Neurotransmitters, insulin secretion modulation

Voltage-activated Ca " channels are activated by membrane depolarization and represent a large family of related channels with a wide tissue distribution. They are found ubiquitously in neurons, muscles, and endocrine cells as well as in many epithelial and endothelial cells. In addition to neurotransmitter release, they mediate a variety of essential functions in the body including muscle contraction, insulin secretion, gene expression, modulation of signal transduction events and in excess can cause cell death. 

Initiators of insulin secretion switch on the secretory machinery. Thereafter modulators derived from nutrient metabolism, hormones/peptides and neurotransmitters determine how fast or slow the machine will run. 

The most potent initiator of insulin secretion is glucose. Under physiological conditions its action is modulated by hormones, peptides and neurotransmitters as discussed later. 

MODULATION OF INSULIN SECRETION BY HORMONES. NEUROPEPTIDES AND NEUROTRANSMITTERS... 

As to be expected from a peptide that has been highly conserved during evolution, NPY has many effects, e.g. in the central and peripheral nervous system, in the cardiovascular, metabolic and reproductive system. Central effects include a potent stimulation of food intake and appetite control [2], anxiolytic effects, anti-seizure activity and various forms of neuroendocrine modulation. In the central and peripheral nervous system NPY receptors (mostly Y2 subtype) mediate prejunctional inhibition of neurotransmitter release. In the periphery NPY is a potent direct vasoconstrictor, and it potentiates vasoconstriction by other agents (mostly via Yi receptors) despite reductions of renal blood flow, NPY enhances diuresis and natriuresis. NPY can inhibit pancreatic insulin release and inhibit lipolysis in adipocytes. It also can regulate gut motility and gastrointestinal and renal epithelial secretion. 

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