Palego L, Giromella A, Marazziti D, Borsini F, Naccarato A G, Giannaccini G, Lucacchini A, Cassano G B, Mazzoni M R
Department of 'Psichiatria, Neurobiologia, Farmacologia e Biotecnologie', University of Pisa, via Bonanno 6, I-56100, Pisa, Italy.
Brain Res. 1999 Jan 16;816(1):165-74. doi: 10.1016/s0006-8993(98)01156-1.
The reproducibility of serotonin (5-HT) and (+)8-OH-DPAT-mediated inhibition of adenylyl cyclase activity was assessed in membranes, stimulated by forskolin, of rat frontal cortex postmortem as well as of human fronto-cortical, hippocampal and dorsal raphe tissues obtained from autopsy brains. The results revealed that differences between basal and forskolin-stimulated enzyme activities were still significant after 48 h postmortem in rat cortex and in all human brain regions up to 46 h after death. However, a decrease of about 17 and 26% in forskolin-stimulated adenylyl cyclase activity was observed at 24 and 48 h, respectively, in rat cortex. 5-HT and the 5-HT1A receptor agonist, (+)8-hydroxy-2(di-N-propylamino)tetraline (8-OH-DPAT), were able to inhibit forskolin-stimulated adenylyl cyclase activity in a dose-dependent manner for 48 h after death in rat and human brain. In rat cortex, both 5-HT and (+)8-OH-DPAT potencies (EC50, nM) and efficacies (percent of maximum inhibition capacity, %) varied significantly with postmortem delay. Conversely, in human tissues, postmortem delay and subject age did not modify agonist potencies and efficacies. Furthermore, a regionality of 5-HT potency and efficacy was revealed in the human brain. 5-HT was equally potent in cortex and raphe nuclei, while being more potent but less effective in hippocampus. (+)8-OH-DPAT was more active in hippocampus and raphe nuclei than in cortex. (+)8-OH-DPAT behaved as an agonist in all areas, as its efficacy was similar or greater than those obtained with 5-HT. The (+)8-OH-DPAT dose-response curve was completely reversed by 5-HT1A receptor antagonists in rat cortex and all human brain areas. In conclusion, we suggest here that differences between rat and human brain might exist at the level of postmortem degradation of 5-HT-sensitive adenylyl cyclase activity. In human brain, 5-HT1A receptor-mediated inhibition of adenylyl cyclase seems to be reproducible, suggesting that reliable experiments can be carried out on postmortem specimens from patients with neuropsychiatric disorders.
在大鼠额叶皮质死后的膜以及从尸检大脑获得的人类额叶皮质、海马体和中缝背核组织中，评估了血清素（5-羟色胺，5-HT）和（+）8-羟基-二丙基氨基四氢萘（8-OH-DPAT）介导的腺苷酸环化酶活性抑制的可重复性。结果显示，在大鼠皮质死后48小时以及人类所有脑区死后46小时内，基础酶活性与福斯高林刺激后的酶活性之间的差异仍然显著。然而，在大鼠皮质中，分别在死后24小时和48小时观察到福斯高林刺激的腺苷酸环化酶活性下降了约17%和26%。5-HT和5-HT1A受体激动剂（+）8-羟基-2（二丙基氨基）四氢萘（8-OH-DPAT）能够在大鼠和人类大脑死后48小时内以剂量依赖的方式抑制福斯高林刺激的腺苷酸环化酶活性。在大鼠皮质中，5-HT和（+）8-OH-DPAT的效能（半数有效浓度，EC50，纳摩尔）和效力（最大抑制能力百分比，%）均随死后延迟时间而显著变化。相反，在人类组织中，死后延迟时间和受试者年龄并未改变激动剂的效能和效力。此外，在人类大脑中还揭示了5-HT效能和效力的区域差异。5-HT在皮质和中缝核中的效能相同，而在海马体中效能更高但效力更低。（+）8-OH-DPAT在海马体和中缝核中的活性高于皮质。（+）8-OH-DPAT在所有区域均表现为激动剂，因为其效力与5-HT相似或更高。在大鼠皮质和所有人类脑区中，5-HT1A受体拮抗剂可完全逆转（+）8-OH-DPAT的剂量-反应曲线。总之，我们在此表明，大鼠和人类大脑在5-HT敏感的腺苷酸环化酶活性的死后降解水平上可能存在差异。在人类大脑中，5-HT1A受体介导的腺苷酸环化酶抑制似乎具有可重复性，这表明可以对患有神经精神疾病患者的死后标本进行可靠的实验。
