Neuropeptides signaling through G-protein alpha-i & G-protein alpha-q
Neuropeptide signaling through G-protein alpha-i & G-proteinalpha-q The signaling through G-protein alpha-i system is involved in many inhibitorycircuits in the brain. Neuropeptide activation of alpha-i G-protein-coupled receptorsgenerally leads to inhibition of cell excitability and release of neurotransmitters. Incase of opioids, this scenario leads to inhibition of pain transmission resulting inanalgesia. Neuropeptides are in tight interplay with each other. For example,opioid-induced analgesia could be modulated by Neuropeptide FF . Wide range of physiological and behavioral events is regulated by neuropeptidesthrough G-protein alpha-i and G-protein alpha-q pathways. Orexinsmodulate feeding behaviour and energy homeostasis, as well as associated drinkingbehaviours. They also regulate the sleep-wake cycle. The peptidic neurotransmitterNeuropeptide Y, the most abundant peptide in the mammalian brain, is involved inthe regulatory loops that control food intake in the hypothalamus. It appears to beimportant for regulating the activity of neuroendocrine axes under poor metabolicconditions, and exerts vasoconstrictive action . CNS effects ofNeuromedin B include effects on thermoregulation; regulation of TSH release,inhibition of feeding, stimulation of various CNS neurons, behavioral effects; andeffects on spinal sensory transmission . Neuromedin U was firstisolated based on its ability to contract rat uterine smooth-muscle (hence the suffix"U") and has since been implicated in the regulation of smooth-muscle contraction, bloodpressure and local blood flow, ion transport in the gut, stress responses, cancer,gastric acid secretion, pronociception, and feeding behavior .Substance P belongs to tachykinin peptide family and is involved in nociceptionand neuroimmunomodulation, as well as development of diseases such as bronchial asthma,inflammatory bowel syndrome and psychiatric disorders , .