Tachyphylaxis (Greek ταχύς, tachys, "rapid", and φύλαξις, phylaxis, "protection") is a medical term describing an acute, sudden decrease in response to a drug after its administration; i.e. a rapid and short-term onset of drug tolerance. It can occur after an initial dose or after a series of small doses. Increasing the dose of the drug may be able to restore the original response. Characteristics
Tachyphylaxis is characterized by the rate sensitivity: the response of the system depends on the rate with which a stimulus is presented. To be specific, a high-intensity prolonged stimulus or often-repeated stimulus may bring about a diminished response also known as desensitization. Molecular interaction
In biological sciences, molecular interactions are the physical bases of the operation of the system. The control of the operation, in general, involves interaction of a stimulus molecule with a receptor/enzyme subsystem by, typically, binding to the macromolecule A and causing an activation or an inhibition of the subsystem by forming an activated form of the macromolecule B.
A gangliocytic paraganglioma  is a rare tumour that is typically found in the duodenum and consists of three components: (1) ganglion cells, (2) epithelioid cells (paraganglioma-like) and, (3) spindle cells (schwannoma-like). Symptoms and signs
The most common presentation is gastrointestinal bleed (~45% of cases), followed by abdominal pain (~43% of cases) and anemia (~15% of cases). Pathology
GP consist of three components (1) ganglion cells, (2) epithelioid cells (neuroendocrine-like), and (3) spindle cells (schwannoma-like). The microscopic differential diagnosis includes poorly differentiated carcinoma, neuroendocrine tumour and paraganglioma.GPs may be sporadic or arise in the context neurofibromatosis type 1. See also
Schwannoma
Paraganglioma


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