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Curr Biol 2022 Mar 14;325:1038-1048.e2. doi: 10.1016/j.cub.2022.01.012.
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Bimodal modulation of short-term motor memory via dynamic sodium pumps in a vertebrate spinal cord.

Hachoumi L , Rensner R , Richmond C , Picton L , Zhang H , Sillar KT .

Dynamic neuronal Na+/K+ pumps normally only respond to intense action potential firing owing to their low affinity for intracellular Na+. Recruitment of these Na+ pumps produces a post-activity ultraslow afterhyperpolarization (usAHP) up to ∼10 mV in amplitude and ∼60 s in duration, which influences neuronal properties and future network output. In spinal motor networks, the usAHP underlies short-term motor memory (STMM), reducing the intensity and duration of locomotor network output in a manner dependent on the interval between locomotor bouts. In contrast to tonically active Na+ pumps that help set and maintain the resting membrane potential, dynamic Na+ pumps are selectively antagonized by low concentrations of ouabain, which, we show, blocks both the usAHP and STMM. We examined whether dynamic Na+ pumps and STMM can be influenced by neuromodulators, focusing on 5-HT and nitric oxide. Bath-applied 5-HT alone had no significant effect on the usAHP or STMM. However, this is due to the simultaneous activation of two distinct 5-HT receptor subtypes (5-HT7 and 5-HT2a) that have opposing facilitatory and suppressive influences, respectively, on these two features of the locomotor system. Nitric oxide modulation exerts a potent inhibitory effect that can completely block the usAHP and erase STMM. Using selective blockers of 5-HT7 and 5-HT2a receptors and a nitric oxide scavenger, PTIO, we further provide evidence that the two modulators constitute an endogenous control system that determines how the spinal network self-regulates the intensity of locomotor output in light of recent past experience.

PubMed ID: 35104440
PMC ID: PMC9616794
Article link: Curr Biol
Grant support: [+]

Species referenced: Xenopus laevis

References [+] :
Allen, Insights into the regulation of 5-HT2A serotonin receptors by scaffolding proteins and kinases. 2008, Pubmed