Co-expression of serotonin 5-HT1B and 5-HT4 receptors in p11 containing cells in cerebral cortex, hippocampus, caudate-putamen and cerebellum

► p11 is expressed in both interneurons and principal projecting neurons. ► p11 containing cells co-expressed 5-HT1BR and/or 5-HT4R in several brain regions. ► p11 appears anatomically positioned to modulate serotonin neurotransmission.