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mise à jour du
1 décembre 2004
Experientia
1961;17:90
lexique
Stretching activity in dogs intracisternally injected with a synthetic melanocyte-stimulating hexapeptide
W. FERRARI, G. L. GESSA, and L. VARGIU
Istituto di Farmacologia, Università degli Studi
Cagliari (Italy), July 13, 1960
Department of neuroscience Cagliari University Italy
 
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In dogs, intracisternal injections of highly purified ACTH preparations induce typical, prolonged, and repeated stretching crises. Similar effects are caused by purified MSH preparations and by solutions of ACTH made with NaOH N/10 treated at 100°C for 20 min. These findings suggest that the chemical groups eliciting the stretching responses are related with those stimulating melanocytes. This correlation is supported by results obtained with dogs given intracisternally the acetate salt of the synthetic hexapeptide H Glu (NH2)-His-Phe-Arg-Try- Gly-OH with MSH-like activity. 750 ¶kg or less of this peptide (given intracisternally) evoke stretching responses similar to those following injections of MSH or ACTH. 1.5 mg/kg of the peptide causes lasting depression and scialorrhea but not a stretching crisis.

The melanocyte stimulating effect of the peptide is 2 x 10 5/g; that of a purified MSH preparation (732179 A by Armour Laboratories, Chicago) 5 x 108 U/g. The threshold dose for the stretching response was respectively 500 and 5 ¶/kg: indeed these two different pharmacological actions are strictly related. The hexapeptide, but not MSH, shows a paradoxycal behaviour and a pharmacological response evoked by the polypeptide may change qualitatively with respect to the dose given intracisternally.

The Figure illustrates a typical stretching crisis in a dog injected intracisternally with the hexapeptide.

stretchingacth