Kolta A, Reader T A
Département de physiologie, Faculté de médecine, Université de Montréal, Québec, Canada.
Can J Physiol Pharmacol. 1989 Jun;67(6):615-23. doi: 10.1139/y89-098.
The catecholamines noradrenaline and dopamine have been proposed as neuromodulators of cortical neuron excitability, and such a regulation could be mediated by specific adrenergic and dopaminergic receptors. We characterized electrophysiologically some of the types of responses to the iontophoretic application of adrenergic and dopaminergic agonists and antagonists on single cells in the rat visual cortex (areas occipital 1 monocular or Oc1M and occipital 1 binocular or Oc1B). For the majority of spontaneously active and visual cortical cells, noradrenaline and dopamine decreased the firing frequency. In the case of visually driven (synaptically activated) neurons, background firing was the main component of the response to be inhibited by the administration of noradrenaline, clonidine, and oxymetazoline, leading to an enhancement of the signal-to-noise ratio. Since these effects could be reduced or blocked by a previous ejection of the specific alpha 2-antagonist idazoxan, the findings support a role for alpha 2-adrenergic receptors in the transmission of sensory inputs to the visual cortex. These effects were not found with the mixed alpha-adrenergic agonist phenylephrine nor with the beta-agonist isoproterenol. Finally, the use of the inhibitory amino acid GABA rules out a simple hyperpolarizing response as the mechanism underlying noradrenaline modulatory effects in the cerebral cortex.
儿茶酚胺类物质去甲肾上腺素和多巴胺被认为是皮质神经元兴奋性的神经调质，这种调节可能由特定的肾上腺素能和多巴胺能受体介导。我们通过电生理学方法对大鼠视觉皮层（枕叶1单眼区或Oc1M和枕叶1双眼区或Oc1B）单个细胞上离子电渗法施加肾上腺素能和多巴胺能激动剂及拮抗剂的某些反应类型进行了表征。对于大多数自发活动的视觉皮层细胞，去甲肾上腺素和多巴胺会降低放电频率。对于视觉驱动（突触激活）的神经元，背景放电是去甲肾上腺素、可乐定和羟甲唑啉给药抑制反应的主要成分，从而导致信噪比提高。由于这些效应可被预先注入的特异性α2拮抗剂咪唑克生减弱或阻断，这些发现支持α2肾上腺素能受体在感觉输入向视觉皮层传递中的作用。混合性α肾上腺素能激动剂去氧肾上腺素和β激动剂异丙肾上腺素未发现这些效应。最后，使用抑制性氨基酸γ-氨基丁酸排除了简单的超极化反应作为去甲肾上腺素在大脑皮层调节作用基础的机制。
