The nociceptin/orphanin FQ receptor ligand acetyl-RYYRIK-amide exhibits antagonistic and agonistic properties.

The hexapeptide acetyl-RYYRIK-amide (Ac-RYYRIK-NH(2)) has recently been reported to act as partial agonist of the nociceptin/orphanin FQ (noc/OFQ) receptor expressed in CHO cells. In addition, this peptide acts as a competitive antagonist of noc/OFQ-stimulated GTPgamma(35)S binding in rat brain membranes as well as of the noc/OFQ-evoked chronotropic effect in rat cardiomyocytes. In contrast to this antagonism, in the present study, Ac-RYYRIK-NH(2) was found to behave as an agonist at noc/OFQ receptors, affecting spontaneous locomotor activity. When administered intracerebroventricularly (i.c.v.), noc/OFQ and Ac-RYYRIK-NH(2) inhibited spontaneous locomotor activity in mice with ID(50) of 1.1 and 0.07 nmol, respectively. Co-administration of both peptides lead to additive effects. The higher potency of Ac-RYYRIK-NH(2) could not be clearly explained by differential metabolism, because in vivo microdialysis in rat striatum and in vitro metabolic inactivation by rat and mouse brain membranes revealed extensive inactivation of both peptides. Similar to Ac-RYYRIK-NH(2), [Phe(1)psi(CH(2)-NH)Gly(2)]noc/OFQ(1-13)-NH(2) ([F/G]NC(1-13)NH(2)) inhibited the noc/OFQ-stimulated GTPgamma(35)S binding in rat brain membranes (Schild constant 3.83 nM) and mouse brain sections, although several reports have shown that this peptide exhibits agonist activity of noc/OFQ in the CNS. Changes in the optimum conditions of the in vitro assay for GTP binding increased low partial agonism of Ac-RYYRIK-NH(2) in GTP binding response. To explain the discrepancy between the in vitro antagonism of G protein coupling of the noc/OFQ receptor and in vivo agonism of Ac-RYYRIK-NH(2) and of [F/G]NC(1-13)NH(2), it is suggested that low partial agonism of receptor/G protein coupling in native systems may be sufficient to evoke full biologic responses. The extent of partial agonism for GTP binding and of coupling reserve may vary in different systems, thus explaining why [F/G]NC(1-13)NH(2) and Ac-RYYRIK-NH(2) were reported to exhibit antagonist, partial agonist, or even full agonist properties, depending on the system studied.

Altered amygdalar CRF release and increased anxiety-like behavior in Sardinian alcohol-preferring rats: a microdialysis and behavioral study.

BACKGROUND: Dysregulation of the stress-regulatory corticotropin-releasing factor (CRF) system in the central nucleus of the amygdala (CeA) may be a factor in genetically determined alcohol preference. METHODS: To test this hypothesis, basal and restraint stress-induced CRF efflux in the CeA was determined by microdialysis in Sardinian alcohol-preferring (sP) and nonpreferring (sNP) rats. In addition, differences in anxiety-like behavior between sP and sNP rats were evaluated by using the elevated plus maze and conditioned defensive burying tests. RESULTS: Basal dialysate CRF levels in the CeA were elevated in the alcohol-preferring line (sP, 281.2+/-83.96 pg/ml; sNP, 70.2+/-16.76 pg/ml; p < 0.05). In contrast, no differences in whole-tissue CRF content in the CeA were observed (sP, 1143+/-142 ng/mg protein; sNP, 1181+/-139 ng/mg protein). Restraint stress elevated CRF dialysate concentrations in both sP and sNP rats. Rats of the sP line exhibited more anxiety-like behavior than sNP rats in the elevated plus maze but not in the conditioned defensive burying test. CONCLUSIONS: The results suggest that ethanol-preferring sP rats show a dysregulation in basal CRF release within the CeA that may, in turn, heighten ethanol intake and increase susceptibility to anxiogenic stimuli in these animals.

In vivo CRF release in rat amygdala is increased during cocaine withdrawal in self-administering rats.

