Mario Penna

Hormone-induced vocal behavior and midbrain auditory sensitivity in the green treefrog, Hyla cinerea

SummaryTwenty four castrated male, 6 intact male, and 11 intact female Hyla cinerea were injected subcutaneously with 25 μg arginine-vasotocin (AVT) and induced to call 1 h later in response to the playback of a conspecific mating call. Eighteen castrated males and 8 intact females were implanted 5 mg androgen pellets for 3 weeks prior to the neuropeptide injection. Among castrated males, 6/9 testosterone (T) implanted, 4/9 dihydrotestosterone (DHT) implanted and 2/6 non implanted individuals produced calls after being administered AVT. 5/6 intact non implanted males and 6/8 T intact implanted females also called, and 3 intact non implanted females remained silent after the injection. Evoked calls had a mid-frequency spectral peak at about 1900 Hz which is absent in field-recorded mating calls of this species. Calls of implanted females and castrated non implanted males were shorter than those of castrated implanted and intact non implanted males. Audiograms measured before hormone implants showed dips of enhanced sensitivity at about 0.5, 0.9 and 3.0 kHz in males and females. After AVT injection, thresholds at frequencies within the 0.7–1.5 kHz range were increased in castrated males. Such reduction in sensitivity points to an inhibition of the auditory system during hormone induced vocal activation.

Effects of rhythm and rate changes on inotropic action of ouabain.

Summary In failing cardiac muscle, postextrasystolic potentiation decreases at a slower rate than response in a series at a regular frequency. Postextrasystolic contraction is not improved by ouabain. The latent period of ouabain action is related to elapsed time, not the total number of contractions.