that, as demonstrated for footshock-induced reinstatement of drug seeking, brain CRF, but not corticosterone, plays a critical role in acute food-deprivation-induced reinstatement of heroin seeking.

Rat tracheal epithelial responses to water avoidance stress

Psychologic stress has major effects on many organs and cellular systems. The hypothalamic-pituitary-adrenal axis, corticotropin-releasing factor (CRF), mast cells, and nerves have all been shown to be involved in intestinal epithelial responses to stress. There has been little information in the literature on stress and the lung. To investigate Wistar rat tracheal epithelial responses to acute water avoidance stress (1 hour). Tracheal tissue was examined in Ussing chambers. Increases in short-circuit current, but not in conductance, occurred after stress and were inhibited by previous injection of the CRF 1 and 2 receptor antagonist, alpha-helical CRF-(9-41). Electron microscopic morphologic evidence for tracheal mast cell activation and degranulation was found after stress. Stress and CRF injection both enhanced responses to substance P, but these effects were not inhibited by alpha-helical CRF. The data suggest that acute stress affects tracheal epithelium and sensitizes it to enhanced responses to substance P, partly through mast cell activation. Many but not all of these effects are mediated by CRF. These results offer the possibility that stress may be involved in inflammatory diseases of the lung such as asthma.

Role of withdrawal in reinstatement of morphine-conditioned place preference

Relapse is a major characteristic of drug addiction and the primary problem in treating drug abuse. Based on the negative reinforcement view of addiction, in which the motivation to take drugs is thought to result from the desire to avoid the aversive effect of drug withdrawal, it has been theorized that withdrawal symptoms play a major role in the maintenance of and relapse to drug taking. However, the role of withdrawal in relapse has not yet been systemically investigated in the reinstatement model. Using a conditioned place preference (CPP) paradigm, we examined the role of different morphine withdrawal states (spontaneous withdrawal, naloxone-precipitated withdrawal, and conditioned withdrawal) in relapse to drug seeking. Rats alternately received morphine (10 mg/kg, s.c.) and saline for 8 days to acquire the CPP. The morphine CPP disappeared after a 2-week extinction phase of saline-paired training. Rats were then chronically administered morphine to induce physical dependence. The different withdrawal states were induced and their roles in the reinstatement of extinguished CPP were assessed. During conditioned withdrawal, trunk blood samples were taken and the corticosterone level was measured by radioimmunoassay. To examine the role of corticotropin-releasing factor (CRF) receptor antagonist on conditioned-withdrawal-induced reinstatement of CPP, different doses of alpha-helical CRF (0.1 and 1 mug, i.c.v.) were administered 30 min prior to the CPP testing. The results show that morphine spontaneous withdrawal and naloxone-precipitated morphine withdrawal were ineffective in reinstatement morphine CPP. However, the withdrawal cues significantly elicited the reinstatement of CPP and increased corticosterone level. Moreover, pretreatment with the CRF receptor antagonist alpha-helical CRF (1 mug, i.c.v.) significantly attenuated the effects of withdrawal cues on reinstatement of CPP and corticosterone levels. These findings demonstrate that the cues associated with previous drug withdrawal play a major role in drug relapse and that activation of the CRF receptor is involved in conditioned-withdrawal-induced reinstatement. The present study suggests that CRF receptor antagonists might be of value in the treatment and prevention of relapse to drug seeking after long-term abstinence.

Effects of a chromogranin-derived peptide (CgA 47–66) in the writhing nociceptive response induced by acetic acid in rats

