Daisley J N, Rose S P
Brain Research Group, Department of Biology, The Open University, Milton Keynes MK7 6AA, UK.
Brain Res. 1999 Nov 20;847(2):149-56. doi: 10.1016/s0006-8993(99)01986-1.
The present work describes interactions between adenosine and the amino acids glutamate and GABA in slices of intermediate medial hyperstriatum ventrale (IMHV), an area of the chick brain known to be involved in learning and memory events associated with a one-trial passive avoidance task. In slices derived from the IMHV of untrained chicks, the A(1) receptor agonist N(6)-cyclohexyladenosine (CHA; 10 microM) specifically inhibited glutamate release. Conversely, cyclopentyltheophylline (CPT; 100 microM an A(1) antagonist) increased glutamate release from the slices and blocked the CHA-induced inhibition of glutamate. The A(2) receptor agonist 2-p-(2-carboxylethyl)-phenylamino-5'-N-ethylcarboxamido adenosine hydrochloride (CGS 21680) selectively increased glutamate release when applied at 5 microM while it selectively inhibited GABA release at a lower concentration (10 nM). The addition of NMDA to the medium, resulted in increased adenosine release equivalent to that found following stimulation with 50 mM KCl. Both the NMDA and the KCl-induced increases were eliminated by addition of D-2-amino-5 phosphopentanoic acid (D-AP5), an NMDA-receptor antagonist. Slices prepared from the IMHV of chicks following successful training on the task showed enhanced adenosine release 30 min, 1, 3 and 6.5 h after training compared to chicks trained to peck a water-coated bead. The results show that changes in adenosine release from the IMHV accompany memory formation in the chick. We suggest that adenosine-amino acid transmitter interactions potentially via the activation of NMDA receptors, a necessary step in long-term memory formation for the task, may modulate the formation of memory for the one-trial passive avoidance task.
本研究描述了腺苷与氨基酸谷氨酸和γ-氨基丁酸（GABA）在鸡脑中间内侧腹侧超纹状体（IMHV）切片中的相互作用，该区域已知参与与单次被动回避任务相关的学习和记忆活动。在未经训练的雏鸡IMHV切片中，A(1)受体激动剂N(6)-环己基腺苷（CHA；10微摩尔）特异性抑制谷氨酸释放。相反，环戊基茶碱（CPT；100微摩尔，一种A(1)拮抗剂）增加了切片中谷氨酸的释放，并阻断了CHA诱导的谷氨酸抑制作用。A(2)受体激动剂2-对-(2-羧乙基)-苯氨基-5'-N-乙基羧酰胺腺苷盐酸盐（CGS 21680）在5微摩尔浓度下应用时选择性增加谷氨酸释放，而在较低浓度（10纳摩尔）时选择性抑制GABA释放。向培养基中添加N-甲基-D-天冬氨酸（NMDA）会导致腺苷释放增加，与用50毫摩尔氯化钾刺激后观察到的增加量相当。NMDA和氯化钾诱导的增加均被NMDA受体拮抗剂D-2-氨基-5-磷酸戊酸（D-AP5）消除。在任务训练成功后的雏鸡IMHV制备的切片显示，与训练啄食涂有水的珠子的雏鸡相比，训练后30分钟、1小时、3小时和6.5小时腺苷释放增强。结果表明，IMHV中腺苷释放的变化伴随着雏鸡记忆的形成。我们认为，腺苷-氨基酸递质相互作用可能通过NMDA受体的激活，这是该任务长期记忆形成的必要步骤，可能调节单次被动回避任务记忆的形成。
