Tachykinins are active peptides which excite neurons, evoke behavioral responses, are potent vasodilators and secretagogues, and contract (directly or indirectly) many smooth muscles. Substance P produces a voltage-dependent inhibition of calcium current in retinal bipolar cells. It can enhance learning and memory, may regulate social approach and feeding behaviors, and can accelerate the functional recovery in postural balance in response to light after unilateral labyrinthectomy. Expressed in all parts of the brain, with robust expression in the olfactory bulbs and tracts, moderate expression in the hypothalamus and posterior brain, and weak expression in the telencephalon-preoptic region and optic tectum-thalamus. Also expressed in nerve fibers, intestine, testes and pituitary gland. Not expressed in the liver or kidneys. Expressed in the brain throughout development, with expression first observable in the nascent diencephalon, olfactory bulbs and hypothalamus shortly after fertilization. Expression is induced in the hypothalamus and olfactory bulb after feeding. Neuropeptide gamma contains alpha-helical structures at the C-terminus which may be required for interaction with a cognate receptor. Belongs to the tachykinin family.