Midbrain somatostatin-expressing cells control pain-suppression during defensive states.

Optogenetic activation of long-range SST+ vlPAG cells projecting to the RVM abolishes fear-linked analgesia in male mice, while inhibition promotes analgesia regardless of defensive state.

• Why it matters: Endogenous pain suppression is critical for adaptive defensive behavior, but the specific neuronal circuit mechanisms that emotionally regulate analgesia remain unclear.
• What they did: Using behavioral testing, anatomical mapping, optogenetics, and electrophysiology in male mice, the study manipulated SST+ cells in the ventrolateral periaqueductal gray and their projections to the rostral ventromedial medulla.
• The result: A long-range SST+ vlPAG→RVM circuit is identified as regulating analgesia during defensive states, implying emotional context determines whether this pathway supports or suppresses pain inhibition.

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