Figure 2.
Effects of increasing the levels of endogenously released GABA in P1 brainstem–spinal cord (SC) and medullary slice preparations by bath application of the uptake inhibitor nipecotic acid (Nip). A, Representative recordings from brainstem–spinal cord (left column) and medullary slice (right column) preparations. Nipecotic acid caused a clear decrease in respiratory frequency in the brainstem–spinal cord preparation with 20 min of application. A part of the inhibition was removed in the presence of the GABAB receptor antagonist saclofen (Sac). The remainder of the inhibition was removed by the addition of the GABAA receptor antagonist bicuculline (Bic). In medullary slice preparations, there was no significant change in respiratory frequency in response to application of nipecotic acid. However, there was a significant increase in respiratory frequency by the subsequent application of saclofen. The increase in respiratory frequency was blocked by bicuculline, demonstrating that the major component of the excitatory action was via GABAA receptors. B, Population data from bath application of drugs in brainstem–spinal cord and medullary slice preparations. *p < 0.05, significant difference relative to control. Brainstem–spinal cord and medullary slice preparations were bathed in 3 and 9 mm [K+]o, respectively.