Unité de Physiologie de la Reproduction et des Comportements (PRC), INRAE, CNRS, IFCE, Université de Tours, Nouzilly, France.
Département Productions Animales, Agroalimentaire, Nutrition (P3AN), Agrocampus Ouest, Rennes, France.
Front Endocrinol (Lausanne). 2021 Feb 8;11:612651. doi: 10.3389/fendo.2020.612651. eCollection 2020.
The neuropeptide oxytocin (OT) promotes maternal care and social affiliation in adults but its importance in infant attachment still remains unknown. True animal models of infant attachment are extremely rare, and the sheep (in complement to non-human primates) is one of the few that provides the opportunity to investigate its neuroendocrinological basis. In the lamb, access to the udder has strong rewarding properties for the establishment of a preferential relationship with the mother. Therefore, the present study explored the possible involvement of OT through its release during close social contacts with the mother. The first experiment revealed that lambs having free access to the udder from birth onward developed, by 12 h of age, a clear preference for their mothers over another maternal ewe. Delaying access to the udder for six, four or even only 2 h starting at birth, by covering the ewe's udder, resulted in the lack of such a preference without affecting general activity. These effects persisted in most cases at 24 h but by 72 h of age a bond with the mother was clearly expressed. Experiment two showed that social interactions with the mother were followed by a release of OT in the plasma when lambs had the possibility to suckle. Non-nutritive interactions were without effects. Preliminary data on two subjects suggested that OT might also increase in the cerebrospinal fluid after suckling. Finally, in the third experiment, oral administration of a non-peptide OT receptor antagonist (L-368-899, Merck) over the first 4 h after birth led to decreased exploration of the mother's body compared to lambs receiving saline, and impaired the expression of a preference for the mother at 24 h. The effects were no longer observed at 48 h. Our findings demonstrate that both delayed access to the mother's udder and OT receptor antagonist alter the onset of mother preference in newborn lambs. This suggests that central OT facilitates the development of filial attachment through its release during suckling.
神经肽催产素（OT）促进成人的母婴护理和社交联系，但它在婴儿依恋中的重要性仍不清楚。真正的婴儿依恋动物模型极为罕见，而绵羊（与非人类灵长类动物互补）是少数有机会研究其神经内分泌基础的动物之一。在羔羊中，接触乳房对建立与母亲的优先关系具有强烈的奖励作用。因此，本研究通过在与母亲进行密切的社会接触时释放 OT 来探索其可能的参与。第一项实验表明，从出生开始就可以自由接触乳房的羔羊，在 12 小时龄时，对其母亲表现出明显的偏好，而不是对另一只母羊表现出偏好。从出生开始，通过覆盖母羊的乳房，将接触乳房的时间延迟 6、4 甚至 2 小时，会导致这种偏好的缺失，而不会影响一般活动。在大多数情况下，这些影响持续到 24 小时，但到 72 小时龄时，与母亲的联系明显表达出来。实验二表明，当羔羊有吸吮的可能性时，与母亲的社会互动会导致血浆中 OT 的释放。非营养性互动没有影响。对两名受试者的初步数据表明，吸吮后 OT 也可能在脑脊液中增加。最后，在第三个实验中，在出生后的前 4 小时内，给羔羊口服非肽 OT 受体拮抗剂（L-368-899，默克），与接受生理盐水的羔羊相比，会导致对母亲身体的探索减少，并在 24 小时时损害对母亲的偏好表达。48 小时后不再观察到这些影响。我们的发现表明，延迟接触母亲的乳房和 OT 受体拮抗剂都会改变新生羔羊对母亲偏好的出现。这表明中枢 OT 通过在吸吮期间释放来促进亲子依恋的发展。
