Fig. 4.
Intracellular injection of anti-GαoFab fragments inhibits slow responses to 5-HT. A,i, In the absence of tropisetron, 5-HT evokes a biphasic response (control), consisting of a fast 5-HT3-mediated depolarization, followed by the 5-HT1P-mediated slow depolarization. The injection of anti-Gαo Fab fragments antagonizes the slow but not the fast response to 5-HT. ii, Control responses of the same neuron to 5-HT and histamine are shown. The control response to 5-HT is again biphasic; the fast response is very small. An action potential is seen during the depolarization. Injection of anti-Gαo Fab fragments inhibits the slow response to 5-HT far more than that to histamine. The mean ratio of the amplitude of slow responses to histamine after injection of anti-Gαo Fab fragments to control responses obtained in the same cells (1.3 ± 0.1) was not significantly different from 1 (n = 6;p = 0.0804). B, The effects of intracellular injection of anti-Gαo Fab fragments on fast and slow responses of AH/type 2 neurons to 5-HT are compared.