Corticotropin-releasing Factor In Mice Research Articles

Corticotropin-releasing factor is involved in acute stress-induced analgesia and antipruritus.

Under the condition of stress, the hypothalamic-pituitary-adrenal axis (HPA axis) is activated and causes the secretion of corticotropin-releasing factor (CRF). Previous studies have demonstrated that CRF is involved in the regulation of pain and itch. Thus, it remains worthy to explore whether the desensitization of pain and itch under high-intensity acute stress (such as high fear and tension) is related to the sharp increase of CRF. Forced swimming was used to simulate acute stress. ELISA and pharmacological methods were conducted to observe the effects of forced swimming on acute pain or itch and the relationship between blood CRF content and itch or pain behavior. Intracerebroventricular (ICV) administration of CRF was conducted to examine the effects of CRF on acute pain or itch. Intrathecal administration of CRF receptor agonist or antagonist was conducted to examine the receptor mechanisms of the regulatory role of CRF in pain and itch. ELISA experiment showed that the serum CRF in mice reached its peak within 5-10 min after acute stress (forced swimming). Behavioral data showed that the scratching behavior induced by itch agents decreased after acute swimming, while the mechanical pain threshold increased significantly. The inhibitory effect of acute stress on pain and itch is mediated by CRF receptor2 (CRFR2). Then, ICV injection of CRF was used to simulate the massive release of CRF under acute stress, and we observed that the scratching behavior induced by histamine or chloroquine was significantly inhibited after ICV injection of CRF. The above effects of CRF are mainly mediated by CRFR2. These results suggest that 5-10min after acute stress, a large amount of CRF is released into the blood from the hypothalamus, which significantly inhibits acute pain and itch by acting on CRFR2. ICV injection of CRF can replicate the antipruritus effects of acute stress. The present study investigated the mechanism of acute stress-induced analgesia and antipruritus and provided theoretical support for the treatment of pain and itch.

Formation of False Context Fear Memory Is Regulated by Hypothalamic Corticotropin-Releasing Factor in Mice.

Traumatic events frequently produce false fear memories. We investigated the effect of hypothalamic corticotropin-releasing factor (CRF) knockdown (Hy-Crf-KD) or overexpression (Hy-CRF-OE) on contextual fear memory, as fear stress-released CRF and hypothalamic–pituitary–adrenal axis activation affects the memory system. Mice were placed in a chamber with an electric footshock as a conditioning stimulus (CS) in Context A, then exposed to a novel chamber without CS, as Context B, at 3 h (B-3h) or 24 h (B-24h). The freezing response in B-3h was intensified in the experimental mice, compared to control mice not exposed to CS, indicating that a false fear memory was formed at 3 h. The within-group freezing level at B-24h was higher than that at B-3h, indicating that false context fear memory was enhanced at B-24h. The difference in freezing levels between B-3h and B-24h in Hy-Crf-KD mice was larger than that of controls. In Hy-CRF-OE mice, the freezing level at B-3h was higher than that of control and Hy-Crf-KD mice, while the freezing level in B-24h was similar to that in B-3h. Locomotor activity before CS and freezing level during CS were similar among the groups. Therefore, we hypothesized that Hy-Crf-KD potentiates the induction of false context fear memory, while Hy-CRF-OE enhances the onset of false fear memory formation.

Anxiogenic and antinociceptive effects induced by corticotropin-releasing factor (CRF) injections into the periaqueductal gray are modulated by CRF1 receptor in mice

Chemical or electrical stimulation of the dorsal portion of the midbrain periaqueductal gray (dPAG) produces anxiogenic and antinociceptive effects. In rats, chemical stimulation of dPAG by local infusion of the neuropeptide corticotropin-releasing factor (CRF) provokes anxiogenic effects in the elevated plus-maze test (EPM). CRF also produces antinociception when injected intracerebroventricularly in rats, however it remains unclear whether this response is also observed following CRF injection into the dPAG in mice. Yet, given that there are CRF1 and CRF2 receptor subtypes within the PAG, it is important to show in which receptor subtypes CRF exert its anxiogenic and antinociceptive effects in the dPAG. Here, we investigated the role of these receptors in the anxiogenic (assessed in the EPM) and antinociceptive (assessed by the Formalin test: 2.5% formalin injection into the right hind paw) effects following intra-dPAG infusion of CRF in mice. The results show that intra-dPAG injections of CRF (75pmol/0.1μl and 150pmol/0.2μl) produced dose-dependent anxiogenic and antinociceptive effects. In addition, local infusion of NBI 27914 (5-chloro-4-(N-(cyclopropyl)methyl-N-propylamino)-2-methyl-6-(2,4,6-trichlorophenyl)-aminopyridine; 2nmol/0.2μl), a CRF1 receptor antagonist, completely blocked both the anxiogenic and antinociceptive effects induced by local infusion of CRF, while that of antisauvagine 30 (ASV30; 1nmol/0.2μl), a CRF2 receptor antagonist, did not alter the CRF effects. Present results are suggestive that CRF1 (but not CRF2) receptors play a crucial role in the anxiogenic and antinociceptive effects induced by CRF in the dPAG in mice.

