Abstract
Xenopus oocytes has been utilized to analyze the intracellular signaling and coupling mechanisms between neurotransmitter receptors and ion channels. (1) The GTP-binding protein-coupled intracellular signaling pathway was analyzed in oocytes expressing metabotropic receptors by brain mRNA. These metabotropic receptors are commonly linked to the sequence of phosphoinositide metabolism, intracellular Ca2+ increase and opening of Ca2+-dependent Cl- channels. An antisense DNA study indicated that a specific subtype of GTP-binding protein is involved in the coupling of each metabotropic receptor. (2) Effects of central acting drugs on the functions of glutamate receptor subtypes and voltage-dependent Ca2+ channels were evaluated, and the data were compared with the results from conventional in vitro assays using brain preparations. (3) A series of experiments on κ-opioid receptors indicated that is κ-opioid receptors can couple with multiple signaling systems in the oocytes via GTP-binding proteins Gi/Go, which involves mobilization of intracellular Ca2+ through phosphoinositide metabolism, synergistic potentiation of cyclic AMP production, and inhibition of voltage-dependent Ca2+ channels.
