mise à jour du
28 novembre 2002
Stretchings and Yawnings induced by
Adrenocorticotrophic Hormone
GL Gessa, L Vargiu, W Ferrari
 Department of Pharmacology, University of Cagliari, Italy.
Tous les travaux de MR Melis & A Argiolas 
Tous les travaux de M Eguibar & G Holmgren


Natural crude or purified preparation of adrenocortîcotrophic hormone (ACTH) and melanotrophine(MSH) can induce stretching and yawing motions in various species of animals when injected intracisternally. This property is also shared by synthetic polypeptides endowed with MSH and/or ACTH activity.
Experiments were performed to establish whether or not synthetic beta(1-24) ACTH can induce stretching and yawing motions. This polypeptide has an ACTH potency of 106 i.u./mg.
The experiments were performed on unanaesthetized adult mongrel dogs, cats and vervet monkeys (Cercopithecus aethiops). The animals, which had been fasting for 12 h were injected intracisternally with various doses of the drug being tested. The drugs were dissolved in 0-5 ml of saline and 0-5 ml of liquor was withdrawn for each injection. The stretching potency of beta(1-24)ACTH was assessed in dogs by determining the minimal dose which produced the 'stretching crisis'. (It was considered that this had been reached when the dogs showed, at intervals net exceeding 30 mn, long periods of stretching each of which began immediately after the preceding one.)
The restults of experiments performed on dogs are shown in Table 1. They indicate that beta(1-24)ACTH is as potent as pure natural ACTH in producing stretching motions. The symptoms induced by beta(1-24)ACTH are the same as those indnced by the natural hormone: that is, after a delay of about 1- 2 h, the dogs start to stretch and yawn in the way they usually do when wakening from physiological sleep. The intervals between successive stretching acts become shorter and shorter until eventually the stretching crisis is reached.
Beta(1-24)ACTH induces in cats repeated, isolated stretchings in a similar fashion to the natural hormone, but with only a few yawns. These symptoms are accompanied by marked drowsiness.
In monkeys, beta(1-24)ACTH mostly induces repeated yawing. (It should be remembered, however, that yawing in monkeys may be an emotional behaviour.) The periods of stretching are very limited in number. Furthermore, the yawnings and stretchings are accompanied by an obvious drowsiness.
The stretching activity persists for about 24-72 h in dogs, and 6-12 h. in cats and monkeys; it ends with a complete return to normal beliaviour.
We do net know whether the phenomenon described here has any physiological meaning. At present, we are investigating the effect ofmicro-injections of ACTH in diferrent areas of the central nervous system.
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