Effect of Hypothalamic Proline-Rich-Polypeptide on Voltage-Gated Ca2+ Currents in Retinal Ganglion Cells

Neurotrophins are molecules that regulate neuronal survival, nervous system plasticity, and many other physiological functions of neuronal and glial cells. Here we studied the physiological action of a novel neurosecretory polypeptide proline-rich polypeptide (PRP), isolated from bovine neurohypophysis neurosecretory granules, on voltage-gated Ca currents and spike firing activity of retinal ganglion cells. PRP reversibly increased high voltage–activated L-type Ca current, but was without effect on low voltage–activated T-type current. PRP also increased the spike after hyperpolarization and reduced the frequency of spike firing, most likely by affecting a Ca-dependent potassium current.