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Tyler E. Girard

3 papers in the library · 17 citations · publishing 2025-2026

Papers

Ketamine evokes acute behavioral effects via μ-opioid receptor expressing neurons of the central amygdala.

Biological Psychiatry May 5, 2025 Matthew B Pomrenze, Sam Vaillancourt, Pierre Llorach et al. 11 citations

Ketamine produces a rapid increase in movement (locomotor activation) in mice by acting on mu opioid receptors (MORs) in the central amygdala (CeA). This effect is blocked by the opioid receptor antagonist naltrexone, and the same blockade occurs with a MOR-selective antagonist. Whole-brain imaging showed that naltrexone most strongly altered ketamine-induced cFos expression in the CeA, particularly in neurons that co-express MOR and PKCδ. Interrupting MOR function specifically in the CeA, either with a drug or genetic manipulation, prevented ketamine's locomotor effects. This indicates that ketamine's acute behavioral effects involve opioid signaling in the CeA, which may relate to its antidepressant mechanism in humans.

DOI: 10.1016/j.biopsych.2025.04.020 (opens in new tab) Full text (opens in new tab) Antidepressant Central amygdala Mu opioid receptor Naltrexone +5

No evidence of immediate or persistent analgesic effect from a single dose of psilocybin in three mouse models of pain

Nature Communications January 22, 2026 Nicholas Gregory, Tyler E. Girard, Akila Ram et al. 5 citations

Psilocybin, a psychedelic compound, was tested for direct pain-relieving effects in mice with inflammatory, nerve injury, and muscle pain. Across a range of doses (0.3, 2, and 10 mg/kg) in both sexes, using multiple sensory and functional pain tests, psilocybin showed no analgesic effect except for reduced cold sensitivity. That reduction likely resulted from psilocybin-induced hypothermia rather than true pain relief. The findings suggest that any lasting therapeutic benefits of psilocybin for chronic pain are not due to direct analgesic action.

DOI: 10.1038/s41467-026-68763-z (opens in new tab) Full text (opens in new tab) Psilocybin Analgesic Medicine Hallucinogen +10