Chromogranin A (CgA) is an acidic protein identified within a large variety of endocrine cells. Colocalized with catecholamines in chromaffin cells, CgA is a prohormone precursor of small biologically active peptides. Vasostatin (CgA 1–76) is the most conserved fragment of CgA and chromogranin A 47–66 peptide (CgA 47–66) possesses potent antimicrobial activities. The aim of this study was to test the hypothesis that CgA 47–66 may be involved in mechanisms modulating nociception. Thus, we used acetic acid (AA) which produces a delayed inflammatory response and episodes of abdominal writhing, a marker of pain, when injected intraperitoneally (i.p.) to rats. Administration (i.p.) of CgA 47–66 induced specific opposite dose-dependent effects depending on concentration. That is, CgA 47–66 below 0.5 mg/kg produced antinociceptive effects, whereas at 2 mg/kg it produced a marked pronociceptive effect. The latter effect was blocked by diltiazem and indomethacin. CgA 47–66-induced antinociceptive effects on AA-induced responses were reversed when the corticotropin-releasing factor (CRF) antagonist alpha-helical CRF 9–41 was i.p. injected to animals prior to AA and CgA 47–66 administration. The administration of i.p. calcitonin gene-related peptide (CGRP) or substance P (SP) evoked dose-dependent abdominal writhing; this effect was abolished when CgA 47–66 was injected. The present data suggest, for the first time, that a fragment of CgA, CgA 47–66, possesses potent antinociceptive effects at low doses. Although the mechanism triggered by this peptide is unknown, CRF receptors are likely to be involved.

A Role for Corticotropin-Releasing Factor in Repeated Cold Stress-Induced Anxiety-Like Behavior during Forced Swimming and Elevated Plus-Maze Tests in Mice

SART (specific alternation of rhythm in temperature) stress is known to cause anxiety-like behavior in mice/rats in several anxiety-related behavioral tests. In the present study, we investigated possible roles for corticotropin-releasing factor (CRF) and glucocorticoids in SART stress-induced anxiety-like behavior in two different anxiety-related behavioral tests. In the forced swimming test, CRF, administered intracerebroventricular (i.c.v.) at 0.5-2 pmol/mouse, dose-dependently reduced immobility time in unstressed and SART-stressed mice. alpha-Helical CRF, a specific CRF receptor antagonist, administered i.c.v. at 0.1-1 nmol/mouse, dose-dependently increased immobility time in SART-stressed mice, but not in unstressed mice. In the elevated plus-maze test, CRF at 10-20 pmol/mouse significantly decreased the time spent in open arms in unstressed mice. CRF at a high dose tended to decrease this time in SART-stressed mice, but this decrease was not statistically significant. alpha-Helical CRF failed to modify the time in unstressed mice. In contrast, alpha-helical CRF at 0.38 and 0.75 nmol/mouse increased the time in SART-stressed mice. Both immobility time in the forced swimming test and time spent in open arms in the elevated plus-maze test in unstressed and SART-stressed mice were unaffected by adrenalectomy. These results suggest that CRF plays an important role in anxiety-like behavior caused by SART stress.

Corticotropin-releasing factor and interleukin-1beta are involved in the electroacupuncture-induced analgesic effect on inflammatory pain elicited by carrageenan.

Electroacupuncture (EA) is used to relieve various kinds of pain. However, the mechanistic basis of electroacupuncture analgesia (EAA) in inflammatory pain remains unclear. In the present study, we investigated whether endogenous peripheral corticotropin-releasing factor (CRF) or interleukin-1beta (IL-1) participated in EAA during hyperalgesia elicited by carrageenan-induced inflammation. Carrageenan was subcutaneously administered by intraplantar (i.pl.) injection of the left hind paw to induce inflammation. Nociceptive thresholds were measured using the paw pressure threshold (PPT) (Randall Sellito Test). Rats received 3 Hz EA in the left anterior tibial muscles for 1 hour after carrageenan injection. The selective CRF antagonist, alpha-helical CRF, or the recombinant IL-1 receptor antagonist, IL-1ra, was administered by i.pl. injection of the inflamed paw or by intravenous (i.v.) injection 1 hour before EA. PPT decreased significantly 3 hours after carrageenan injection. This decrease persisted at least 24 hours after carrageenan injection. EA resulted in significant increases of PPT, moreover, PPT elevations lasted 24 hours after carrageenan injection. By contrast, PPT elevations produced by EA were dose-dependently antagonized by local i.pl. injection of alpha-helical CRF or IL-1ra. This PPT elevation was not influenced by i.v. injection of alpha-helical CRF or IL-1ra. These findings suggest that peripheral CRF or IL-1 participate in EAA during hyperalgesia. The release of CRF or IL-1 elicited by EA may trigger the release of opioid peptides within inflamed tissue which may activate peripheral opioid receptors and inhibit the pain.