Figure 2. Effects of ₁-adrenoceptor subtype selective agonists and antagonist on [Ca²⁺]_i in human submandibular gland cells. (A,C,E) Fluorescence image of fluo-3AM-loaded cells before treatment with phenylephrine, A61603, or 5-methylurapidil. No change in [Ca²⁺]_i fluorescence intensity (FI) was observed after pre-treatment with 5-methylurapidil (E). There were no marked differences in FI among A, C, and E. The maximum of FI was observed at about 1500 sec after agonist treatment. (B,D) A significant increase in [Ca²⁺]_i FI at the individual cell level after treatment with phenylephrine (1 µM) or A61603 (100 µM), respectively. (F) A mild increase in [Ca²⁺]_i FI at the individual cell level with 1 µM of phenylephrine after pre-treatment with 5-methylurapidil (0.1 µM). (G) The dynamics of FI at the individual cell level treated with phenylephrine, A61603, or 5-methylurapidil plus phenylephrine in the human submandibular gland cells. (H) Fluorescence image of fluo-3AM-loaded cells with KCl stimulation (50 mM).