mise à jour du
19 février 2004
Biochemistry & Behavior
1987; 26; 277-279
Hypophysectomy prevents ACTH-induced
yawning and penile erection in rats
Serra G, Fratta W, Collu M, Gessa GL
Institute of pharmacology, University od Caligari, Italy

The administration of ACTH or ACTH-derived neuropeptides into the cerebrospinal fluid (CSF) in mammals induces a behavioural syndrome characterized by recurrent episodes of stretching, yawning and penile erection.

A similar behavioural syndrome, though less intense, may be induced by systemic administration of minute doses of apomorphine or other dopamine (DA) receptor agonists .

We have recently shown that inhibition of protein synthesis or hypophysectomy prevents apomorphine induced yawning and penile erection and suggested that these behavioural responses might be mediated by the release of ACTH or MSH newly synthetized from pituitary, reaching the brain via a retrograde portal flow. Further support for this hypothesis is provided by the finding that small doses of apomorphine stimulate ACTH release from pituitary.

However, an alternative explanation for the suppressant effect of hypophysectomy on yawning and penile erection may be that hypophysectomy modifies the sensitivity of receptors in the CNS to DA and/or ACTH responsible for such behaviours.

To clarify this hypothesis, we investigated whether hypophysectomy would modify yawning and penile erection induced by the administration of ACTH 1-24 in rats.

The present results indicate that hypophysectomy prevents ACTHI induced yawning and penile erection, suggesting that pituitary has a permissive role for the expression of specific behaviours mediated by ACTH and related neuropeptides. [...]


We found that the removal of pituitary, besides preventing apomorphine-induced yawning and penile erection, also antagonizes these behavioral responses induced by ACTH suggest that hypophysectomy modifies the sensitivity of receptors to DA and ACTH in the brain mediating yawning and penile erection.

The consequence of hypophysectomy seems to be selective for specific receptors since it causes the loss of apomorphine and ACTH ability in inducing yawning and penile erection, but fails to affect other behavioural responses to apomorphine, such as the hypomotifity produced by the minute doses of apomorphine, and motor stimulation and stereotypy produced by high doses of the drug (Serra et al., in preparation). Moreover, de Wied's group has shown that hypophysectomy docs not prevent the positive effect of ACTH and ACTH-derived peptides on memory and learning in rats, suggesting that the central ACTH receptors involved in such response are not modified by hypophysectomy.

Pituitary might control the sensitivity of central DA and ACTH receptors mediating yawning and penile erection directly, via some pituitary hormone, reaching the brain via retrograde portal flow, or indirectly, via some pituitarycontrolled hormone. Whereas testosterone might have a permissive role in the sexual effect of apomorphine and ACTH, the lack of testosterone cannot account for the loss of the yawning response since castration fails to modify such effect elicited by ACTH or apomorphine administration.

The present results are of great interest because they suggest that pituitary has a "trophic" action not only on peripheral target organs but also on structures in brain controfling specific behavioural responses.

These results leave unresolved.the problem of whether yawning and penile erection induced by apomorphine and other DA-agonists involve the release of ACTH-derived neuropeptides from the pituitary or from central peptidergic neurons. The solution of this problem is hampered by the fact that, unfortunately, no specific antagonists for central receptors to ACTH and ACTH-related peptides are presently available. However we have observed that sulpiride, a specific DA receptor blocker, potently antagonizes apomorphine-induced yawning but fails to affect this behavioural response induce by ACTH, suggesting that ACTH-induced yawning involves neither DA receptor activation nor DA release.

Serra G et al Hypophysectomy prevents ACTH-induced yawning and penile erection in rats Pharmacology Biochemistry & Behavior 1987; 26; 277-279
Serra G , Collu M and Gessa GL Yawning is elicited by D2 dopamine agonists but is blocked by D1 antagonist Psychopharmacology 1987; 91; 330-337
Serra G, Gessa GL Hypophysectomy prevents yawning and penile erection but not hypomotility induced by apomorphine Pharmacology Biochemistry & Behavior 1983; 19; 917-919
Serra G et al Cycloheximide prevents apomporphine induced yawning, penile erection and genital grooming in rats European Journal of Pharmacology1983; 86; 279-282