A, SP (1 μm) application elicits an increase in frequency verifying correct placement of drug pipette within the rhythmogenic preBötC. B, group data showing the peak increase in XII nerve burst frequency evoked by local application of SP into the preBötC (n = 4). C, local application of UBP-302 (100 μm) from the same drug pipette into the same site that SP was injected in A had no effect on frequency. D, group data showing the average burst frequency during control and the minimum frequency observed in the 60 s following local injection of UBP-302. Asterisk indicates significance, *P < 0.05.