Heterologous expression of metabotropic glutamate receptors in adult rat sympathetic neurons: Subtype-specific coupling to ion channels

Abstract

A novel heterologous expression system was used to examine the coupling of metabotropic glutamate receptors (mGluRs) to neuronal voltage-gated ion channels. Cytoplasmic injection of mGIuR2 cRNA into adult rat sympathetic neurons resulted in the expression of receptors that negatively coupled to N-typ ertussis toxin-sensitive pathway. Injection of mGIuR1α cRNA resulted in the expression of receptors that inhibited M-type K⁺ channels via a pertussis toxin-insensitive pathway. Coupling was restricted to specific transduction elements and effectors, since mGIuR2 did not inhibit M channels and mGIuR1α had minimal effects on Ca²⁺ channels. These findings demonstrate that heterologously expressed, and thus unambiguously identified, mGIuR subtypes modulate specific neuronal ion channels through discrete signal transduction pathways.