Neuronal polyamine-transporter involved in pain perception (PubMed:40836097, PubMed:41075780). Transports polyamines such as putrescine, cadaverine, spermine and spermidine (PubMed:40836097, PubMed:41075780). Expressed in sensory neuron subtypes within the dorsal root ganglion, where it regulates the excitability of C- polymodal nociceptors by mediating polyamine transport (By similarity). {ECO:0000250|UniProtKB:Q0P5V9, ECO:0000269|PubMed:40836097, ECO:0000269|PubMed:41075780}. This is the function of Ensembl gene identifier ENSG00000022567 (SLC45A4, solute carrier family 45 member 4).