||Witkop, B. & Brossi, A. (1984). Natural toxins and drug development. In Natural Products and Drug Development (ed. P. Krogsgaard-Larsen, S. Brogger Christensen and H. Kofod), Alfred Benzon Symposium 20, pp. 283-300. Munksgaard, Copenhagen.
||P.370 bottom paragraph to p.371 top paragraph: "Investigations of amphibian skin gland secretions have been undertaken for a variety of reasons. They have been a source of material for biophysical research, for biochemical taxonomy to assess the systematic status of selected species groupings and their evolutionary relationships, and for the search for new pharmaceuticals (Cei, Erspamer & Roseghini, 1972 Witkop & Gossinger, 1983 primary source, Erspamer, 1994). Bernard Witkop, in particular, has worked extensively on the alkaloid fractions of granular gland secretions. He drew attention to the fact that dendrobatid (poison dart) frog alkaloids (batrachotoxins, histrionicotoxins and pumiliotoxins) have novel chemical structures and have proved to be a particularly useful tool in research into cell receptor sites and ion transport channels in cell membranes. These compounds have wide applications in biophysics, neurophysiology, pharmacology and synthetic organic chemistry (primary source). These authors have also noted the analgesic action of some components of the secretions. Dermorphin, a novel opioid heptapeptide produced in the skin of the South American leaf frogs, genus Phyllomedusa, has a 1000-fold greater effect than morphine at the same dosage level (primary source). While such analgesics may function as part of a defence strategy against a potential predator, inducing a soporific effect, it is possible that they also function as a pain relief mechanism to enable the amphibian to cope with predator-induced or other injury."