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The aim of our study was to determine the role of corticotropin-releasing factor (CRF), the urocortins (Ucn1, Ucn2 and Ucn3) and their receptors (CRF 1 and CRF 2 ) in the sociability of mice. Male CFLP mice were administered intracerebroventricularly (icv) with CRF and urocortins alone or in combination with antalarmin (specific CRF 1 antagonist) and astressin 2B (specific CRF 2 antagonist) and then investigated in a Crawley social interaction test arena, that consists of three chambers. An unknown male in a cage was put in the first chamber and an empty cage was put in the opposite chamber. The tested male was habituated with the middle chamber for 5min and then allowed to explore the remaining chambers for 5min, during which the number of entries and the time of interaction were measured. Intracerebroventricular administration of CRF decreased significantly the number of entries and the time of interaction with the unknown male and these effects were blocked by antalarmin, but not astressin 2B . In contrast, central administration of Ucn1 increased significantly the number of entries into the chamber of the unknown male, without changing the time of interaction and this effect was blocked by astressin 2B , but not antalarmin. Central administration of Ucn2 and Ucn3 didn't influence remarkably the number of entries, but it reduced the time of interaction between the male mice. Our study suggests that CRF and Ucn1 may play important, but different roles in sociability, and that Ucn2 and Ucn3, playing similar roles, must be also involved in social interactions., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The aim of the present study was to determine the role of corticotropin-releasing factor (CRF), the urocortins (UCN 1, UCN 2 and UCN 3) and their receptors (CRF 1 and CRF 2 ) in the preference for social novelty of mice. Male CFLP mice were administered intracerebroventricularly (ICV) with CRF, UCN 1, UCN 2 or UCN 3 and/or antalarmin or astressin 2B, selective antagonists of CRF 1 receptor and CRF 2 receptor, respectively. The mice were investigated in a Crawley social interaction test arena consisting of three chambers: an unknown female was set in the first chamber and a known female, with which the male was familiarized previously for 24h, was set in the third chamber. First the tested male was habituated with the middle chamber for 5min and then allowed to explore the remaining chambers for 5min, during which the number of entries and the time of interaction were measured. CRF decreased significantly the number of entries and the time of interaction with the unknown female, but not the known female. UCN 1 decreased significantly the number of entries into the chamber of the unknown female, but not the known female, without changing the time of interaction. All decreasing effects were reversed by antalarmin, but not astressin 2B. UCN 2 and UCN 3 didn't influence significantly any of the parameters. The present study suggests that CRF and UCN 1 decrease the preference for social novelty by activating CRF 1 receptor, while UCN 2 and UCN 3, activating selectively CRF 2 receptor, do not participate to male-female interaction., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Amnesia is a deficit in memory caused by brain damage, disease, or trauma. Until now, there are no successful medications on the drug market available to treat amnesia. Short analogs and mimetics of human urocortin 3 (Ucn 3) tripeptide were synthetized and tested for their action against amnesia induced by eletroconvulsion in mice. Among the 16 investigated derivatives of Ucn 3 tripeptide, eight compounds displayed antiamnesic effect. Our results proved that the configuration of chiral center of glutamine does not affect the antiamnesic properties. Alkyl amide or isoleucyl amide at the C-terminus may lead to antiamnesic compounds. As concerned the N-terminus, acetyl, Boc, and alkyl ureido moieties were found among the active analogs, but the free amino function at the N-terminus usually led to an inactive derivatives. These observations may lead to the design and synthesis of small peptidomimetics and amino acid derivatives as antiamnesic drug candidates, although the elucidation of the mechanism of the action requires further investigations.

