Foldes A, Maxwell C A, Rintoul A J, Edols R W
Neuroendocrinology. 1984 Mar;38(3):206-11. doi: 10.1159/000123892.
To clarify the role and site of action of gamma-aminobutyric acid (GABA) in ovine pineal glands, we have investigated the effects of aminooxyacetic acid (AOAA), an inhibitor of GABA transaminase, on endogenous GABA content and beta-adrenoceptor mediated pineal function in Merino sheep. A significant elevation of endogenous GABA levels was noted in the glands, but no effect was observed on radioligand binding in vitro to pineal beta-adrenoceptors following in vivo administration of AOAA. Incubation of washed pineal membranes with GABA or AOAA had no effect on ligand binding to beta-adrenoceptors. Incubation of Merino pineal slices with GABA inhibited isoprenaline-stimulated but not basal serotonin N-acetyltransferase (NAT) activity. Incubation of whole pineal homogenates with GABA was without effect on either isoprenaline-stimulated or basal adenyl cyclase activity. Thus, Merino pineal glands resemble bovine pineals in that beta-adrenoceptor mediated melatonin biosynthesis in both species may be regulated in part by GABA. Our results indicate that GABA may exert its effect on Merino pineal NAT activity at a locus distal to the site of action of adenyl cyclase; however, the detailed mechanism and physiological role of this regulation remain to be elucidated.
为阐明γ-氨基丁酸（GABA）在绵羊松果体中的作用及作用位点，我们研究了γ-氨基丁酸转氨酶抑制剂氨氧基乙酸（AOAA）对美利奴绵羊内源性GABA含量及β-肾上腺素能受体介导的松果体功能的影响。结果发现，腺体中内源性GABA水平显著升高，但体内给予AOAA后，体外放射性配体与松果体β-肾上腺素能受体的结合未受影响。用GABA或AOAA孵育洗涤后的松果体膜，对配体与β-肾上腺素能受体的结合也无影响。用GABA孵育美利奴松果体切片，可抑制异丙肾上腺素刺激的5-羟色胺N-乙酰转移酶（NAT）活性，但对基础NAT活性无影响。用GABA孵育整个松果体匀浆，对异丙肾上腺素刺激的或基础的腺苷酸环化酶活性均无影响。因此，美利奴松果体与牛松果体相似，两种动物中β-肾上腺素能受体介导的褪黑素生物合成可能部分受GABA调节。我们的结果表明，GABA可能在腺苷酸环化酶作用位点的远端对美利奴松果体NAT活性发挥作用；然而，这种调节的详细机制和生理作用仍有待阐明。