Previous studies have suggested a role for corticotropin-releasing factor (CRF) in the central nucleus of the amygdala (CeA) in the aversive and anxiogenic effects of withdrawal from opiates and ethanol. To test whether this role of CRF extends to cocaine withdrawal as well, the release of CRF in rat amygdala was monitored by intracranial microdialysis during a 12-hour session of intravenous cocaine self-administration and subsequent 12-hour cocaine withdrawal period. Cocaine self-administration tended to lower dialysate CRF concentrations to approximately 75% of CRF levels in controls. In contrast, subsequent cocaine withdrawal produced a profound increase in CRF release, which reached peak levels of approximately 400% of baseline between 11 and 12 hours post-cocaine. These results provide evidence that cocaine withdrawal activates CRF neurons in the amygdala, a site that has been implicated in emotional and anxiogenic effects of stress and drug withdrawal syndromes.

Corticotropin-releasing hormone (CRH) receptors in the mesenteric small arteries of rats resemble the (2)-subtype.

The potencies of the corticotropin-releasing hormone (CRH) agonistic peptides oCRH, h/rCRH, frog sauvagine, and carp urotensin I and of the antagonistic peptide alpha-helical CRH9-41 were compared in 3 different in vitro assays: (a) receptor binding to rat brain membranes; (b) release of ACTH/beta-endorphin from rat pituitary cells; and (c) relaxation of rat mesenteric small arteries. From their potency profiles, especially from the high potency of sauvagine relative to CRH in the relaxation assay, it is concluded that the receptors mediating the hypotensive action of systemic CRH in vascular smooth muscle are different from those in the pituitary and brain, and may be identical or very similar to the recently cloned new CRH receptor type 2.

Sensitization of cocaine-stimulated increase in extracellular levels of corticotropin-releasing factor from the rat amygdala after repeated administration as determined by intracranial microdialysis.

Using intracranial microdialysis, the effect of repeated cocaine (30 mg/kg i.p.) versus saline administration for 10 consecutive days upon basal and stimulated release of corticotropin-releasing factor (CRF) was examined in the central amygdaloid nucleus (CeA) of anesthetized rats. No significant differences in basal CRF levels between daily cocaine and saline treated groups were found. However, after cocaine challenge (10 mg/kg i.p.) the increase in CRF overflow was significantly greater in cocaine- as opposed to saline-pretreated rats (266 +/- 55.4% versus 149 +/- 8.5% of basal levels). Local administration of 4-aminopyridine produced a significant increase in CRF efflux (195 +/- 58.5%) in daily cocaine-treated rats with only a weak response in the control group (127 +/- 30.9%). These data demonstrate that repeated administration of cocaine enhances cocaine-induced release of CRF in the rat CeA. The sensitization of CRF release may play a significant role in psychostimulant-induced sensitization phenomena.

Comparison of hCRF and oCRF effects on cardiovascular responses after central, peripheral, and in vitro application.

Three assays have been used to show that the neuropeptides human corticotropin-releasing factor (hCRF) and the ovine analogue oCRF produced substantial dose-dependent cardiovascular responses. The assays included intracerebroventricular (ICV) and intravenous (IV) administration in conscious rats, and also in vitro experiments with resistance arteries. Central administration of the peptides (0.1-10 micrograms, ICV) caused an increase in blood pressure and heart rate, whereas peripheral administration (0.75-750 micrograms/kg, IV) produced a decrease in blood pressure and tachycardia. Isometric ring preparations of mesenteric resistance arteries (diameter 200 microns) relaxed in response to both peptides (1-100 nM). In all cases, the effects were more pronounced for hCRF compared to compared to oCRF. Furthermore, all effects were inhibited by the CRF analogue alpha-helical CRF(9-41), the effect of the analogue being most potent against oCRF. The results of all three assays indicate that the difference in structure between hCRF and oCRF produces differences in biological activity.

Hoarseness; a unique clinical presentation for renal cell carcinoma.

The first reported case of an isolated metastasis to the larynx from a regionally localized renal cell carcinoma presenting clinically as hoarseness is discussed. Aggressive management and outcome are presented.

Massive gastric hemorrhage from submucosal arterial malformation.

In a patient with massive gastric bleeding, the cause was found to be rupture of a submucosal arterial malformation. The bleeding site was identified endoscopically and the lesion was removed by local resection. This is the 28th case of this entity to be reported.