Fig. 1.

Representative gel images of RT-PCR analysis of total RNA using primers specific for each of the known human dopamine D₂-like receptor subtypes (D₂, D₃, and D₄). Total RNA extracted from primary cultures of human airway smooth muscle (HASM) cells or freshly dissected human tracheal airway smooth muscle was analyzed. Lane 1: base pair standards; lane 2: negative control water blanks; lane 3: total RNA from primary cultured HASM cells; lane 4: total RNA from freshly dissected native human airway smooth muscle; lane 5: total RNA from whole human brain.