Roerig B, Katz L C
Howard Hughes Medical Institute and Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710, USA.
J Neurosci. 1997 Nov 1;17(21):8324-38. doi: 10.1523/JNEUROSCI.17-21-08324.1997.
Serotonergic projections are widespread in the developing neocortex, but their functions are obscure. The effects of 5-HT3 receptor agonists on cortical circuit response properties were studied in slices of ferret primary visual cortex using high-speed optical imaging of voltage-sensitive dye signals and whole-cell patch-clamp recording. Activation of the 5-HT3 receptor decreased the amplitude and lateral extent of excitation throughout postnatal development. This effect peaks after eye opening, which indicates a function for serotonergic modulation of circuit responses during the period of refinement of cortical connections. Whole-cell patch-clamp recordings from single neurons revealed that synaptic responses evoked by white matter stimulation were reduced by 5-HT3 receptor agonists, whereas the frequency of spontaneous GABAergic synaptic currents was enhanced dramatically. This indicates that the modulation of spontaneous synaptic activity by fast-acting serotonin receptors is reflected in an inhibition of the circuit response, in line with the notion of background synaptic activity altering the spatiotemporal integration properties of cortical cells by changing their membrane potential and their electrotonic structure. These mechanisms may regulate the response properties of intrinsic circuits in both the adult and developing neocortex.
5-羟色胺能投射在发育中的新皮质中广泛分布，但其功能尚不清楚。我们使用电压敏感染料信号的高速光学成像和全细胞膜片钳记录技术，在雪貂初级视觉皮质切片中研究了5-HT3受体激动剂对皮质回路反应特性的影响。在整个出生后发育过程中，5-HT3受体的激活降低了兴奋的幅度和横向范围。这种效应在睁眼后达到峰值，这表明在皮质连接细化期间，5-羟色胺能对回路反应具有调节作用。对单个神经元的全细胞膜片钳记录显示，白质刺激诱发的突触反应被5-HT3受体激动剂减弱，而自发GABA能突触电流的频率则显著增加。这表明快速作用的5-羟色胺受体对自发突触活动的调节反映在对回路反应的抑制上，这与背景突触活动通过改变皮质细胞的膜电位和电紧张结构来改变其时空整合特性的观点一致。这些机制可能调节成年和发育中的新皮质中固有回路的反应特性。
