gamma-Preprotachykinin-(72-92)-peptide amide: an endogenous preprotachykinin I gene-derived peptide that preferentially binds to neurokinin-2 receptors.

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Abstract
The presence of N-terminally extended forms of neurokinin A has recently been reported in the mammalian brain. Among them, .gamma.-preprotachykin-(72-92)-peptide amide [.gamma.-PPT-(72-92)-NH2], a peptide derived by posttranslational processing of .gamma.-preprotachykinin, is most prominent. We report here that this peptide most likely acts on neurokinin-2 receptor sites since neurokinin A (a putative neurokin-2 agonist) and .gamma.-PPT-(72-92)-NH2 are potent competitors of 125I-labeled .gamma.-PPT-(72-92)-NH2 binding whereas selective neurokinin-1 and -3 agonists are not. Moreover, the distribution of 125I-labeled .gamma.-PPT-(72-92)-NH2 and 125I-labeled neurokinin A binding sites are very similar in rat brain. On the other hand, 125I-labeled Bolton-Hunter-substance P (a neurokinin-1 ligand) and 125I-labeled Bolton-Hunter-eledoisin (a neurokinin-3 ligand) binding sites are differentially located in this tissue. Thus, it appears that .gamma.-PPT-(72-92)-NH2 binds to neurokinin-2 receptors and should be considered as a putative endogenous ligand for this receptor class.