PLA-located blockade of PAG-induced echolocation calls. At both electrodes, echolocation calls were triggered. Refer to Fig. 2 for explanations on graph. (A) Application of kynurenic acid to the left PLA does not influence the elicitability of ipsilaterally PAG-induced echolocation calls (left electrode), whereas it lowers dramatically the efficiency of contralaterally induced echolocation calls (right electrode). The elicitability does not recover to the 75% mark within termination of the experiment at minute 120. (B) A blockade of the right PLA totally blocks the production of contralaterally PAG-induced echolocation calls (left electrode), while ipsilateral-induced echolocation calls (right electrode) are little affected (although some drop in elicitability can be detected). Prior to each experiment, vocal answers had to be stable for at least 10 min at a value comparable to the data shown at the application of the antagonist.