Figure 1. Expression of MT1 receptors and activation of Gα_q by melatonin in gastric smooth muscle cells.

(A) RT-PCR. Total RNA isolated from cultured (first passage) rabbit gastric muscle cells and the brain was reverse transcribed, and cDNA was amplified with specific primers for MT₁ or MT₂. Experiments were done in the presence (+ RT) or absence (−RT) of reverse transcriptase (RT). PCR product with predicted size was obtained in the presence of reverse transcriptase with primers for MT₁ (194 bp), but not with primers for MT₂, in smooth muscle cells (SMC), whereas PCR products were obtained with primers for MT₁ (194 bp) and MT₂ (392 bp) in the brain. (B) Western blot. Lysates prepared from dispersed smooth muscle cells (lane 1), cultured gastric smooth muscle cells (lane 2), and the brain (lane 3) of rabbit were run on SDS-PAGE and analyzed by western blot. Proteins were probed with polyclonal antibodies to MT₁ (1:1000) or MT₂ (1:1000). A protein band corresponding to 40 kDa was obtained with only MT₁ antibody in smooth muscle cells, whereas a protein bands corresponding to 40 kDa were obtained with MT₁ and MT₂ antibody in the brain.