Identification of neuropeptide Y receptors in cultured astrocytes from neonatal rat brain

Specific binding sites for neuropeptide Y could be demonstrated in primary cultures of astrocytes from neonatal rat brain. Neuropeptide Y binding was saturable, reversible, and temperature dependent as revealed by saturation studies and kinetic experiments. Scatchard analysis of equilibrium binding data indicated a single population of high‐affinity binding sites with respective K D and B max values of 0.43 nM and 6.9 fmol/2.7 × 10 5 cells. Physiological responses induced by neuropeptide Y could be detected in a distinct subpopulation of cultured astrocytes on the basis of two criteria: (1) electrophysiological responses and (2) single cell measurements of changes in [Ca 2+ ] i . In that fraction of cells responding (20–70%, varying among cultures from different preparations), brief application of neuropeptide Y led to a membrane potential depolarization, lasting several minutes. When the membrane was clamped close to the resting membrane potential using the whole‐cell patch‐clamp technique, neuropeptide Y induced an inward current with a similar time course as the neuropeptide Y‐induced membrane depolarization. As detected by single cell microfluorimetric (fura‐2) measurements neuropeptide Y induced an increase of [Ca 2+ ] i which was caused by the entry of extracellular Ca 2+ . Both the [Ca 2+ ] i increase and the electrophysiological responses were unaffected by pretreatment of the astrocytes with pertussis toxin. © 1993 Wiley‐Liss, Inc.