Fig. 9.

Enhancement of CO₂ sensitivity by synapse transmission. A. With intact synaptic transmission, the post-synaptic neurons had a C value significantly higher than the presynaptic units (P=9.0E-06, n=61). B. Such a difference was abolished by a blockade of excitatory synaptic transmission with 10µM CNQX (P=0.45, n=13). C. In the presence of 10µM CNQX, some units lost the CO₂ chemosensitivity almost completely (P=7.0E-05, n=20). D. Similar effect was seen with a non-specific blockade of synaptic transmission using low Ca²⁺ (<1 µM) and high concentrations of Mg²⁺ (2 mM) (P=3.3E-06, n=13). E. Both reference and target units showed identical CO₂ sensitivity when they were grouped randomly (P=0.45, n=4). F. However, one of the units in each pair showed much higher CO₂ sensitivity than the other when they were pooled together (P=0.0004, n=4). Data are represented as mean ± S.D.