Corticotropin-Releasing Factor-Overexpressing Mice Exhibit Reduced Neuronal Activation in the Arcuate Nucleus and Food Intake in Response to Fasting

Corticotropin-releasing factor (CRF) overexpressing (OE) mice are a genetic model that exhibits features of chronic stress. We investigated whether the adaptive feeding response to a hypocaloric challenge induced by food deprivation is impaired under conditions of chronic CRF overproduction. Food intake response to a 16-h overnight fast and ip injection of gut hormones regulating food intake were compared in CRF-OE and wild type (WT) littermate mice along with brain Fos expression, circulating ghrelin levels, and gastric emptying of a nonnutrient meal. CRF-OE mice injected ip with saline showed a 47 and 44% reduction of 30-min and 4-h cumulative food intake response to an overnight fast, respectively, compared with WT. However, the 30-min food intake decrease induced by ip cholecystokinin (3 microg/kg) and increase by ghrelin (300 microg/kg) were similar in CRF-OE and WT mice. Overnight fasting increased the plasma total ghrelin to similar levels in CRF-OE and WT mice, although CRF-OE mice had a 2-fold reduction of nonfasting ghrelin levels. The number of Fos-immunoreactive cells induced by fasting in the arcuate nucleus was reduced by 5.9-fold in CRF-OE compared with WT mice whereas no significant changes were observed in other hypothalamic nuclei. In contrast, fasted CRF-OE mice displayed a 5.6-fold increase in Fos-immunoreactive cell number in the dorsal motor nucleus of the vagus nerve and a 34% increase in 20-min gastric emptying. These findings indicate that sustained overproduction of hypothalamic CRF in mice interferes with fasting-induced activation of arcuate nucleus neurons and the related hyperphagic response.

Fractal rigidity by enhanced sympatho-vagal antagonism in heartbeat interval dynamics elicited by central application of corticotropin-releasing factor in mice

The dynamics of heartbeat interval fluctuations were studied in awake unrestrained mice following intracerebroventricular application of the neuropeptide corticotropin-releasing factor (CRF). The cardiac time series derived from telemetric ECG monitoring were analyzed by non-parametric techniques of nonlinear signal processing: delay-vector variance (DVV) analysis, higher-order variability (HOV) analysis, empirical mode decomposition (EMD), multiscale embedding-space decomposition (MESD), multiexponent multifractal (MEMF) analysis. The analyses support the conjecture that cardiac dynamics of normal control mice has both deterministic and stochastic elements, is nonstationary, nonlinear, and exerts multifractal properties. Central application of CRF results in bradycardia and increased variability of the beat-to-beat fluctuations. The altered dynamical properties elicited by CRF reflect a significant loss of intrinsic structural complexity of cardiac control which is due to central neuroautonomic hyperexcitation, i.e., enhanced sympatho-vagal antagonism. The change in dynamical complexity is characterized by an effect referred to as fractal rigidity, leading to a significant impairment of adaptability to extrinsic challenges in a fluctuating environment. The impact of dynamical neurocardiopathy as a major precipiting factor for the propensity of cardiac arrhythmias or sudden cardiac death by unchecked central CRF release in significant acute life events in man is critically discussed.

NMR structure and peptide hormone binding site of the first extracellular domain of a type B1 G protein-coupled receptor.

The corticotropin-releasing factor (CRF) ligand family has diverse effects on the CNS, including the modulation of the stress response. The ligands' effects are mediated by binding to CRF G protein-coupled receptors. We have determined the 3D NMR structure of the N-terminal extracellular domain (ECD1) of the mouse CRF receptor 2beta, which is the major ligand recognition domain, and identified its ligand binding site by chemical-shift perturbation experiments. The fold is identified as a short consensus repeat (SCR), a common protein interaction module. Mutagenesis reveals the integrity of the hormone-binding site in the full-length receptor. This study proposes that the ECD1 captures the C-terminal segment of the ligand, whose N terminus then penetrates into the transmembrane region of the receptor to initiate signaling. Key residues of SCR in the ECD1 are conserved in the G protein-coupled receptor subfamily, suggesting the SCR fold in all of the ECD1s of this subfamily.

