Pharmacological properties of isolated horizontal and bipolar cells from the skate retina

Retinal neurons were enzymatically and mechanically dissociated from adult skate retinas and maintained in cell culture for up to 14 days. Intracellular recordings were made from isolated horizontal and bipolar cells while neurotransmitters were applied via pressure ejection. L-Glutamate, quisqualate, kainate, and gamma-amino-butyric acid (GABA), when applied to horizontal cells, produced large (60 to 70 mV), long-lasting depolarizations. These responses appear to consist of at least two components: a graded depolarization and a Ca++-dependent regenerative component. As regards bipolar cells, L-glutamate and its analogues depolarized about 30% of the cells tested, while GABA hyperpolarized most of these neurons. Both agents acted on bipolar cells by increasing conductance. Repeated applications of L-glutamate, quisqualate, kainate, and GABA to horizontal cells produced no desensitization, but in these circumstances the glutamate analogues, kainate and quisqualate, induced certain morphological changes, most notably a retraction of cell processes and the appearance of blebs on the cell surface.