On-column injections were made using a septum-equipped temperature programmable injector (SPI) fitted with a high performance insert directly connected to a DB-5 HT capillary column (15 m × 0.25 mm i.d., 0.1 μm film thickness; J&W Scientific) with helium as carrier gas at a head pressure of 3 psi.
On the next day, the cannula was connected to a P23 Db pressure transducer (Statham Gould) coupled to a pre-amplifier (model ETH-200 Bridge Bio Amplifier, CB Sciences) connected to a Powerlab computer recording system (Powerlab 8SP, ADInstruments) to record MAP and HR.
The previously implanted catheter was connected to a Statham (P23 Db) pressure transducer (Statham-Gould, Valley View, OH) coupled to a multi channel recorded (PowerLab Multirecord).
The catheter was connected to a Statham (P23 Db) pressure transducer (Statham-Gould, Valley View, OH) coupled to a multichannel recorder (PowerLab Multirecord, USA), permitting the acquisition of cardiovascular data by computer.
The recording setup consisted of an omnidirectional Sennheiser K6 microphone (frequency response: 30 to 20000 Hz±1 dB) connected to a Marantz PMD 671 digital recorder with sampling frequency at 48 kHz.
Playback stimuli were presented with speakers (Ion Block Rocker, Ion Audio, LLC. US, www.ionaudio.com; 70 Hz–50 kHz ± 3 dB) connected to a MacBook Pro using Quick Time Player Pro (V:7.6.9).
Stimuli were presented via speakers (Ion Block Rocker; frequency response 70 Hz–50 kHz ± 3 dB) connected to a MacBook Pro using QuickTime Player Pro (v7.6.9).
The hydrophones had a flat (±2 dB) frequency response between 100 160 kHz and were connected to a 48 channel conditioning box with 40 dB gain and a fourth order bandpass filter with −3 dB frequencies at 2 kHz and 200 kHz.
Pup vocalisations were recorded using a BeyerDynamic M69TG (frequency response 50 Hz–16 kHz±2.5 dB, BeyerDynamic, Heilbronn, Germany) connected to a Marantz PMD 660 digital recorder (frequency response 16 kHz (−0.5 dB), dynamic range 80 dB).
The electrodes had magnification of 20 times, impedance of 10 GΩ and rejection of 92 dB, and were connected to a computerized device of electromyography (DataHominis Tecnologia Ltda), with a magnification of 100 times (2000 amplification of total time), a pass filter of 15 Hz to 1 kHz and an acquisition frequency of 2000 Hz.
All playbacks were broadcast using an iPod Nano (fifth generation) connected to a speaker amplifier (ION Block Rocker, 70 Hz–50 kHz ±3 dB).
