Glossary

biosynthetic pathway A series of enzymatic reactions by which a substance is made.

cholinergic Denotes a neuron that uses acetylcholine as transmitter.

cholinoceptive Denotes a target cell with a receptor for acetylcho-line.

endoplasmic reticulum Polyprotein precursors of neuropeptides (and other secreted proteins) are translated from messenger RNA on polyribosomes attached to the cytoplasmic surface of the endoplas-mic reticulum, a series of membranous tubules. The nascent polypeptide chain is extruded into the lumen of these tubules, processed, and then sent to the Golgi apparatus in transport vesicles.

Golgi apparatus A complex structure consisting of a series of tubules arrayed in stacks. Its primary function is to process newly synthesized proteins and package them for transport to the external cell membrane.

receptors for neurotransmitters As a rule are transmembrane proteins located on the postsynaptic surface of a target cell. Ionotropic receptors form a channel for the passage of ions when they bind the transmitter. Metabotropic receptors interact with second messenger systems when the transmitter is bound, often through a G-protein. The receptors for some messengers (e.g., NO and arachidonic acid) are enzymes or factors within the target cell.

Chemical synaptic transmission is mediated by the release of one or more substances from a nerve terminal. About 100 neurotransmitters have been identified. These belong to two categories: neuropeptides and small molecules. Neurotransmitters produce their action by binding to receptors in target cells.

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