Molecular properties of the glutamate receptor mediating synaptic excitation in rat hypothalamic neurons

AMPA-type glutamate receptors (GluRs) mediate synaptic excitation in networks of cultured rat hypothalamic neurons [18, 25]. Under voltage clamp the agonists quisqualate and AMPA induce current responses which consist of a maintained and/or transient component depending on the concentrations applied. The current-voltage relationship for both components is linear. The biphasic response patterns are due to receptor desensitization which is fast and does not require intracellular second messengers for its activation. Several GluR-subtype-encoding transcripts were found in these neurons using polymerase chain reaction (PCR) methods. While mRNAs encoding the GluR2 and 3 flip forms are expressed early, mRNAs encoding the GluR1, 2 and 3 flop forms and the GluR4 flip form appear only in cultures older than 3 weeks. By comparison to recombinant receptors, the properties of the native receptor can be accommodated by a heteromeric receptor containing GluR2 as one of the subunits.