Anatomical distribution and cellular basis for high levels of aromatase activity in the brain of teleost fish: aromatase enzyme and mRNA expression identify glia as source

Although teleost fish have higher levels of brain aromatase activity than any other vertebrate group, its function remains speculative, and no study has identified its cellular basis. A previous study determined aromatase activity in a vocal fish, the plainfin midshipman (Porichthys notatus), and found highest levels in the telencephalon and lower levels in the sonic hind-brain, which was dimorphic between and within (males) sexes. We have now localized aromatase-containing cells in the mid-shipman brain both by immunocytochemistry using teleost-specific aromatase antibodies and by in situ hybridization using midshipman-specific aromatase probes. Aromatase-immuno-reactivity and mRNA hybridization signal are consistent with relative levels of aromatase activity in different brain regions: concentrated in the dimorphic sonic motor nucleus, in a band just beneath the periaqueductal gray in the midbrain, in ven