Molecular cloning and functional expression of the mouse CRF 2(a) receptor splice variant

The mouse corticotropin-releasing factor (CRF) type 2a receptor (CRF 2(a)) splice variant was cloned by a PCR-based approach. The corresponding cDNA was found to encode a 411-amino acid polypeptide with highest sequence homology to the rat CRF 2(a) receptor. By semiquantitative reverse transcriptase PCR (RT-PCR) analysis, the CRF 2(b) mRNA was mainly found in the heart and skeletal muscle with only low level expression in the brain. In contrast, CRF 2(a) mRNA was restricted to the brain with major expression sites in the cortex, hippocampus, hypothalamus and telencephalon. Binding and cyclic AMP stimulation studies showed a similar ligand selective profile for both mCRF 2 receptor splice variants. A notable exception however, was urotensin I which displayed a ∼3-fold higher affinity for the CRF 2(a) receptor and also stimulated cyclic AMP production in mCRF 2(a)-transfected cells with a ∼3-fold higher potency than in mCRF 2(b)-transfected cells. These data show that the mouse like other mammalian species expresses two ligand-selective CRF 2 receptor splice variants and that the mCRF 2(a) receptor is the predominant central CRF 2 receptor in the mouse.

Development of a selective photoactivatable antagonist for corticotropin-releasing factor receptor, type 2 (CRF2).

A novel photoactivatable analog of antisauvagine-30 (aSvg-30), a specific antagonist for corticotropin-releasing factor (CRF) receptor, type 2 (CRF2), has been synthesized and characterized. The N-terminal amino-acid d-Phe in aSvg-30 [d-Phe11,His12]Svg(11-40) was replaced by a phenyldiazirine, the 4-(1-azi-2,2,2-trifluoroethyl)benzoyl (ATB) residue. The photoactivatable aSvg-30 analog ATB-[His12]Svg was tested for its ability to displace [125I-Tyr0]oCRF or [125I-Tyr0]Svg from membrane homogenates of human embryonic kidney (HEK) 293 cells stably transfected with cDNA coding for rat CRF receptor, type 1 (rCRF1) or mouse CRF receptor, type 2beta (mCRF2beta). Furthermore, the ability of ATB-[His12]Svg(12-40) to inhibit oCRF- or Svg-stimulated cAMP production of transfected HEK 293 cells expressing either rCRF1 (HEK-rCRF1 cells) or mCRF2beta (HEK-mCRF2beta cells) was determined. Unlike astressin and photo astressin, ATB-[His12]Svg(12-40) showed high selective binding to mCRF2beta (Ki = 3.1 +/- 0.2 nm) but not the rCRF1 receptor (Ki = 142.5 +/- 22.3 nm) and decreased Svg-stimulated cAMP activity in mCRF2beta-expressing cells in a similar fashion as aSvg-30. A 66-kDa protein was identified by SDS/PAGE, when the radioactively iodinated analog of ATB-[His12]Svg(12-40) was covalently linked to mCRF2beta receptor. The specificity of the photoactivatable 125I-labeled CRF2beta antagonist was demonstrated with SDS/PAGE by the finding that this analog could be displaced from the receptor by antisauvagine-30, but not other unrelated peptides such as vasoactive intestinal peptide (VIP).

Secondary structure of antisauvagine analogues is important for CRF receptor antagonism: development of antagonists with increased potency and receptor selectivity

Antisauvagine-30 (aSVG) is the only high-affinity antagonist for the corticotropin-releasing factor (CRF) type 2 (CRF 2) receptor. A structure–activity relationship study was performed to pinpoint residues conferring aSVG’s selectivity. The aSVG-analogues being N-terminally extended by one or two residues or containing the Ala 22Arg 23Ala 24 (ARA-motif) of CRF, were synthesized. Additionally, a lactam bridge between positions 29 and 32 was introduced. The modified peptides were analyzed for α-helicity properties, binding affinities and antagonistic potencies at the rat CRF 1 and mouse CRF 2B receptors. While N-terminal prolongation and replacement of d-Phe 11 by Tyr 11 increased the affinity for the CRF 2 receptor, the introduction of the ARA motif resulted in a loss of CRF 2 receptor selectivity. These data show that aSVG 10–40 analogues are more potent CRF 2 receptor antagonists than aSVG 11–40 peptides, while introduction of the ARA-motif or a cyclic constraint between residues 29 and 32 favors binding to the CRF 1 receptor.

