Respiratory Reactions to Microinjection of GABA and Baclofen into the Betzinger and Pre-Betzinger Complexes in Rats

Abstract

Acute experiments on anesthetized rats were performed to study changes in the pattern of respiration after microinjections of GABA (10–5 M) and baclofen (10–6 M) solutions into the Betzinger (BC) and pre-Betzinger (PBC) complexes. Acting at the level of the BC, GABA was found to decrease inspiration time and increase expiration time, producing a slight reduction in respiratory rate; respiratory volume and pulmonary ventilation increased. Injections of GABA into the PBC had marked inhibitory effects on the respiratory rhythm, with prolongation of inspiration and expiration and a decrease in respiratory volume. Injection of the specific GABAB receptor agonist baclofen into the BC decreased the duration inspiration and respiratory volume but increased respiratory frequency, while injection of baclofen into the PBC had essentially no effect on the duration of inspiration or respiratory frequency, while volume parameters increased. These reactions provide evidence of different contributions of GABAergic mechanisms, including GABAB receptors, in the BC and PBC to controlling the rhythm and volume parameters of respiration.