Optoactivation of parvalbumin neurons in the spinal dorsal horn evokes GABA release that is regulated by presynaptic GABAB receptors.
Among heterogeneous neural cells in the spinal dorsal horn, parvalbumin (PV)-positive neurons are one subtype of GABA (γ-aminobutyric acid)-containing interneurons. Using an optogenetic approach, we expressed blue light-sensitive cation channel channelrhodopsin-2 (ChR2) via a viral vector on PV neurons in the spinal dorsal horn. Combined with in vitro whole-cell recordings, we activated ChR2 expressed on PV neurons by blue light and recorded GABAA receptor-mediated light-evoked inhibitory postsynaptic currents (L-IPSCs). The L-IPSCs were action potential-dependent and abolished by the GABAA receptor antagonist picrotoxin, indicating a synchronic GABA release from presynaptic terminals. Activation of GABAB receptors (the metabotropic receptors of GABA) on presynaptic terminals by a putative agonist, baclofen, depressed the amplitude of L-IPSCs. This depression was largely occluded by pretreatment with the highly selective Cav2.1 (P/Q-type) Ca(2+) channel blocker ω-agatoxin IVA. N-type Ca(2+) channel blocker ω-conotoxin GVIA showed less effects on either L-IPSCs or baclofen depression. We conclude that optoactivation of PV-ChR2 neurons in the spinal dorsal horn induces GABA release from presynaptic terminals, which is modulated by presynaptic GABAB receptors that are coupled to P/Q-type Ca(2+) channels. Importantly, our studies provide a simple and reliable optogenetic approach to study dorsal horn neural circuits.
['Yang|Kun|K|', 'Ma|Rui|R|', 'Wang|Qian|Q|', 'Jiang|Ping|P|', 'Li|Yun-Qing|YQ|']
D000818:Animals D000075402:Channelrhodopsins D005260:Female D008297:Male D008822:Mice, Transgenic D062308:Optogenetics D010320:Parvalbumins D020671:Posterior Horn Cells D018080:Receptors, GABA-B D017661:Receptors, Presynaptic D013376:Substantia Gelatinosa D005680:gamma-Aminobutyric Acid
GABA Optogenetics Whole-cell recordings Pain Spinal cord