Also found in: Dictionary, Thesaurus, Encyclopedia.
The wide synaptic terminal of a cone photoreceptor located in the outer molecular (outer plexiform) layer of the retina. There are deep pits (invaginations) in the base of the terminal that contain the dendrites of bipolar and horizontal cells, often two of the former and one of the latter, in each invagination. The neurotransmitter is glutamate, which is stored in vesicles contained in the terminals, and when the photoreceptors are stimulated by light the release of glutamate is decreased. See cone cell; hyperpolarization; neuro-transmitter.