Ionotropic glutamate receptor that functions as a cation- permeable ligand-gated ion channel, gated by L-glutamate and the glutamatergic agonist kainic acid (PubMed:7536611, PubMed:8730589, PubMed:14511640). L-glutamate acts as an excitatory neurotransmitter at many synapses in the central nervous system (By similarity). Binding of the excitatory neurotransmitter L-glutamate induces a conformational change leading to the opening of the cation channel, converting the chemical signal to an electrical impulse (By similarity). The receptor then desensitizes rapidly and enters a transient inactive state, characterized by the presence of bound agonist (PubMed:14511640, PubMed:28180184, PubMed:34375587, PubMed:7536611, PubMed:8730589). Modulates cell surface expression of NETO2 (By similarity). In association with GRIK3, involved in presynaptic facilitation of glutamate release at hippocampal mossy fiber synapses (By similarity). {ECO:0000250|UniProtKB:P39087, ECO:0000269|PubMed:14511640, ECO:0000269|PubMed:28180184, ECO:0000269|PubMed:34375587, ECO:0000269|PubMed:7536611, ECO:0000269|PubMed:8730589}. Independent of its ionotropic glutamate receptor activity, acts as a thermoreceptor conferring sensitivity to cold temperatures (PubMed:31474366). Functions in dorsal root ganglion neurons (By similarity). {ECO:0000250|UniProtKB:P39087, ECO:0000269|PubMed:31474366}. This is the function of ENSG00000164418 (GRIK2, glutamate ionotropic receptor kainate type subunit 2).