Corticotropin-releasing factor (CRF) is a hypothalamic neurohormone and an extrahypothalamic neurotransmitter that regulates the hypothalamic-pituitary-adrenal (HPA) axis. The urocortins (UCN I, UCN II and UCN III) are CRF-related peptides, which may also regulate the HPA axis directly or indirectly, by modulation of extrahypothalamic neurotransmitters, such as amygdalar GABA and hippocampal glutamate. Our previous in vitro superfusion studies have already demonstrated that CRF and UCN I stimulate the amygdalar GABA release in rats. The aim of the present study was to investigate the effects of CRF, UCN I, UCN II and UCN III on the glutamate release elicited electrically from rat hippocampal slices in similar in vitro conditions. In order to investigate the participation of CRF receptors (CRFR1 and CRFR2) in this process, hippocampal slices were pretreated with antalarmin, a selective antagonist of CRFR1 or astressin 2B, a selective antagonist of CRFR2. CRF and UCN I at 100 nM decreased significantly the hippocampal glutamate release evoked by electrical stimulation. In contrast, 100 nM of UCN II and UCN III did not affect significantly the hippocampal glutamate release enhanced by electrical stimulation. The decreasing effects of CRF and UCN I were reversed by antalarmin, but not by astressin 2B, both being administered in equimolar doses. Our results demonstrate that CRF and UCN I inhibit the glutamate release in the hippocampus via CRFR1 and that CRFR2 does not participate to this process. Based on the previous and the present results we conclude that CRFR1 agonists can activate the HPA axis not only directly, but also indirectly by increasing the amygdalar GABA release and decreasing the hippocampal glutamate release., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Peptide analogs of urocortin 3[36–38] (Ucn 3[36–38]), obtained with deletion or replacement of amino acids of the original human urocortin 3 sequence, were designed, synthesized, and tested in vivo for treatment of depression. Based on the results of the biological tests of the peptide analogs, several new peptidomimetics of the above short analogs of urocortin 3, including urea- and azapeptides, were also designed and synthesized and found to preserve the antidepressant-like effect of the 38 amino acid long original neuropeptide. The molecular modifications of urocortin 3[36–38] led to an improved understanding of the relationship between molecular structure and biological activity of this peptide, and the novel peptidomimetics could be further tested for possible clinical treatment of depression.

Urocortin 3 (Ucn 3) was found to impair passive avoidance learning in male and female mice. The possible involvement of transmitters in the action, the animals were pretreated with the following receptor antagonists in doses which alone could not influence the measurement. Haloperidol (a D2, dopamine receptor antagonist), phenoxybenzamine (a nonselective α1-adrenergic receptor antagonist), atropine (a nonselective muscarinic acetylcholine receptor antagonist), bicuculline (a γ-aminobutyric acid subunit A receptor antagonist), nitro-L-arginine (a nitric oxide synthase inhibitor), antalarmin (a CRF1 receptor antagonist) and astressin 2B (a CRF2 receptor antagonist). Haloperidol, phenoxybenzamine, bicuculline, atropine, nitro-L-arginine and astressin 2B prevented the action of Ucn 3, in both sexes, whereas antalarmin exerted no action in either male or female animals., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Urocortin II (Ucn II) and Urocortin III (Ucn III) are selective agonists of the CRF receptor type 2 (CRFR2). The aim of the present experiments was to investigate the effects of Ucn II and Ucn III on the central CRF and peripheral glucocorticoids in rats. Increasing doses (0.5-1-2-5 μg/2 μl) of Ucn II or Ucn III were administered intracerebroventricularly, then CRF concentration was determined by immunoassays in two different brain regions, the amygdala and the hypothalamus, and in two different time paradigms, 5 and 30 min after the administration of peptides. In parallel with the second determination, plasma corticosterone concentration was measured by chemofluorescent assay. The amygdalar CRF amount was increased significantly by 0.5 and 5 μg of UCN II and 2 and 5 μg of UCN III in the 5 min experiments and by 5 μg of UCN II and 0.5 and 5 μg of UCN III in the 30 min experiments. The hypothalamic CRF content was not affected considerably in the 5 min paradigm, but it was influenced significantly in the 30 min paradigm, with 0.5 and 1 μg of UCN II and 0.5-2 μg of UCN III decreasing, and 2 and 5 μg of UCN II and 5 μg of UCN III increasing the hormone concentration, respectively. The plasma corticosterone concentration was decreased by 1 and 2 μg of UCN II and UCN III and increased by 0.5 and 5 μg of UCN III. The present results demonstrate that central administration of Ucn II and Ucn III modulate time-dependently and dose-dependently the amygdalar and the hypothalamic CRF concentration, and, directly or indirectly, the plasma corticosterone concentration. The present experiments suggest that the role of CRFR2 in the regulation of the HPA axis can be inhibitory or stimulatory, depending on the actual concentration of their agonists., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Corticotropin-releasing factor (CRF) and the urocortins (UCNs) are structurally and pharmacologically related neuropeptides which regulate the endocrine, autonomic, emotional and behavioral responses to stress. CRF and UCN1 activate both CRF receptors (CRFR1 and CRFR2) with CRF binding preferentially to CRFR1 and UCN1 binding equipotently to both receptors. UCN2 and UCN3 activate selectively CRFR2. Previously an in vitro study demonstrated that superfusion of both CRF and UCN1 elevated the GABA release elicited by electrical stimulation from rat amygdala, through activation of CRF1 receptors. In the present experiments, the same in vitro settings were used to study the actions of CRF and the urocortins on hypothalamic GABA release. CRF and UCN1 administered in equimolar doses increased significantly the GABA release induced by electrical stimulation from rat hypothalamus. The increasing effects of CRF and UCN1 were inhibited considerably by the selective CRFR1 antagonist antalarmin, but were not influenced by the selective CRFR2 antagonist astressin 2B. UCN2 and UCN3 were ineffective. We conclude that CRF1 receptor agonists induce the release of GABA in the hypothalamus as well as previously the amygdala. We speculate that CRF-induced GABA release may act as a double-edged sword: amygdalar GABA may disinhibit the hypothalamic CRF release, leading to activation of the hypothalamic-pituitary-adrenal axis, whereas hypothalamic GABA may inhibit the hypothalamic CRF release, terminating this activation., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

