VENTILATORY EFFECTS OF GABA DURING DEVELOPMENT IN RABBITS. † 2036

Abstract

A possible role of gamma amino butyric acid (GABA) in SIDS is based on data obtained in anesthetized animals. Therefore, we evaluated effects of increased levels of GABA on minute ventilation (VE) in 27 awake 1-3 days old (L grp) and 10-14 days old (LL grp) rabbits using a flow plethysmograph and the barometric method to measure VE in L and LL grps, respectively. Sham rabbits (LS and LLS grps) were injected (i.p.) with saline (S). GABA levels were increased by i.p. injection of 20 mg/kg of aminooxyacetic acid (AOAA), an inhibitor of GABA transferase, in grps LA and LLA. 45 min after AOAA, animals were injected with 100 mg/kg of 3-mercaptopropionic acid to block post mortem synthesis of GABA and 2 min later were sacrificed by decapitation. The brain was removed on dry ice, brain stem, cerebellum and cerebrum were dissected and stored at -80°C. GABA levels were measured using capillary electrophoresis. Values are presented in μg/g wt tissue±SE. Brain stem GABA levels were higher in LA and LLA than in LS and LLS, respectively. However, VE was similar in all rabbits. Lack of the expected depression of VE with increased GABA levels may be due to immaturity of several components of the GABA-ergic mechanisms, e.g. GABA receptors, and/or sparsity of neuronal connections between respiratory and GABA-ergic neurons during the early postnatal period in rabbits. Thus, high levels of GABA may not influence development of SIDS. Table