K 41498

Urocortins (Ucn) 1, 2 and 3, human homologues of fish urotensin I, form the corticotropin-releasing factor (CRF) family, together with CRF, urotensin I and sauvagine. Ucn 3 is a novel member of this family and is a specific ligand for CRF type 2 receptor. CRF type 2 receptor is thought to mediate the stress-coping responses, such as anxiolysis, anorexia, vasodilatation, a positive inotropic action on myocardium and dearousal. Endogenous ligands for the CRF type 2 receptor expressed in the cardiovascular tissues, such as the myocardium, have long been unknown. We have shown expression of Ucn 3 as well as Ucn 1 in the human heart. Ucn 3 is also expressed in the kidney, particularly distal tubules. Studies in various rat tissues showed that high concentrations of immunoreactive Ucn 3 were found in the pituitary gland, adrenal gland, gastrointestinal tract, ovary and spleen in addition to the brain, heart and kidney. These observations suggest that Ucn 3 is expressed in various tissues including heart and kidney, and may regulate the circulation in certain aspects of stress and diseases, such as inflammation. Ucn 1 and 3 appear to have important pathophysiological roles in some cardiovascular diseases.

Corticotropin-releasing factor (CRF), urocortin, sauvagine and urotensin I form the CRF family. These peptides bind with different affinities to two subtypes of CRF receptor (CRFR), CRFR1 and CRFR2. The latter exists as two splice variants, the neuronal CRFR2a and the peripheral CRFR2b. CRFR is a G protein-dependent receptor which acts mainly through Gs enhancing cAMP production. However, CRFR1 expressed in neutrophils of the spleen in response to immunologic stimulation and psychological stress does not seem to function through Gs, as indicated by the inability of CRF to stimulate the cAMP production of CRFR1+ neutrophils. Besides the two receptors, a 37 kD CRF binding protein (CRF-BP) binds several CRF peptides with high affinity. CRFR and CRF-BP do not share a common amino acid sequence representing the ligand binding site. In view of the unusually slow offrate of CRF-BP, it is proposed that CRF-BP provides an efficient uptake of free extracellular CRF. Thus, the time of exposure of CRFR to CRF or urocortin can be limited. At this time, the fate of the ligand CRF-BP complex is unclear. CRFR1 is not only involved in the hypophyseal stimulation of corticotropin release, but hippocampal CRFR1 mediates enhancement of stress-induced learning. CRFR1 may also be involved in basic anxiety. In contrast, at least in the mouse, CRFR2 of the lateral intermediate septum mediates tonic impairment of learning. In response to stressful stimuli or after local injection of high CRF doses, CRFR2 mediates anxiety. Effects requiring CRFR2 can be blocked specifically by the recently developed peptidic antagonist antisauvagine-30.

The secretions of the Giant Monkey FrogPhyllomedusa bicolorare used by populations in the Amazon regions (mainly the indigenous Katukinas and Kaxinawás). The so-called "toad vaccine" or "kambô" is applied as a medication for infections and to prevent diseases, and also as physical and mental invigorator, and analgesic. Since the 1980s, researchers and companies have been interested in the composition of these secretions. Phyllomedusin, phyllokinin, caerulein and sauvagine are the polypeptides in these secretions that can cause intense effects on smooth muscles, vessels provoking, nausea and vomiting, arterial hypotension, flushing, palpitations, nausea, vomiting, bile secretion and angioedema. These actions are similar to bradykinin. However, the feeling of well-being and improvement of motor skills described by the users seems to be associated with dermorphine, caerulein or deltorphin - peptides with analgesic properties - and their affinity for the opiate receptor systems. Caerulein is a peptide that increases digestive secretions. Phyllomedusin and Phyllokinin lead to blood pressure and digestive effects. Sauvagine release corticotropin and mimics the physiological reactions of exposure to stress. Deltorphins and dermorphins have high affinity for the opiate receptor system and can lead to analgesia. The fame acquired by the therapy motivated the use by individuals from urban areas worldwide, without safety considerations. While in indigenous communities, there is an entire cultural tradition that provides relative safety to the application, however, the extension of use to individuals from urban areas worldwide is a problem, with reports of severe adverse effects and deaths. Undoubtedly, the skin secretions of thePhyllomedusagenus contain substances of intense pharmacological action and that can lead to research for therapeutic uses, but control over their application in rituals outside the forest is needed due the risks presented.