In the present experiments, the anxiolytic action of Ucn 3 fragments were studied in an elevated plus maze in mice following icv administration in an attempt to identify the biologically active center of the molecule. Ucn 3, Ucn 3 (18-38), Ucn 3 (19-27), Ucn 3 (28-38), Ucn 3 (34-38), and Ucn 3 (36-38) but not Ucn 3 (34-36), demonstrated anxiolytic action by increasing the time the mice spent in open arms, and Ucn 3 and Ucn 3 (34-38) did so by increasing the number of entries into open arms. The shortest molecule which elicited anxiolytic effects was the tripeptide Ucn 3 (36-38), H-Ala-Gln-Ile-NH(2). The results indicate that the total sequence of Ucn 3 is not necessary for the anxiolytic action of Ucn 3. Establishment the smallest active sequence of Ucn 3 will allow the synthesis of analogs or mimetics for anxiolytic action., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Corticotropin-releasing factor (CRF) is the major neuromodulator of the hypothalamic-pituitary-adrenal axis, regulating the behavioural, endocrine, autonomic and immune responses to stress. Together with the recently discovered members of the CRF peptide family, urocortin 1, urocortin 2 and urocortin 3, it also has neurotransmitter actions. Previous publication has demonstrated that stress induces CRF release in the paraventricular nucleus of the hypothalamus and the release of both CRF and GABA in the amygdala. Accordingly, the aim of the present study was to determine the effects of the members of the CRF peptide family on GABA release from the amygdala by using an in vitro superfusion system. In order to study the participation of different CRF receptors (CRF1 and CRF2) in this process, rat amygdalar slices were pretreated with selective CRF1 and CRF2 antagonists. CRF and urocortin 1 significantly increased the release of [(3)H]GABA from the slices following electrical stimulation, whereas urocortin 2 and urocortin 3 were ineffective. The actions of CRF and urocortin 1 were blocked by the selective CRF1 receptor antagonist antalarmin, but were not inhibited by the selective CRF2 receptor antagonist astressin 2B, both administered in equimolar doses. Our results demonstrate that the release of GABA from the amygdala is mediated by CRF and urocortin 1 through the activation of CRF1 receptors.

