Mena F, Aguayo D, Pacheco P, Morales M T
Departamento de Fisiología, Universidad Nacional Autónoma de México, D.F.
Neuroendocrinology. 1995 Jun;61(6):722-30. doi: 10.1159/000126900.
We injected, i.e., intracerebroventricularly (ICV) or systematically, small amounts of adrenaline (ADR), noradrenaline (NA), isoproterenol (ISOP) and dopamine (DA) in urethane-anesthetized lactating rats, and determined the effects on isometrically recorded intramammary pressure (IMP) responses to exogenous oxytocin (OXY). While centrally administered ADR, NA and DA provoked increased IMP responses to OXY, the beta-adrenergic agonist ISOP induced the opposite effect. These effects were reversible, dose related and also occurred in hypophysectomized rats. However, when injected systematically, all adrenergic agonists but DA depressed IMP responses to OXY. Further experiments showed that central effects of catecholamines were exerted by regulating ductal tone, through the direct innervation of the mammary glands. Thus, whereas complete blockage of these effects occurred after selective denervation of the mammary glands, increased ductal tone resulted from ICV administration of ISOP. Finally, evidence was also obtained that antagonistic alpha- and beta-adrenergic mechanisms may interact with each other to regulate milk ejection, and with afferent signals from the mammary glands. Thus, beta-adrenergic inhibition upon IMP was counteracted by either NA administration or by activation of ductal mechanoreceptors. Together, these results suggest that regulation of milk ejection may involve neurally mediated influences on mammary contractility. Such actions would interact closely with afferents from the mammary gland influencing ductal tone.
我们向经乌拉坦麻醉的泌乳大鼠脑室内（ICV）或全身注射少量肾上腺素（ADR）、去甲肾上腺素（NA）、异丙肾上腺素（ISOP）和多巴胺（DA），并测定其对记录到的乳腺等长压力（IMP）对外源性催产素（OXY）反应的影响。虽然中枢给予ADR、NA和DA会引起IMP对OXY的反应增强，但β-肾上腺素能激动剂ISOP却产生相反的效果。这些作用是可逆的、与剂量相关的，并且在垂体切除的大鼠中也会出现。然而，当全身注射时，除DA外的所有肾上腺素能激动剂都会抑制IMP对OXY的反应。进一步的实验表明，儿茶酚胺的中枢作用是通过调节导管张力，经由对乳腺的直接神经支配来发挥的。因此，在对乳腺进行选择性去神经支配后，这些作用完全被阻断，而ICV给予ISOP则会导致导管张力增加。最后，还获得了证据表明，α-和β-肾上腺素能拮抗机制可能相互作用以调节乳汁排出，并与来自乳腺的传入信号相互作用。因此，NA给药或导管机械感受器的激活可抵消β-肾上腺素能对IMP的抑制作用。总之，这些结果表明，乳汁排出的调节可能涉及神经介导的对乳腺收缩性的影响。这种作用将与来自乳腺影响导管张力的传入神经密切相互作用。
