The respiratory responses to bilateral microinjections (30-50 nl) of 5mM somatostatin (SOM) or 10mM cyclosomatostatin (c-SOM, a SOM antagonist) into the Bötzinger complex (BötC), the pre-Bötzinger complex (preBötC) and the rostral inspiratory portion of the ventral respiratory group (iVRG) were investigated in urethane-chloralose anesthetized, vagotomized, paralysed and artificially ventilated rabbits. SOM microinjections into the BötC decreased respiratory frequency and the rate of rise of phrenic nerve activity without obvious changes in its peak amplitude. SOM microinjected into the preBötC caused increases in respiratory frequency and decreases in peak phrenic activity associated with increases in its rate of rise. No changes in respiration were induced by SOM microinjections into the iVRG. Microinjections of c-SOM into the preBötC caused decreases in respiratory frequency as well as in peak amplitude and rate of rise of phrenic nerve activity. The results show that endogenously released SOM within the preBötC contributes to shape the pattern of baseline respiratory activity and that SOM receptors within the BötC and the preBötC have a role in the modulation of respiration in the rabbit.
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