The actions of individual urocortins on colon temperature were studied in rats. Urocortin 1, urocortin 2 or urocortin 3 was injected into the lateral brain ventricle in conscious rats and the colon temperature was measured at different times following injection, for up to 6 h. In order to study the possible role of prostaglandins, the animals were treated with either a urocortin together with the pyrazolone derivative noraminophenazone to inhibit the action of cyclooxygenase in initiating hyperthermia, or with noraminophenazone 30 min following urocortin administration to act on existing hyperthermia. Noraminophenazone was administered intramuscularly in a dose of 50 mg/kg. Urocortin 1 caused a dose-related increase in colon temperature, maximal action being observed at a dose of 2 microg with the maximal increase in body temperature at 4 h. Noraminophenazone prevented the urocortin-induced increase in colon temperature and attenuated the already existing elevated body temperature. Somewhat similar action was observed with urocortin 2. However, following treatment with 0.5 or 1.0 microg urocortin 2, the action was already over at 2 h, whereas 2 microg increased the colon temperature steadily, with a maximum at 4 h. Noraminophenazone blocked or diminished the action of urocortin 2. Urocortin 3 in a dose of 1 microg was the most effective in increasing the colon temperature; the maximal effect was observed at 2 h. Noraminophenazone blocked the development of urocortin 3-induced hyperthermia, or attenuated it when the hyperthermia was already present. The results demonstrated that urocortin 1, 2 or 3 caused increases in body temperature when injected into the lateral brain ventricle, though the optimal dose and the duration of hyperthermia differed for the individual urocortins. The cyclooxygenase inhibitor blocked or diminished the action of these urocortins, indicating the involvement of prostaglandins in urocortin-induced hyperthermia.

The members of the CRF peptide family, corticotropin-releasing factor (CRF), urocortin I (Ucn I), urocortin II (Ucn II) and urocortin III (Ucn III) coordinate endocrine and behavioral responses to stress. CRF has also been demonstrated to stimulate dopamine (DA) synthesis. In our study, a superfusion system was used to investigate the effects of this peptide family on striatal DA release following electrical stimulation. The involvement of the CRF receptors was studied by pretreatment of rat striatal slices with selective CRF antagonists. CRF and Ucn I increased the release of [(3)H]DA while Ucn II and Ucn III were ineffective. The CRFR1 antagonist antalarmin inhibited the [(3)H]DA release induced by electrical stimulation and enhanced by CRF and Ucn I. The CRFR2 antagonist astressin-2B was ineffective. These results suggest that CRF and Ucn I mediate DA release through the activation of CRFR1. Ucn II and Ucn III are not involved in this process.

The action of urocortin on one-way passive avoidance learning was tested in mice. Urocortin was administered into the lateral brain ventricle and the latency of the passive avoidance response was measured 24 h later. For study of the roles of various neurotransmitters in mediating the action of urocortin on the consolidation of memory, the animals were pretreated with different receptor antagonists. Urocortin facilitated the acquisition, consolidation and also retrieval of the passive avoidance response. The following receptor antagonists blocked the action of urocortin on consolidation: haloperidol, atropine, phenoxybenzamine, bicuculline, the CRF antagonist CRF9-41 and methysergide. Propranolol attenuated, but did not fully block the action of urocortin, while naloxone and nitro-L-arginine were ineffective. The results obtained demonstrate that urocortin is able to improve learning and memory and also retrieval processes in a passive avoidance learning in mice. D2, muscarinic cholinergic, alfa-adrenergic, CRF, serotonergic (5HT 1-2), GABA B receptors are involved in the consolidation of the passive avoidance response.

