Figure 6. Comparison of nerve-induced contractile responses in the WT and W/W^v mouse IAS in the absence of atropine.

(A) Sample traces showing the effects of MRS2500 and L-NNA on contractile responses elicited with 5 Hz EFS (10 s) in WT (Aa) and W/W^v (Ab) mice in the absence of atropine. Under control conditions EFS gave rise to relaxation (1^st traces). MRS2500 did not significantly reduce nerve evoked relaxation in WT mice but it did in W/W^v mice (2^nd traces). Following combined L-NNA and MRS2500 addition a large contractile response was seen in both animals (3^rd traces). These contractions were abolished by atropine (1 μM; 4^th traces). (B) Summary graph of the effects of blockers on nerve-induced changes in contractile activity during the initial 10s and the subsequent 50s of EFS in WT (Ba) and W/W^v (Bb) mice. Contractile area during EFS (5 Hz, 60s) is compared to the contractile area preceding EFS (“Pre-stim”, n=10 WT; n=6 W/W^v). All areas are normalized to area/10s. EFS gave rise to significant (*) relaxation in both WT and W/W^v mice (black bars, n=4 WT; n=6 W/W^v)). In the presence of MRS2500 (dark grey bars, n=4 WT; n=6 W/W^v) relaxation in WT mice was unchanged whereas it was significantly (&) reduced during both time periods of EFS in W/W^v mice. Combined addition of MRS2500 plus L-NNA (light grey bars, n=10 WT; n=6 W/W^v) resulted in significant (*) contraction in both animals during both time periods of EFS. Contractions were abolished by atropine (white bars, n=10 WT; n= 6 W/W^v) and a significant (*) relaxation was revealed during the latter 50s time period in both animals. Shown are mean values ±S.E.M.