1,721,036 research outputs found
Facilitation of [3H]acetylcholine and [3H]5-hydroxytryptamine release from rat cerebral cortex synaptosomes by a factor extracted from the skin of the Australian frog Pseudophryne coriacea
No full textParallel bioassay of bombesin and litorin, a bombesin like peptide from the skin of Litoria aurea
No full textThe spectrum of biological activity exhibited by litorin, a bombesin‐like nonapeptide found in extracts of the skin of the Australian leptodactylid frog Litoria aurea was compared with that exhibited by the tetradecapeptide bombesin. Litorin proved to be more potent than bombesin on isolated smooth muscle preparations and on the urinary bladder in situ. However, it was less potent on dog systemic blood pressure and kidney vasculature, activation of the renin‐angiotensin system being slight or lacking. Gastrin release and acid secretion produced by litorin was more rapid in onset but less intense and less sustained than that elicited by bombesin. The same could be observed for pancreatic secretion. Gall bladder contraction stimulated by litorin was probably caused by a double action of the peptide, directly on the bladder smooth muscle, and indirectly by cholecystokinin release. In its effects on the myo‐electric activity of the dog duodenum (inhibition of spikes and increase in frequency of pacesetter potentials leading to the appearance of a sequence of slow and small potentials) litorin possessed approximately 50 to 70% of the activity of bombesin. 1975 British Pharmacological Societ
Dermorphin-related peptides from the skin of Phyllomedusa bicolor and their amidated analogs activate two mu opioid receptor subtypes that modulate antinociception and catalepsy in the rat.
No full textThree naturally occurring dermorphin-like peptides from the skin of the frog Phyllomedusa bicolor, the related carboxyl-terminal amides, and some substituted analogs were synthesized, their binding profiles to opioid receptors were determined, and their biological activities were studied in isolated organ preparations and intact animals. The opioid binding profile revealed a very high selectivity of these peptides for mu-sites and suggested the existence of two receptor subtypes, of high and low affinity. The peptides tested acted as potent mu-opioid agonists on isolated organ preparations. They were several times more active in inhibiting electrically evoked contractions in guinea pig ileum than in mouse vas deferens. When injected into the lateral brain ventricle or peritoneum of rats, the high-affinity-site-preferring ligand, [Lys7-NH2]dermorphin, behaved as a potent analgesic agent. By contrast, the low-affinity-site-preferring ligand, [Trp4,Asn7-NH2]dermorphin, produced a weak antinociception but an intense catalepsy
Parallel bioassay of 39 tachykinins on 11 smooth muscle preparations. Structure and receptor selectivity/affinity relationship
No full textParallel bioassay on smooth muscle preparations demonstrated that: all TKs having a neutral or basic residue at position 7 from the
C-terminus show a clear-cut preference for the NK1 TK receptor, reinforced by the presence of the aromatic doublet Phe-Phe or Phe-Tyr
(aromatic TKs); all aliphatic TKs (Phe-Ile/Val) having an acidic residue at position 7 show a clear-cut preference for NK2/NK3 receptors,
generally without selectivity for a single receptor. However, in aromatic TKs having the same acidic residue, the preference for NK2/NK3
receptors is weakened, with a more or less pronounced co-preference for the NK1 receptor. Amino acid substitutions in the C-terminal
tripeptide may influence receptor affinity
Pharmacological studies of 'sapo' from the frog Phyllomedusa bicolor skin: a drug used by the Peruvian Matses Indians in shamanic hunting practices.
No full textThe dried skin secretion from Phyllomedusa bicolor, 'sapo', is used by the Matses Indians of the Northern Peru, in shamanic rites mainly designed to improve luck in hunting. When rubbed into burned, exposed areas of the skin, the drug causes the prompt appearance of violent peripheral gastrointestinal and cardiovascular effects soon followed by remarkable central effects (increase in physical strength, heightening of senses, resistance to hunger and thirst, exalted capacity to face stress situations). All the peripheral and most of the central effects of 'sapo' can be ascribed to the exceptionally high content of the drug (up to 7% of its weight) in potently active peptides, easily absorbed through the burned, inflamed areas of the skin. The concentration in 'sapo' of the single peptides (phyllocaerulein, phyllomedusin, phyllokinin, demorphins and deltorphins) has been determined by bioassay, and peptide contents were correlated with the different symptoms of the 'sapo' intoxication
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