The effects of intracerebroventricularly administered endomorphin-2 (EM2) on open-field activity and the hypothalamo-pituitary-adrenal (HPA) system were investigated. EM2 (0.25-1 microg) significantly increased both the locomotor and the rearing activity, resulting in a bell-shaped dose-response curve. EM2 also enhanced corticosterone release, with an even more profound downturn phase at higher concentrations. The corticotropin-releasing hormone (CRH) antagonist alpha-helical CRH9-41 completely abolished the EM2-evoked endocrine and behavioral responses. These findings reinforce the hypothesis that the endomorphins may play a significant role in the regulation of locomotion, rearing activity and the HPA system through the release of CRH.

The present work was to study if the alpha-melanocyte-stimulating hormone (alpha-MSH) was involved in activation of the pituitary-adrenal axis (PAA) in rats. The hormone increased plasma corticosterone (CORT) level, and induced an anxiogenic response as indicated by results from the elevated plus-maze test. Intracerebroventricular administration of corticotropin-releasing factor (CRF) antiserum (1:10, 1:20 and 1:100 dilutions in 1microl volume), overcame both the anxiogenic response and the PAA activating effect induced by alpha-MSH (50 microg s.c.) in a concentration-dependent manner. CRF antibody at the doses applied did not modify either the elevated plus-maze responses or CORT level by itself. Our results reveal that both the anxiogenic and the PAA activating effects of alpha-MSH are mediated by CRF.

Recent data from various laboratories suggest that the activation of endogenous corticotropin-releasing factor (CRF) may contribute to the behavioral and neuroendocrine effects of cocaine. In the present study, the time-dependent variations in CRF-like immunoreactivity (CRF-LI) in the hypothalamus and several extrahypothalamic brain regions were determined after acute cocaine administration to handled rats. The intraperitoneal injection of 7.5 mg/kg cocaine led to a significantly decreased CRF-LI level in the basal forebrain and to a significantly increased CRF-LI level in the amygdala 60 min after administration, while the CRF-LI content was decreased in the hypothalamus and in the hippocampus 180 min after cocaine treatment. These results suggest that the durations of the effects of cocaine on CRF-LI are in the brain region-specific, which might contribute to the mediation of the diverse behavioral and neuroendocrine effects of cocaine.

The central corticotropin-releasing factor (CRF)-ergic system plays a critical role in anxiety and other behavioral stress responses. It has been shown that atrial (ANP), brain (BNP) and C-type (CNP) natriuretic peptides exert anxiolytic-like effects in behavioral studies. Our previous findings demonstrated that various doses of centrally administered ANP selectively altered the CRF content in different brain areas. In the present study, CRF immunoreactivity was determined in hypothalamic and extrahypothalamic brain regions after central injection of BNP or CNP in rats. A high dose (400 ng) of BNP significantly increased the CRF-like immunoreactivity (CRF-LI) in the hypothalamus and amygdala, while only a tendency towards an increase was found in the hippocampus. In the hypothalamus, the CRF-LI decreased after a high dose (400 ng) of CNP. The CRF-LI increased in the basal forebrain after a low dose (100 ng) of CNP. These results suggest that CRF may be involved in the mediation of some neuroendocrine and behavioral responses to BNP and CNP.

We have shown that ANP has anxiolytic-like effects in behavioral studies. Since CRF is thought to be involved in emotional state of the brain, the present study was undertaken to follow the possible alterations in corticotropin-releasing factor-like immunoreactivity (CRF-LI) in different regions of the brain in rats following ANP treatment. CRF-LI immunoreactivity was determined in hypothalamic and extrahypothalamic brain areas after central injection of atrial natriuretic peptide 1-28 (ANP1-28) in rats. After various doses of ANP1-28 administration the CRF-LI significantly increased in the hypothalamus, the hippocampus and the frontal cortex. In the amygdala, ANP caused a marked but nonsignificant CRF-LI enhancement. In the basal forebrain, the CRF-LI decreased. These results suggest that ANP1-28 may moderate activation of the CRF-ergic system in the brain which could be related to the neuroendocrine and behavioral action.

