Fig. 3.

Respiratory-related firing is preserved in overwintered frogs despite hypoxia exposure. Firing of motoneurons receiving respiratory-related synaptic input (RRSI) from the rhythm generator regions (A) was recorded in controls (n=8, B) and overwintered frogs (n=6, F). B Representative recording of a control neuron firing in response to RRSI in baseline conditions (BL), when affected by hypoxia (Hx- 7min) and after network failure (Hx- after network failure), where both tonic firing and silence could be observed. Controls firing in baseline conditions was compared to the last measurements before network failure (C–E). Hypoxia exposure decreased control’s firing frequency (C) and number of spikes (D) triggered by the RRSI, with no change to the action potential (AP) threshold (E). F Representative recording of an overwintered motoneuron firing in baseline conditions (BL) followed by the same time that hypoxia affected firing in controls (Hx- 7min) and after 40 min in hypoxia (Hx- 40 min). Overwintering prevented the hypoxia effect on RRSI-triggered firing frequency (G) and number of spikes (H), as well as decreased AP threshold (I). Results were compared using paired t-tests, and a p < 0.05 was considered statistically significant (∗)