Baker Arielle L, Gulledge Allan T
1. Department of Molecular and Systems Biology Geisel School of Medicine at Dartmouth College Hanover, NH 03755.
bioRxiv. 2025 May 5:2025.05.04.652144. doi: 10.1101/2025.05.04.652144.
Acetylcholine (ACh) and serotonin (5-hydroxytryptamine, or 5-HT) differentially regulate the excitability of pyramidal neurons in the mouse prelimbic (PL) cortex according to their long-distance projections. We tested for afferent- and/or target-specific modulation of glutamate release by these neuromodulators in two key afferents to the PL cortex: commissural (COM) projections from the contralateral hemisphere and projections from the mediodorsal nucleus (MDN) of the thalamus. Using an ex-vivo optogenetic approach, we mapped the connectivity of COM and MDN afferents in intratelencephalic (IT) and extratelencephalic (ET) layer 5 projection neurons and tested for afferent-selective neuromodulation of synaptic transmission. Dual whole-cell recordings in pairs of IT and ET neurons found that COM afferents monosynaptically target both IT and ET neurons, but that MDN afferents selectively target IT neurons. Both afferents exhibited similar, and target-independent, short-term synaptic plasticity (facilitation), but were differentially modulated by ACh and 5-HT. COM transmission was suppressed strongly by ACh and moderately by 5-HT, while MDN inputs to IT neurons were largely unaffected by either neuromodulator. Cholinergic suppression of COM transmission was blocked by atropine or the M4-preferring antagonist VU602841, but enhanced by the M4 positive allosteric modulator VU0467154. Serotonergic suppression of COM transmission was mildly reduced in the presence of SB216691, a 5-HT receptor antagonist. Chemogenetic inhibition of hM4Di-expressing COM terminals mimicked the suppressive effects of ACh and 5-HT on synaptic transmission. These data demonstrate that, while ACh and 5-HT differentially regulate IT and ET excitability, they are similarly selective in regulating COM synaptic transmission in the PL cortex.
乙酰胆碱（ACh）和5-羟色胺（5-羟色胺，或5-HT）根据其长距离投射，对小鼠前边缘（PL）皮质中锥体神经元的兴奋性进行不同调节。我们测试了这些神经调质对PL皮质的两个关键传入神经中谷氨酸释放的传入特异性和/或靶标特异性调节：来自对侧半球的连合（COM）投射和丘脑背内侧核（MDN）的投射。使用离体光遗传学方法，我们绘制了COM和MDN传入神经在脑内（IT）和脑外（ET）第5层投射神经元中的连接性，并测试了突触传递的传入选择性神经调节。在成对的IT和ET神经元中进行双全细胞记录发现，COM传入神经单突触靶向IT和ET神经元，但MDN传入神经选择性靶向IT神经元。两种传入神经都表现出相似的、与靶标无关的短期突触可塑性（易化），但受到ACh和5-HT的不同调节。COM传递受到ACh的强烈抑制和5-HT的中度抑制，而MDN对IT神经元的输入在很大程度上不受这两种神经调质的影响。阿托品或M4选择性拮抗剂VU602841可阻断胆碱能对COM传递的抑制，但M4正变构调节剂VU0467154可增强这种抑制。5-HT受体拮抗剂SB216691存在时，5-羟色胺对COM传递的抑制作用略有降低。对表达hM4Di的COM终末进行化学遗传抑制模拟了ACh和5-HT对突触传递的抑制作用。这些数据表明，虽然ACh和5-HT对IT和ET兴奋性进行不同调节，但它们在调节PL皮质中COM突触传递方面具有相似的选择性。
