RE responds to lighter stimuli after nerve injury

SNI RE glutamate-associated populations respond clearly to lighter mechanical stimulation, while sham mice chiefly respond to stronger stimulation. Heat-response peaks are comparable but latency is shorter after injury.

Open-arm entry and air-puff responses are greater after SNI, while unfamiliar-juvenile sniffing responses do not significantly differ. Injury affects selected contexts rather than all responses uniformly.

Original figure 1RE calcium across sensation and context

RE activation changes thresholds and behavior

Optical RE activation in normal mice lowers bilateral mechanical thresholds and heat latency, produces stimulation-context aversion, reduces social sniffing and increases tail-suspension/swimming immobility.

Place-test speed does not significantly change. Sensory outcomes and choices are modifiable by RE recruitment, motivating inhibition tests after nerve injury.

Original figure 2Sensory and behavioral RE-activation outcomes

Lowering RE activity improves model responses

Mechanical/heat hypersensitivity emerges soon after injury and persists. At four weeks, reduced novel-mouse investigation and increased immobility accompany it, motivating sensory, place-choice and social measures.

After SNI, RE cells fire more readily in slices. Further activation does not lower model thresholds further, whereas inhibition raises mechanical thresholds and heat latency. The same inhibition leaves normal-mouse thresholds unchanged.

SNI mice prefer the inhibition-paired context, sniff more and show less immobility, without significant place-test speed changes. Selected outcomes are also verified in female SNI mice, linking effects to injury state.

Original figure 3SNI outcomes after RE inhibition

Stronger input accompanies greater local inhibition

Tracing and recordings show direct RE excitation of vlPAG-projecting prefrontal cells and local GABA cells, which provide indirect inhibition onto projection cells.

Both currents grow after SNI, with a higher inhibitory/excitatory ratio and less projection-cell firing to RE stimulation. GABA-related blockade removes the firing difference, linking input recruitment to output regulation.

Original figure 4Direct excitation, indirect inhibition and SNI changes

RE-terminal modulation reproduces state-dependent effects

Unilateral RE-terminal activation in mPFC increases ipsilateral sensitivity without significant contralateral changes. Terminal inhibition in normal mice leaves thresholds, place choices and immobility unchanged.

In SNI, terminal inhibition raises thresholds, produces paired-context preference, increases social investigation and reduces immobility, with similarly directed female validation. Population and terminal outcomes converge on this prefrontal input.

Reducing prefrontal input enhances vlPAG responses

During RE–mPFC inhibition, vlPAG glutamate-associated populations respond more strongly to ipsilateral mechanical/heat stimuli, without equivalent significant contralateral changes.

The result accords with stronger local inhibition: reducing excessive input can strengthen a downstream response. Threshold and activity directions depend on the observed population and circuit stage.

Original figure 6Ipsilateral and contralateral vlPAG calcium

The input remains modifiable after tolerance

Chemogenetic inhibition of mPFC-projecting RE populations improves SNI sensory measures alone and augments lower-dose morphine threshold effects. After repeated morphine reduces drug efficacy, circuit inhibition still raises mechanical thresholds.

After repeated morphine, first evoked excitatory currents increase in both prefrontal projection and GABA cells, while paired-pulse ratios do not significantly change, adding synaptic observations alongside post-tolerance behavioral results.

Terminal-inhibition effects persist under tested naloxone conditions. This chiefly male study with selected female validation links injury-associated sensitivity and accompanying behavior to strengthened prefrontal input with greater local inhibitory recruitment.

Original figure 7Circuit inhibition during acute/repeated morphine exposure