Chromaffin cells, adrenal neurotransmitter release

Adrenaline (epinephrine) is a catecholamine, which is released as a neurotransmitter from neurons in the central nervous system and as a hormone from chromaffin cells of the adrenal gland. Adrenaline is required for increased metabolic and cardiovascular demand during stress. Its cellular actions are mediated via plasma membrane bound G-protein-coupled receptors. 

At least two classes of regulated secretion can be defined [54]. The standard regulated secretion pathway is common to all secretory cells (i.e. adrenal chromaffin cells, pancreatic beta cells, etc.) and works on a time scale of minutes or even longer in terms of both secretory response to a stimulus and reuptake of membranes after secretion. The second, much faster, neuron-specific form of regulated secretion is release of neurotransmitters at the synapse. Release of neurotransmitters may occur within fractions of a second after a stimulus and reuptake is on the order of seconds. Indeed, synaptic vesicles may be recycled and ready for another round of neurotransmitter release within 1-2 minutes [64]. These two classes of regulated secretion will be discussed separately after a consideration of secretory vesicle biogenesis. 

Two main pathways lead to the modulation of neurotransmitter release by inhibitory P2Y receptors, both involving modulation of VSCC. The first pathway, mediated by Gl /() proteins, results in PTX-sensitive, voltage-dependent inhibition of VSCC by the G-protein py subunits (Delmas et al. 1999 Dolphin 2003 mechanism 1 in Figure 3). Evidence for this pathway was initially obtained in adrenal chromaffin cells, where ATP and ADP reduced Ca2+ currents through activation of receptors... 

Pitta Bauermann et al. have applied constant distance shear force-controlled SECM to elec-trochemically image fibroblasts and adrenal chromaffin ceUs. In the case of the catecholamine-releasing chromaffin cells, the authors succeeded in amperometrically detecting the release of neurotransmitters from a single secretory vesicle, following chemical stimulation. 

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