In the present study, the possible role of cortocotropin-releasing hormone (CRF) in the action of calcitonin gene-related peptide (CGRP) on the pituitary-adrenal axis and open-field activity of rats was tested. CGRP administered into the lateral brain ventricle led to a dose-dependent increase in plasma corticosterone level, which could be blocked by pretreatment with CRF antiserum. CGRP injected into the lateral brain ventricle increased the grooming and rearing activity and decreased the locomotor activity in an open field. On pretreatment with CRF antiserum, the action of CGRP on grooming was blocked, while the action on locomotion and rearing activity was unchanged. The results suggest that the CGRP-induced action on pituitary-adrenal activation is mediated by CRF. The action of CGRP on grooming in an open field is related to the pituitary-adrenal activation, and either CRF or adrenocorticotropic hormone or both may be involved in mediating the action of CGRP. The action of CGRP on rearing and locomotion is not affected by CRF antiserum, indicating that the two behavioral actions are regulated by different mechanisms.

Anxiety is a key symptom of the cocaine withdrawal syndrome in human addicts, and it is considered to be one of the major factors in precipitating relapse to chronic cocaine abuse. Corticotropin-releasing factor (CRF) plays an important role in the pathophysiology of anxiety and depression, and it may also be involved in the acute behavioral and neuroendocrine actions of cocaine. The role of endogenous CRF in cocaine withdrawal-induced anxiety was investigated in the present study. Animals were subjected to chronic cocaine (20 mg/kg, intraperitoneally, once a day for 14 days) administration. Rats tested 30 min after the last cocaine injection did not show withdrawal anxiety on the elevated plus maze or any alterations in brain CRF levels. Withdrawal (48 h) from chronic cocaine administration produced an intense anxiety-like behavior characterized by decreased open arm exploration. Immunoreactive CRF (CRF-LI) levels were selectively altered in the hypothalamus, in the amygdala and in the basal forebrain structures at the time of the behavioral anxiety, reflecting an increased activity of brain CRF systems. Daily intracerebroventricular (i.c.v.) pretreatment with an immunoserum raised against CRF completely prevented the development of anxiety induced by cocaine withdrawal. These data suggest that extrahypothalamic-limbic CRF hypersecretion may be involved in the development of anxiety related to cocaine withdrawal and that the CRF system may be a useful target for new pharmacotherapies for cocaine withdrawal and relapse.

Although synthetic corticotropin-releasing hormone (CRH) is known to influence the secretion of the neurohypophysial hormones, the role of endogenous CRH in the rat brain is still unclear in this respect. Accordingly, experiments were scheduled to study the effects of intracerebroventricularly (i.c.v.) administered CRH-antiserum (AS) on the hyperosmosis-induced secretion of arginine-8-vasopressin (AVP), oxytocin (OXT) and corticosterone in Wistar male rats. A 2 microliters CRH-AS injection was given, and repeated 24 h later, 30 min prior to intraperitoneal administration of hypertonic saline (HS; 2.5% NaCl, 2 ml/100 g body weight) followed by decapitation in 15 min. Plasma AVP and OXT were measured by radioimmunoassay and corticosterone by fluorimetry. HS increased the levels of AVP, OXT and corticosterone. CRH-AS did not change the plasma concentrations of these hormones in 0.9% NaCl-treated animals. CRH-AS pretreatment prevented the corticosterone-releasing action of HS, and significantly moderated the HS-induced AVP and OXT increase. These findings suggest that the central CRH system may participate in the regulation of corticosterone and neurohypophysial hormone secretion evoked by acute osmotic challenge.

