title: Calcium alters the sensitivity of intact horizontal cells to dopamine antagonists.
abstract: Horizontal cells of the carp retina possess dopamine receptors linked to adenylate cyclase. Isolated, intact horizontal cells respond to micromolar concentrations of dopamine, whereas nanomolar concentrations of haloperidol, (+)-butaclamol, and flupenthixol block the dopamine response. Preincubation in Ringer's solution containing increased levels of Ca2+ (5-110 mM) decreases the sensitivity of the cells to these antagonists by 1,000-10,000 times. Dopamine sensitivity of the cells is not affected by Ca2+ levels in the preincubation medium. Preincubation of the cells in Ringer's solution containing 500 microM L-glutamate, an agent that increases intracellular Ca2+ levels in intact horizontal cells, also decreases the sensitivity of the cells to haloperidol. These data suggest that antagonist sensitivity of intact horizontal cells may be regulated by intracellular Ca2+.
mesh_terms: D000818:Animals; D002069:Butaclamol / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D002347:Carps; D000242:Cyclic AMP / Q000378:metabolism; D004298:Dopamine / Q000494:pharmacology; D018492:Dopamine Antagonists; D005475:Flupenthixol / Q000494:pharmacology; D005971:Glutamates / Q000494:pharmacology; D006220:Haloperidol / Q000494:pharmacology; D012160:Retina / Q000166:cytology / Q000187:drug effects* / Q000502:physiology
chemical_list: D018492:Dopamine Antagonists; D005971:Glutamates; D002069:Butaclamol; D000242:Cyclic AMP; D005475:Flupenthixol; D006220:Haloperidol; D002118:Calcium; D004298:Dopamine