125I-Antisauvagine-30: a novel and specific high-affinity radioligand for the characterization of corticotropin-releasing factor type 2 receptors

Corticotropin-releasing factor (CRF) receptors type 1 (CRF 1) and type 2 (CRF 2) differ from each other in their pharmacological properties. The human and ovine CRF versions bind to CRF 1 receptors with significantly higher affinity than to CRF 2 receptors. Recently antisauvagine-30, an N-terminally truncated version of the CRF analog sauvagine, was characterized as a specific antagonist to mouse CRF 2B. We have synthesized the radiolabeled version 125I-antisauvagine-30 and tested it for its affinity at human CRF 1 (hCRF 1), hCRF 2A, Xenopus CRF 1 (xCRF 1) and xCRF 2 receptors. In control binding studies 125I-labeled hCRF, sauvagine and astressin were also bound to these receptors. 125I-antisauvagine-30 exclusively bound to hCRF 2A and xCRF 2 but not to hCRF 1 and xCRF 1 receptors. 125I-antisauvagine-30 binding to hCRF 2A and xCRF 2 receptors was saturable and of high affinity (hCRF 2A: K d=125 pM; xCRF 2: K d=1.1 nM). In displacement binding experiments using 125I-antisauvagine-30 as radioligand several CRF analogs bound to hCRF 2A and xCRF 2 receptors with similar rank orders as reported with other CRF radioligands. Finally, preliminary studies using 125I-antisauvagine-30 binding to membrane homogenates prepared from different rat brain structures showed that the peptide bound specifically to brain areas expressing CRF 2 receptors. These data demonstrate that 125I-antisauvagine-30 is the first high-affinity ligand to specifically label CRF 2 receptors.

Intracerebroventricularly administered corticotropin-releasing factor inhibits food intake and produces anxiety-like behaviour at very low doses in mice.

Previous studies have demonstrated that corticotropin-releasing factor (CRF) produces behavioural, physiological and immunological responses similar to those induced by stress. However, these findings have been validated largely in laboratory rats. We examined the effects of intracerebroventricular (i.c.v.) administration of CRF on anxiety and food intake in mice. Using the elevated-plus maze, we measured anxiety levels after i.c.v. CRF in mice. We also measured food intake for 2 h after i.c.v. CRF. CRF increased the normal preference for the closed arms of the maze at a very low dose of 3 pmol, indicating an anxiogenic effect. CRF powerfully suppressed food intake at the doses of 3-300 pmol for over 2 h. Our results demonstrate that i.c.v. CRF evokes anxiogenic behaviour and suppresses feeding with the same dose-response relationships in mice. CRF may thus play a role in integrating the overall responses to stress through co-ordinated actions in the brain of this species.

Signaling properties of mouse and human corticotropin-releasing factor (CRF) receptors: decreased coupling efficiency of human type II CRF receptor.

