Neuronal Secretion

Constitutive secretion Regulated secretion Neuronal secretion... 

Greenfield, SA (1991) A noncholinergic action of acetylcholinesterase (AchE) in the brain. From neuronal secretion to the generation of movement. Cell. Mol. Neurohiol. 11 55-77. 

Hussein, A.S., Chacon, M.R., Smith, A.M., Tosado-Acevedo, R. and Selkirk, M.E. (1999a) Cloning, expression and properties of a non-neuronal secreted acetylcholinesterase from the parasitic nematode Nippostrongylus brasiliensis. Journal of Biological Chemistry 274, 9312-9319. 

Yu X, Duan KL, Shang CF, Yu HG, Zhou Z (2004) Calcium influx through hyperpolarization-activated cation channels (1(h) channels) contributes to activity-evoked neuronal secretion. Proc Natl Acad Sci USA 101 1051-6... 

Poulain DA, Wakerley JB (1982) Electrophysiology of hypothalamic magnocellular neurones secreting oxytocin and vasopressin. Neuroscience 7 773-808. 

Renaud LP, Bourque CW (1991) Neurophysiology and neuropharmacology of hypothalamic magnocellular neurons secreting vasopressin and oxytocin. Prog Neurobiol 36 131-169. 

Dopa, on the other hand, a precursor of dopamine, does cross the barrier, giving relief to many individuals with Parkinsonism. Dopaminergic neurons (neurons secreting dopamine) may be involved in schizophrenia. In this case, the neurons secrete too much dopamine. 

Serotonin affects motor activity by inhibiting the impact of sensory information and by coordinating autonomic and neuroendocrine function during demanding motor activity. Terminals of neurons secreting 5-HT are located in the primary and secondary motor areas of the brain. 

Most neurons communicate with one another by the secretion of chemical substances known as neurotransmitters. Neurotransmission occurs in a region known as the synapse which constitutes the input of one neuron and the output of the neuron secreting the transmitter. Since neurons form synapses throughout the brain, one would expect that the cellular heterogeneity would also be reflected in a chemical heterogeneity of neurotransmitter concentrations within the brain. This hypothesis can be tested for catecholamine neurotransmitters because carbon fiber microelectrodes Implanted in the brain can detect them voltammetrlcally. 

The antidiuretic hormone is secreted according to a first-order neuroendocrine mechanism. A central nervous system neuron secretes the active polypeptide, which is transported in the blood to the target organ. This assumption is based on the experiments of Horsley and Clarke, who destroyed the hypothalamic nuclei without affecting the hypophysis itself by approaching the thalamus from above. These experiments demonstrated that destruction of the supraoptic nuclei or of the fiber tracts that lead from these nuclei to the posterior lobe was consistently associated with diabetes insipidus. In contrast, total hypophysectomy does not necessarily induce diabetes insipidus. 

The adrenergic system is an essential regulator that increases cardiovascular and metabolic capacity during situations ofstress, exercise, and disease. Nerve cells in the central and peripheral nervous system synthesize and secrete the neurotransmitters noradrenaline and adrenaline. In the peripheral nervous system, noradrenaline and adrenaline are released from two different sites noradrenaline is the principal neurotransmitter of sympathetic neurons that innervate many organs and tissues. In contrast, adrenaline, and to a lesser degree noradrenaline, is produced and secreted from the adrenal gland into the circulation (Fig. 1). Thus, the actions of noradrenaline are mostly restricted to the sites of release from sympathetic nerves, whereas adrenaline acts as a hormone to stimulate many different cells via the blood stream. 

The first hormonal signal found to comply with the characteristics of both a satiety and an adiposity signal was insulin [1]. Insulin levels reflect substrate (carbohydrate) intake and stores, as they rise with blood glucose levels and fall with starvation. In addition, they may reflect the size of adipose stores, because a fatter person secretes more insulin than a lean individual in response to a given increase of blood glucose. This increased insulin secretion in obesity can be explained by the reduced insulin sensitivity of liver, muscle, and adipose tissue. Insulin is known to enter the brain, and direct administration of insulin to the brain reduces food intake. The adipostatic role of insulin is supported by the observation that mutant mice lacking the neuronal insulin receptor (NDRKO mice) develop obesity. 

Vasopressin (antidiuretic hormone [ADH]) secretion increases in response to decreased blood volume and/or reductions in effective blood volume via a decrease in inhibitory tone from both low-pressure and high-pressure baroreceptors to the hypothalamus. The neuronal pathways that mediate hemodynamic regulation of... 

CART (cocaine- and amphetamine-regulated transcript) is a hypothalamic peptide that inhibits both normal and starvation-induced feeding when injected into cerebral ventricles of rats. CART is co-localized with the anorexigenic peptide a-melanocyte-stimulating hormone in neurons of the arcuate nucleus. Secretion of CART is stimulated by leptin and CART may be an endogenous inhibitor of food intake. 

Excitability refers to the capacity of nerves and other tissues (e.g. cardiac), as well as individual cells, to generate and sometimes propagate action potentials, signals that serve to control intracellular processes, such as muscle contraction or hormone secretion, and to allow for long- and short-distance communication within the organism. Examples of excitable cells and tissues include neurons, muscle and endocrine tissues. Examples of nonexcitable cells and tissues include blood cells, most epithelial and connective tissues. 

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