Figure 6. Effects of transmural nerve stimulation on PGF_2α- and NAd-induced excitations.

In a CCSM preparation, PGF_2α (0.1 μm) initiated sustained contraction (Aa) and an associated increase in [Ca²⁺]_i (Ab). In the presence of PGF_2α (0.1 μm), brief transmural stimulation initiated phasic relaxation (Aa) and reduced [Ca²⁺]_i by about 30% (Ab). Prolonged stimulation inhibited PGF_2α-induced contraction by about 90% (Aa) and reduced [Ca²⁺]_i by about 50% (Ab). In the same preparations, NAd (0.3 μm) caused sustained contraction (Ba) and a corresponding increase in [Ca²⁺]_i (Bb). Brief transmural stimulations initiated phasic relaxations (Ba) and reduced [Ca²⁺]_i by about 20% (Bb). Prolonged stimulation inhibited the contraction by about 90% (Ba) and reduced [Ca²⁺]_i by about 50% (Bb). These results are summarized in C and D where open circles (○) indicate changes in [Ca²⁺]_i and filled circles (•) indicate changes in tension. The scale bar on the right of Ba applies to both tension traces and the scale bar on the right of Bb refers to both Ca²⁺ traces.