CRF is the primary neuroregulator of the function of the hypothalamic-pituitary-adrenal axis. We have recently cloned a mouse CRF receptor (mCRF-R) complementary DNA (cDNA) from an AtT-20 cell cDNA library by polymerase chain reaction. To compare the functions of mCRF-R to those of the human type I and type II CRF receptors (hCRF-RI and hCRF-RII), cDNAs were cloned into the expression vector pcDNA1 and transfected into COS-7 cells. CRF binding and CRF-stimulated cAMP accumulation as well as phosphoinositide hydrolysis were measured. Scatchard analysis of the binding of 125I-labeled [Tyr0]r/hCRF ([125I]CRF) to COS-7 cells expressing mCRF-R and hCRF-RI cDNAs revealed the same apparent Kd (9 nM). In contrast, the apparent binding Kd for hCRF-RII was 20 nM CRF. Maximal stimulatory concentrations (1 microM) of rat/human CRF-(1-41) (r/hCRF) increased cAMP accumulation in COS-7 cells transfected with mCRF-R, hCRF-RI, and hCRF-RII cDNA plasmid (10 micrograms each) from basal values of 8-19 pmol/10(5) cells.15 min to 84 +/- 10, 87 +/- 16, and 45 +/- 16 pmol/10(5) cells.15 min, respectively. The EC50 values of r/hCRF-stimulated cAMP accumulation in COS-7 cells expressing mCRF-R and hCRF-RI cDNAs were similar at 0.4 +/- 0.2 and 0.7 +/- 0.2 nM, respectively. Conversely, the EC50 of r/hCRF-stimulated cAMP accumulation in hCRF-RII-transfected COS-7 cells was 47.5 +/- 18.9 nM. As the level of expression of hCRF-RII was lower than that of hCRF-RI, we compared r/hCRF-stimulated cAMP accumulation in COS-7 cells expressing low and high levels of hCRF-RI. The EC50 for r/hCRF-stimulated cAMP accumulation in COS-7 cells transfected with hCRF-RI did not change when receptor expression was varied by a factor of 1- to 8.4-fold. In contrast, the EC50 for r/hCRF-stimulated cAMP accumulation mediated by hCRF-RII was at least 100-fold higher than that mediated by the hCRF-RI in COS-7 cells, which suggests poor coupling between hCRF-RII and adenylate cyclase. Inositol phosphate (IP) levels were also determined in mCRF-R, hCRF-RI, and hCRF-RII cDNA-transfected COS-7 cells stimulated with increasing concentrations of r/hCRF. r/hCRF-stimulated IPs accumulation was dose dependent in COS-7 cells expressing mCRF-R and hCRF-RI using 100 and 1000 nM r/hCRF. Concentrations of 10 (or less) nM r/hCRF had no effect on IP generation. hCRF-RII did not mediate stimulation of IP even at 1000 nM r/hCRF.(ABSTRACT TRUNCATED AT 400 WORDS)

Overproduction of corticotropin-releasing factor in transgenic mice: a genetic model of anxiogenic behavior

Corticotropin-releasing factor (CRF) is released in response to various stressors and regulates adrenocorticotropin secretion and glucocorticoid production. In addition to its endocrine functions, CRF acts as a neuromodulator in extra-hypothalamic systems and has been shown to play a role in behavioral responses to stress. CRF overproduction has been implicated in affective disorders such as depression and anorexia nervosa. A transgenic mouse model of CRF overproduction has been developed in order to examine the endocrine and behavioral effects of chronic CRF excess. CRF transgenic animals exhibit endocrine abnormalities involving the hypothalamic-pituitary-adrenal axis such as elevated plasma levels of ACTH and glucocorticoids. The present series of experiments tested the hypothesis that chronic overproduction of CRF throughout the life-span of these animals may lead to an anxiogenic behavioral state. CRF transgenic mice and normal littermate controls were tested by measuring locomotor activity in a novel environment and through the use of an elevated plus-maze as indices of anxiety. CRF transgenic animals exhibited an increase in anxiogenic behavior, an effect known to occur following central administration of CRF in mice and rats. Injection of the CRF antagonist alpha-helical CRF 9-41 into the lateral cerebral ventricles reversed the anxiogenic state observed in the CRF transgenics. This finding supports the possibility that central CRF overproduction may mediate the anxiogenic behavior exhibited in this animal model. Thus, CRF transgenic mice represent a genetic model of CRF overproduction that provides a valuable tool for investigating the long-term effects of CRF excess and dysregulation in the CNS.

The Zucker fatty (fa) gene is not a mutation of corticotropin-releasing factor

Corticotropin-releasing factor (CRF) appears to regulate several physiological systems that display prominent abnormalities in Zucker fatty (fa/fa) rats, including the hypothalamic-pituitary-adrenal axis, the autonomic nervous system, and feeding behavior. Moreover, central administration of CRF ameliorates the obese phenotype. In light of these observations, the gene for CRF is a plausible candidate for the defective gene in the Zucker fatty rat. We report here the use of molecular genetic linkage analysis to test the hypothesis that fa is a mutant allele of the CRF gene. A restriction fragment length polymorphism for CRF between Zucker (13M) and Brown Norway (BN) DNA allowed us to examine segregation of 13M and BN CRF alleles relative to fa in 58 obese (fa/fa) F2 progeny of a 13MBN fa/+F1 intercross. If fa = CRF, all animals homozygous for the fatty mutation should be homozygous for the 13M CRF allele. However, only 10/58 fa/fa animals were homozygous for the 13M CRF allele, indicating that fa and CRF are not allelic. Thus, although CRF may be important in the physiology of Zucker rat obesity, fa is not a CRF mutation. Using a mouse C57BL/6J Spretus F1 x C57BL DBA/2J F1 intercross, we were able to demonstrate that the mouse CRF gene is linked to the carbonic anhydrase II (Car-2) gene on mouse chromosome 3, in a region of synteny-homology with rat chromosome 2. Thus the rat CRF gene is probably located on chromosome 2.

