ABSENCE OF KCTD16 WEAKENS GABA<SUB>B</SUB> RECEPTOR-MEDIATED INHIBITORY SYNAPTIC TRANSMISSION IN SPINAL DORSAL HORN NEURONS

GABA_B receptors mediate slow synaptic inhibition and are key regulators of nociceptive transmission in the spinal dorsal horn. Their signalling efficacy is shaped by auxiliary KCTD proteins, yet the impact of KCTD16 on inhibitory circuits controlling pain remains unknown.
Using patch‑clamp recordings in acute spinal cord slices, we examined excitatory (EPSC) and inhibitory (IPSC) currents in lamina I–II neurons from wild-type (WT) and KCTD16^⁻/⁻ mice under naïve and inflammatory conditions. Miniature EPSCs and IPSCs were recorded to assess presynaptic release probability and GABA_B receptor modulation. Optogenetically evoked inhibitory postsynaptic currents (leIPSCs) were elicited via VGAT–ChR2 activation of inhibitory interneurons.
In WT neurons, baclofen significantly reduced mEPSC and mIPSC frequencies, reflecting suppression of excitatory and inhibitory inputs. In KCTD16^⁻/⁻ neurons, baclofen-induced inhibition was markedly attenuated, particularly at inhibitory synapses for mIPSC frequency and leIPSC amplitude. Under inflammatory conditions, excitatory drive was enhanced in both genotypes, yet GABA_B-mediated inhibition persisted only in WT neurons. KCTD16 deletion abolished sustained presynaptic inhibition and reduced GABA_B-mediated modulation of inhibitory currents.
KCTD16 critically supports GABA_B receptor effectivity in spinal cord dorsal horn. Its absence compromises inhibitory tone and responsiveness to GABA_B inhibitor baclofen, particularly under pathological conditions of increased afferent drive in peripheral inflammation pain model. These results highlight a synapse-specific regulatory role of KCTD16 in spinal inhibitory transmission and identify it as a key modulator of GABA_B receptor function in pain control. This work was supported by the Grant Agency of the Czech Republic (GACR 25-15684S).