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withdrawn for each injection.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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