Heynen A J, Sainsbury R S
Department of Psychology, University of Calgary, Alberta, Canada.
Brain Res Bull. 1991 Jan;26(1):29-36. doi: 10.1016/0361-9230(91)90188-p.
The purpose of the present study was to determine the role of norepinephrine in the generation of hippocampal theta activity. Experiments were performed on urethane-anesthetized rats, implanted with recording electrodes in the dentate gyrus and stimulating electrodes in the dorso-medial posterior hypothalamus. The effects of norepinephrine on hippocampal theta activity was studied by directly infusing norepinephrine and other noradrenergic agents into the hippocampus. Norepinephrine microinfusion produced a decrease in the amplitude of theta activity as observed in the polygraph chart record. Subsequent spectral analyses demonstrated a decrease in power at peak theta frequencies, as well as a decrease in power at frequencies between 20-25 Hz (noise). The inhibitory effect of norepinephrine on hippocampal type 2 theta activity was found to be mediated by alpha 2-adrenergic receptors. Microinfusions of an alpha 2 agonist (detomidine) mimicked the effects produced by norepinephrine, whereas alpha 1 and beta agonists were ineffective. The inhibitory effect of detomidine was blocked by microinfusions of an alpha 2 antagonist (tolazoline), which indicates that the site of action was specific to the noradrenergic alpha 2 receptor.
本研究的目的是确定去甲肾上腺素在海马θ活动产生中的作用。实验在乌拉坦麻醉的大鼠身上进行，在齿状回植入记录电极，在背内侧下丘脑后部植入刺激电极。通过将去甲肾上腺素和其他去甲肾上腺素能药物直接注入海马，研究了去甲肾上腺素对海马θ活动的影响。去甲肾上腺素微量注射导致θ活动幅度降低，这在测谎仪图表记录中可以观察到。随后的频谱分析表明，θ峰值频率处的功率降低，以及20 - 25Hz频率（噪声）处的功率降低。发现去甲肾上腺素对海马2型θ活动的抑制作用是由α2 - 肾上腺素能受体介导的。α2激动剂（右美托咪定）的微量注射模拟了去甲肾上腺素产生的效果，而α1和β激动剂则无效。右美托咪定的抑制作用被α2拮抗剂（妥拉唑啉）的微量注射所阻断，这表明作用部位对去甲肾上腺素能α2受体具有特异性。
