Sweep C G, Boersma C J, Wiegant V M
Department of Pharmacology, Medical Faculty, State University of Utrecht, The Netherlands.
Neuropharmacology. 1990 Jan;29(1):61-8. doi: 10.1016/0028-3908(90)90084-5.
beta-Endorphin is the putative precursor molecule of gamma- and alpha-endorphin. To investigate whether long-term changes in the activity of cells producing beta-endorphin are paralleled by alterations in the enzymatic processing of beta-endorphin, the effects of chronic treatment of rats with dopamine (DA) receptor ligands were examined on the content of immunoreactivity of beta-, gamma- and alpha-endorphin of dissected regions of the pituitary gland and the brain. Treatment with the DA receptor antagonist, haloperidol, resulted in a significant increase in the concentration of immunoreactivity for beta-, gamma-, and alpha-endorphin in the neurointermediate lobe, and of beta-endorphin in the anterior lobe of the pituitary gland. Levels of immunoreactivity of alpha-melanotropin and beta-endorphin in plasma were elevated, but those of corticosterone were decreased. This indicates that, in the intermediate lobe, both the biosynthetic and the secretory activity of cells producing beta-endorphin had increased, whereas in the anterior lobe, the secretory activity of beta-endorphin cells had decreased. No effects were observed on the ratios beta-endorphin/gamma-endorphin and beta-endorphin/alpha-endorphin in the intermediate lobe. In the anterior lobe however, the ratio beta-endorphin/alpha-endorphin had significantly increased. The effects of chronic treatment with the DA receptor agonist, bromocriptine, on levels of hormones in pituitary and plasma were opposite to those induced by haloperidol. In the brain, treatment with haloperidol selectively increased the content of immunoreactivity for beta-, gamma- and alpha-endorphin of the hypothalamus and the hippocampus and did not affect levels of peptides in the other regions of the brain studied.(ABSTRACT TRUNCATED AT 250 WORDS)
β-内啡肽被认为是γ-内啡肽和α-内啡肽的前体分子。为了研究产生β-内啡肽的细胞活性的长期变化是否与β-内啡肽的酶促加工改变平行，研究了用多巴胺（DA）受体配体长期处理大鼠对垂体和脑的解剖区域中β-、γ-和α-内啡肽免疫反应性含量的影响。用DA受体拮抗剂氟哌啶醇处理导致神经中间叶中β-、γ-和α-内啡肽以及垂体前叶中β-内啡肽的免疫反应性浓度显著增加。血浆中α-促黑素和β-内啡肽的免疫反应性水平升高，但皮质酮的水平降低。这表明，在中间叶，产生β-内啡肽的细胞的生物合成和分泌活性均增加，而在垂体前叶，β-内啡肽细胞的分泌活性降低。在中间叶未观察到对β-内啡肽/γ-内啡肽和β-内啡肽/α-内啡肽比例的影响。然而，在垂体前叶，β-内啡肽/α-内啡肽的比例显著增加。用DA受体激动剂溴隐亭长期处理对垂体和血浆中激素水平的影响与氟哌啶醇诱导的影响相反。在脑中，用氟哌啶醇处理选择性地增加了下丘脑和海马体中β-、γ-和α-内啡肽的免疫反应性含量，并且不影响所研究的脑的其他区域中的肽水平。（摘要截断于250字）
