Peptidergic signalling

Kalra, S.P. and Kaha, P.S. (1990) Neuropeptide Y a novel peptidergic signal for the control of feeding behavior. Current Topics in Neuroendocrinology, 110, 192-217. 

Rashid, A. J., O Dowd, B. F., and George, S. R. (2004) Minireview diversity and complexity of signaling through peptidergic G protein-coupled receptors. Endocrinology. 145, 2645-2652. 

Unlike 1,2,4- and 1,3,4-oxadiazoles, the 1,2,4-triazole heterocycle has the possibility of existing in different tautomeric forms (Scheme 20). X-ray crystal analysis of the peptide-based triazole 63 showed only one tautomerJ102 Additionally, the 13C NMR spectrum for this compound indicated only one tautomeric form since the signals due to C3 and C5 appeared as sharp peaks. This is not the case for some other peptidergic triazoles (Table 5) where peaks corresponding to C3 and C5 were broad and of low intensity or not visible. Differences in tautomeric preferences have been explained by the ability of some triazole-containing peptides to form intermolecular hydrogen bonds and thus stabilize one tautomer over the other. 

A major step forward, which extended our understanding of the range of neuropeptide activities, occurred after the advent of electron microscopy. The observation of synapse-like ("synaptoid") contacts between peptidergic neuron terminals and endocrine cells (in the corpus allatum as well as the adenohypophysis) clearly indicated that close-range signals from neural to endocrine cells contribute to the process of neuroendocrine communication. Subsequently, such peptidergic contacts turned out not to be restricted to endocrine cells they also occur on various somatic cells. 

At this juncture, a new type of interneuronal communication, i.e., the capacity of neuropeptides to act as neurotransmitters, had become established. Moreover, the structural parameters of peptidergic innervation were seen to include junctional complexes between two peptidergic neurons that seem to enable a reciprocal exchange of signals. 

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