Respiratory responses to somatostatin microinjections into the Botzinger complex and the pre-Botzinger complex of the rabbit

The respiratory responses to bilateral microinjections (30-50 nl) of 5 mM somatostatin (SOM) or 10 mM cyclosomatostatin (c-SOM, a SOM antagonist) into the Botzinger complex (BotC), the pre-Botzinger complex (preBotC) 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 BotC decreased respiratory frequency and the rate of rise of phrenic nerve activity without obvious changes in its peak amplitude. SOM microinjected into the preBotC 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 preBotC 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 preBotC contributes to shape the pattern of baseline respiratory activity and that SOM receptors within the BotC and the preBotC have a role in the modulation of respiration in the rabbit. (C) 2011 Elsevier Ireland Ltd. All rights reserved.