Neuropeptides: Biology and Regulation

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document in English

biology

research papers

published 26/11/2007

review : Completed

level : Advanced

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Summary

The past several decades have witnessed a veritable explosion of knowledge about the central nervous system (CNS), and in no area has this been as impressive as in peptide neurobiology. Numerous peptide neurotransmitter candidates have been identified and characterized, their CNS distributions mapped, and their genes cloned. The tenet “one neuron-one transmitter” erroneously attributed to Dale has been convincingly refuted with numerous demonstrations of neurons containing multiple peptides or combinations of peptide and nonpeptide neurotransmitters. Additionally, since the early 1980s there has been an embarrassment of riches in the form of knowledge about neurotransmitter receptor diversity, diversity of receptor-effector coupling, and neurotransmitter transporters. These discoveries have not yet been fully integrated into what is known about normal or aberrant CNS function, although dysfunction at virtually any level could conceivably lead to neuropsychiatric deficits.

By definition, a neuropeptide is a chain of two or more amino acids linked by peptide bonds, and differs from other proteins only in the length of the amino acid chain.
Many of the known behavioral effects of neuropeptides are observed only after their direct injection into the CNS because most peptides do not penetrate the blood-brain barrier in amounts sufficient to produce effects before being inactivated by serum and tissue enzymes that degrade them.
The tertiary structure for recognition is also used by the immune system for the production of specific antibodies, as well as by biological receptors.
Neuropeptides are found throughout the CNS, as well as in various peripheral organs, such as the gastrointestinal tract, pancreas, and adrenal glands.
In the cortex of rats SRIF is found in some of the large stellate-shaped neurons and in abundance among the fusiform-shaped, nonpyramidal neurons of layers II to V, and particularly in layer V of the sensory cortex.
Through the use of retrograde tracing methods and dual staining techniques, several pathways for certain peptides have now been delineated.
Some of the noradrenergic locus ceruleus neurons, in turn, project to the hypothalamic paraventricular nucleus where their input increases CRF synthesis and release.
The neurotensin-neuromedin N gene was originally cloned from canine ileal mucosa, and complementary deoxyribonucleic acid (cDNA) probes constructed against this form were used to clone the rat gene.