Thimerosal is a mercury-containing vaccine preservative, which is currently considered one of the suspected causative agents of neurodevelopmental disorders.

Thimerosal increases the density of μ‑opioid receptors (MOR) in the periaqueductal gray (PAG) in a dose-dependent manner. High-dose thimerosal significantly elevates MOR density in the dorsomedial periaqueductal gray (DMPAG) and lateral periaqueductal gray (LPAG). At a dose of 3000 μg Hg/kg, thimerosal also increases MOR density in the caudate putamen (CPU). In contrast, two higher doses of thimerosal reduce MOR density in the dentate gyrus (DG) [1].
Four intramuscular injections (240 μg Hg/kg) on postnatal days 7, 9, 11, and 15 induce persistent changes in amino acid efflux: elevated glutamate and aspartate levels, accompanied by decreased glycine and alanine levels. These changes remain detectable 10–14 weeks after injection. Four injections of thimerosal at 12.5 μg Hg/kg do not significantly alter glutamate and aspartate concentrations measured by microdialysis. Application of thimerosal to the prefrontal cortex (PFC) via perfusion fluid rapidly increases glutamate efflux.
Coadministration of the neurosteroid dehydroepiandrosterone sulfate (DHEAS; 80 mg/kg; intraperitoneal injection) blocks the effects of thimerosal on glutamate and aspartate, whereas administration of the steroid alone has no significant effect on these amino acids. Coadministration of DHEAS and thimerosal in the perfusion fluid also blocks the acute effect of thimerosal on glutamate [2].

H2O: 80 mg/mL (197.62 mM), Sonication is recommended.