PLA-located blockade of PAG-induced echolocation calls and communication calls. The percentage of successful stimulations (y-axis) for eliciting vocalizations in the PAG is represented during and after KA induced blockade of PLA. Echolocation calls are graphed with diamonds, while squares are used for communication calls. The kynurenic acid application is indicated by black horizontal bars below the x-axis. Onset and termination times of iontophoresis are given in italics. Onset and termination times of iontophoresis are indicated by numbers at both ends of the bars in italics. Stimulation success (%) was calculated for intervals of 2 s. Black arrows on the abscissa indicate the 25% blockade boundary. (A) Application of KA to the left PLA. The ipsilateral production of PAG-induced echolocation calls (left electrode) cannot be blocked, although a slight depression can be noticed in the first half of the graph. The contralateral production of PAG-induced communication calls (right electrode) is only rarely influenced by the glutamate antagonist KA. (B) A blockade of the right PLA totally blocks the production of contralaterally PAG-induced echolocation calls (left electrode), while the ipsilateral production of communication calls (right electrode) again is barely influenced. Note that the curve for PAG ipsilateral (communication call) starts around 50%. (C) Bilateral blockade of both PLA sites again leads to a total depression of PAG-induced echolocation calls, while PAG-induced communication calls can be elicited across the entire experimental run. Prior to each experiment, vocal answers were stable for at least 10 minutes at a value comparable to the data shown at the start of the application of the antagonist.