As corticotropin-releasing factor (CRF) and oxytocin (OXT) are released in response to various stressors and a role of CRF in stress-induced OXT secretion has been proposed by previous authors, the present experiments were scheduled to investigate the participation of the brain CRF system in the stress-evoked release of OXT, arginine-8-vasopressin (AVP) and corticosterone. CRF-antiserum (AS) was given into the lateral ventricle of the brain of Wistar male rats, and 24 h later, the injection was repeated 30 min prior to ether stress followed by decapitation in 5 min. Plasma OXT and AVP were measured by radioimmunoassay and corticosterone by fluorimetry. Ether stress increased the levels of corticosterone and OXT, but not that of AVP. CRF-AS alone did not change the secretion of these hormones. CRF-AS pretreatment blocked the corticosterone-releasing action of ether stress, whereas it exerted no influence on the stress-induced OXT secretion into the circulation. There was no effect of a combined application of CRF-AS and stress on the plasma AVP level. These results suggest that the central CRF system is involved in the ether stress-elicited corticosterone response, however CRF is unlikely to be connected with the regulation of OXT secretion under these experimental conditions.

Corticotropin-releasing factor (CRF) may mediate some of the neuroendocrine and behavioral responses to cocaine. In this study, the distribution of CRF-like immunoreactivity (CRF-LI) was determined in the hypothalamus and in several extrahypothalamic brain regions after acute cocaine administration in handled rats. CRF-LI decreased dose-dependently with cocaine administration in the hypothalamus and in the basal-forebrain structures. A small dose of cocaine (7.5 mg/kg) decreased CRF-LI in the hippocampus and in the frontal cortex. A significant, selective, dose-dependent increase in CRF-LI was found in the amygdala after cocaine injection. None of the investigated doses of cocaine altered CRF-LI in the striatum. These results suggest that acute cocaine administration alters brain CRF systems to contribute behavioral and neuroendocrine responses to cocaine.

The possible involvement of endogenous corticotropin-releasing factor (CRF) in the anxiogenic and pituitary-adrenal-axis-activating effects of cholecystokinin octapeptide sulfate ester (CCK 8) was investigated in rats. Intracerebroventricularly (i.c.v.) administered CCK 8 induced an anxiogenic response in an elevated plus-maze test, and enhanced the plasma corticosterone level. Pretreatment with different dilutions (1:10, 1:20 and 1:100, i.c.v.) of CRF antiserum and different doses of a CRF receptor antagonist, alpha-helical CRF (ahCRF, 0.001-1.0 microgram, i.c.v.) prevented the anxiogenic response to CCK 8 in a dose-dependent manner. None of the doses of CRF antiserum or ahCRF alone produced any alteration in either the elevated plus-maze paradigm or corticosterone level in saline-treated control rats. The results strongly suggest that the anxiogenic and hypothalamo-pituitary-adrenal-activating effects of CCK 8 are mediated via CRF.

The role of endogenous corticotropin-releasing factor (CRF) in the cocaine-induced corticosterone response was investigated by using the immunoneutralization and receptor blockade of endogenous CRF. Pretreatment with different dilutions (1:5, 1:10 and 1:20, i.c.v.) of CRF antibody and different doses of an antagonist for CRF receptors, alpha-helical CRF9-41 (alpha h-CRF, 0.001-1.0 micrograms, i.c.v.), dose-dependently prevented the cocaine-induced increase in corticosterone level. These results support the hypothesis that the activation of the hypothalamo-pituitary-adrenal (HPA) axis by cocaine is mediated through the release of endogenous CRF.

The effects of intracerebroventricular administration of synthetic ovine corticotropin-releasing factor (CRF 1-41) have been investigated on the retention of passive avoidance behaviour, and on the dopamine, norepinephrine and serotonin contents of the hypothalamus, mesencephalon, amygdala, septum and striatum, as well as on the plasma corticosterone levels of hypophysectomized and sham-operated rats. Treatment with CRF 1-41 20 min before the first retention test, 24 hours after the learning trial, significantly facilitated the passive avoidance behaviour of hypophysectomized animals in a dose-dependent manner. No effect was found in sham-operated rats. No significant effects of a wide dose range of intracerebroventricularly injected CRF on the monoamine contents of limbic brain structures were detected. However, the same doses of CRF 1-41 increased the plasma corticosterone level in sham-operated rats. The data suggest that the release of CRF from neurons in the limbic system does not alter the monoamine contents in this system, although this peptide facilitates the retention of the passive avoidance behaviour of hypophysectomized rats.