Stimulation by corticotropin-releasing factor of the release of immunoreactive dynorphin A from mouse spinal cords in vitro

Corticotropin-releasing factor (CRF) has been shown to release endogenous opioid peptides from several rat brain regions. Since we have demonstrated previously that the actions produced by intrathecally administered CRF in mice involve spinal κ opioid receptors, experiments were conducted in this study to test the possibility that CRF may release dynorphin A, a putative endogenous κ opioid agonist, from the mouse spinal cord. Using a superfusion system in vitro, mouse spinal cords were superfused with aerated (95% O 2, 5% CO 2) Krebs-Ringer buffer. Fractions of superfusion were collected and dynorphin A levels in each fraction were monitored by radioimmunoassay. The presence of CRF in the perfusion buffer stimulated significantly the release of immunoreactive dynorphin A. The releasing rate of immunoreactive dynorphin A returned to the basal level after withdrawing CRF from the superfusion buffer. The stimulatory effect of CRF on the release of immunoreactive dynorphin A was abolished by a-helical CRF-(9–41), a CRF receptor antagonist, indicating that the dynorphin-releasing effect of CRF was mediated by CRF receptors in the spinal cord. Also the dynorphin-releasing effect of CRF was a concentration-related phenomenon, with an estimated EC 50 value of 5.3 nM. The results from this study support the hypothesis that intrathecally administered CRF may produce its effects by releasing endogenous dynorphin from the terminals of dynorphin-containing neurons in the spinal cord. This study also provides evidence to support the notion that there is a close communication between CRF- and opioid peptide-containing neuronal pathways in the central nervous system.

Involvement of spinal kappa opioid receptors in the antiociception produced by intrathecaliy administered corticotropin-releasing factor in mice

Involvement of spinal kappa opioid receptors in the antiociception produced by intrathecaliy administered corticotropin-releasing factor in mice

Gastrointestinal motor effects of corticotropin-releasing factor in mice

The present investigation examined the effects of centrally and peripherally administered corticotropin-releasing factor on gastric emptying and gastrointestinal transit in mice. Corticotropin-releasing factor, given either intracerebroventricularly or intrathecally, caused a dose-dependent inhibition of gastric emptyping and gastrointestinal transit. Intravenous or intraperitoneal administration of corticotropin-releasing factor, while 5- to 7-fold less potent than after central injection, produced an equivalent level of effect. α-Helical corticotropin-releasing factor 9–41, a corticotropin-releasing factor receptor antagonist, blocked the effects of intracerebroventricularly administered corticotropin-releasing factor when the antagonist was given concurrently by the intracerebroventricular, but not by the intraperitoneal, route. Conversely, corticotropin-releasing factor, when given peripherally, was antagonized equally well by intracerebroventricular or intraperitoneal administration of the antagonist. The inhibition of gastric emptying induced by corticotropin-releasing factor was reduced by pretreatment with the ganglionic blocking agent, chlorisondamine, and in adrenalectomized mice, but this effect was not antagonized by naloxone. These findings provide evidence for an action of corticotropin-releasing factor within the central nervous system, as well as a peripheral site of action, to inhibit gastric emptying in the mouse. The gastrointestinal motor effects of corticotropin-releasing factor are not mediated through opioid mechanisms although their full expression may require intact autonomic innervation and adrenal function.

The hippocampus and amygdala mediate the locomotor stimulating effects of corticotropin-releasing factor in mice

We have previously demonstrated that both stress manipulations and corticotropin-releasing factor (CRF) elevate locomotor activity in mice primarily in the center region of an open field. In the present study, other than confirming these findings, we have further examined the roles of the dentate gyrus of the hippocampus, the amygdala, and the caudate nucleus in mediating the locomotor-stimulating effect of CRF. Results indicate that among the areas examined, the hippocampus is the most important neural substrate of the action of CRF. The amygdala is also partly responsible for the behavioral effect produced by CRF. The caudate nucleus, however, although is important in the expression of gross motor activity, is not involved in the effect of CRF on locomotion in mice. The results are compared with those obtained in rats and are discussed in terms of the interactions between CRF and stress.