Effect of adrenergic agonists on eicosanoid output from isolated rabbit choroid plexus and iris-ciliary body

Prostanoid production by rabbit choroid plexus (CP) and irisciliary body (ICB), and the effects of adrenergic agonists thereon, were studied in vitro. Immunoreactive prostaglandin (PG) E₂ was the major prostanoid released by both tissues; the output from ICB was some two orders of magnitude greater than from CP. Immunoreactive 6-keto PGF_1α and thromboxane (TX) B₂, the dehydration products of prostacyclin and TXA₂, respectively, were detected in smaller quantities.

Epinephrine stimulated the outputs of PGE₂ and 6-keto PGF_1α, but not of TXB₂, from both tissues.ICB responded to epinephrine concentrations of 10⁻⁴ and 10⁻⁵, while only 10⁻⁴ was effective in stimulating prostanoid synthesis in the CP. Phenylephrine, an adrenergic agonist, stimulated prostanoid output from the ICB, but not from the CP. It is concluded that adrenergic mechanisms stimulate the biosynthesis of prostanoids in the rabbit CP and ICB. The implications of such interactions to aqueous humor and cerebrospinal fluid dynamics, or to other processes in brain and ocular physiology, are discussed.