Question: What hormone produced by both the adrenal glands and certain neurons is released by chromaffin cells?

Small intensely fluorescent cells (SIF cells) are the interneurons of the sympathetic ganglia (postganglionic neurons) of the Sympathetic division of the autonomic nervous system (ANS).  The neurotransmitter for these cells is dopamine.  They are a neural crest derivative and share a common sympathoadrenal precursor cell with sympathetic neurons and chromaffin cells (adrenal medulla). <SEP> Chromaffin cells, also pheochromocytes, are neuroendocrine cells found mostly in the medulla of the adrenal glands in mammals.  These cells serve a variety of functions such as serving as a response to stress, monitoring carbon dioxide and oxygen concentrations in the body, maintenance of respiration and the regulation of blood pressure.  They are in close proximity to pre-synaptic sympathetic ganglia of the sympathetic nervous system, with which they communicate, and structurally they are similar to post-synaptic sympathetic neurons.  The chromaffin cells release catecholamines: ~80% of Adrenaline (Epinephrine) and ~20% of Noradrenaline (Norepinephrine) into systemic circulation for systemic effects on multiple organs (similarly to secretory neurones of the hypothalamus), and can also send paracrine signals.  In order to activate chromaffin cells, the splanchnic nerve of the sympathetic nervous system releases acetylcholine, which then binds to nicotinic acetylcholine receptors on the adrenal medulla.  This causes the release of catecholamines.  Hence they are called neuroendocrine cells. <SEP> Neuroendocrine cells are cells that receive neuronal input (neurotransmitters released by nerve cells or neurosecretory cells) and, as a consequence of this input, release message molecules (hormones) to the blood.  In this way they bring about an integration between the nervous system and the endocrine system, a process known as neuroendocrine integration.  An example of a neuroendocrine cell is a cell of the adrenal medulla (innermost part of the adrenal gland), which releases adrenaline to the blood.  The adrenal medullary cells are controlled by the sympathetic division of the autonomic nervous system.  These cells are modified postganglionic neurons. Autonomic nerve fibers lead directly to them from the central nervous system.  The adrenal medullary hormones are kept in vesicles much in the same way neurotransmitters are kept in neuronal vesicles.  Hormonal effects can last up to ten times longer than those of neurotransmitters.  Sympathetic nerve fiber impulses stimulate the release of adrenal medullary hormones.  In this way the sympathetic division of the autonomic nervous system and the medullary secretions function together. <SEP>  Epinephrine is normally produced by both the adrenal glands and certain neurons. Epinephrine, also known as adrenalin or adrenaline, is a hormone, neurotransmitter, and medication.  It plays an important role in the fight-or-flight response by increasing blood flow to muscles, output of the heart, pupil dilation, and blood sugar.  It does this by binding to alpha and beta receptors.  It is found in many animals and some single cell organisms.  Napoleon Cybulski first isolated epinephrine in 1895.