Buccal rhythm generation in metamorphic bullfrogs is dependent on glycine

Fish and early developmental amphibians use gill structures to exchange gases in water. In jawless fish, the neural circuit responsible for generating gill ventilation (buccal) rhythm is adjacent to the trigeminal nerve (CN V). In amphibians, a homologous rhythm generating site has been identified just caudal to the vagus nerve (CN X). The amphibian buccal oscillator is reported to be driven by Cl− mediated mechanisms, and subsequent inhibition of either GABA or glycinergic receptors abolishes this rhythm. This study investigates the effects of Cl− mediated antagonism of buccal rhythm generation and the distribution of buccal rhythm generating circuits. We isolated brainstems from bullfrog tadpoles, placed them in a recording chamber, and allowed them to recover for 1 hour perfused with artificial cerebral spinal fluid (aCSF) equilibrated with 98.5% O2 and 1.5% CO2 (pH 7.8). During this time, neural activity from the facial (CN VII) and hypoglossal (CN XII) cranial nerves was recorded. Following recovery,...