Targeting Tools: Investigating the Itch Pathway

Bombesin-SAP (Cat. #IT-40)

Bombesin is a 14-amino-acid peptide found in frog-skin. The human equivalent, gastrin releasing peptide (GRP) has been detected in itch pathways and plays a role in eating behaviors. GRP regulates numerous functions of the gastrointestinal and central nervous systems, including release of gastrointestinal hormones, smooth muscle cell contraction, and epithelial cell proliferation.

Bombesin-SAP specifically targets GRP receptor-positive cells (Figure 1). All other cells are left untouched. Elimination of cells expressing GPR receptor is useful in studying the role of bombesin in itch and eating behaviors.

Effective Tool: Elimination of cells expressing GRP receptor is useful in studying the role of bombesin in itch and eating behaviors.


Figure 1. Selective ablation of GRPR+ neurons in the spinal cord. (A-B) GRPR expression detected by in situ hybridization significantly reduced in lamina I of mice. (C-D) NK1 receptor expression detected by immunocytochemistry in the dorsal horn was similar between the two groups. Scale bar: 100 μm.

Chen ZF, Sun YG, Zhao ZQ, Meng XL, Yin J, Liu XY (2009) Ablation of GRPR+ Neurons in the Spinal Cord by Bombesin-Saporin Knocks Out Itch Sensation in Mice Without Affecting Pain Circuit. Targeting Trends 10(4):1, 6.

Nppb-SAP (Cat. #IT-69)

Itch is triggered by somatosensory neurons expressing the ion channel TRPV1 (transient receptor potential cation channel subfamily V member 1). Neuropeptide natriuretic polypeptide b (Nppb) is expressed in a subset of TRPV1 neurons and research has found that Nppb lesioned mice selectively lose almost all behavioral responses to itch-inducing agents. Itch responses are blocked by toxin-mediated ablation of Nppb-receptor–expressing cells, but a second neuropeptide, gastrin-releasing peptide (Bombesin), still induces strong responses in the toxin-treated animals, an apparent downstream effect. Nppb-SAP eliminates cells expressing neuropeptide natriuretic polypeptide b (Nppb or BNP) receptor.

Mishra SK, Hoon MA. (2013) The cells and circuitry for itch responses in mice. Science 340(6135):968-971. (Targeting Trends 13q3)

NMB-SAP (Cat. #IT-70)

Neuromedin B (NMB) and GRP are two members of the mammalian bombesin family of peptides. These two peptides activate structurally similar but pharmacologically distinct G-protein-coupled receptors. NMB is expressed in a subset of sensory neurons that co-label with calcitonin gene-related peptide and TRPV1, suggestive of a role for NMB in nociception. NMB-SAP removes neurons expressing the NMB receptor. In the periphery NMB and GRP have a wide variety of actions including smooth muscle contraction and exocrine and endocrine functions. In the CNS these peptides regulate food intake and body temperature, as well as stress behavioral responses. Additionally, immunolocalization studies showed that NMB protein is present in the dorsal horn of the spinal cord and expression was also seen in sensory neurons.

Mishra SK, Holzman S, Hoon MA. (2012) A nociceptive signaling role for neuromedin B. J Neurosci 20(32):8686-8695. (Targeting Trends 12q4)