Figure 2. Selective activation of G_q proteins by melatonin.

Membranes were isolated from dispersed gastric muscle cells and incubated with [³⁵S]GTPγS for 20 min in the presence or absence of melatonin (1 μM). Aliquots were added to wells coated with antibody to Gα_i2, Gα_i3, Gα_s, or Gα_q for 2 h and bound radioactivity from each well was counted by liquid scintillation. The amount of [³⁵S]GTPγS bound to the activated Gα subunit was expressed as counts per minute (cpm) per milligram of protein. Melatonin induced significant increase in the binding of [³⁵S]GTPγS.Gα complexes to wells coated with Gα_q antibody only. Values are mean±SEM of 4 experiments. **p<0.001 significant increase in Gα_q-[³⁵S]GTPγS binding in respone to melatonin.