Melatonin modulation of vocal output elicited from separate midbrain sites

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: MON 142-166-Hypothalamus-Pituitary Development & Biology
Basic/Clinical
Monday, June 17, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board MON-156
Ni Feng*1 and Andrew Bass2
1Cornell University, Ithaca, NY, 2Cornell Univ, Ithaca, NY
Conserved features of vertebrate acoustic communication include context-dependent vocalizations, occurrence over predictable daily and seasonal cycles, and the ability of neuromodulators to pattern motor output by acting upon dedicated neural networks. Most studies on fish circadian rhythms have investigated the effects of photoperiod and melatonin, the time-keeping pineal hormone, on locomotion and feeding, with little attention paid to melatonin’s action on other behaviors such as vocalization (1). We used a highly vocal fish, the plainfin midshipman (Porichthys notatus), to investigate melatonin influence on the excitability of a vocal network (VN) dedicated to sound production. VN output directly patterns the activity of a readily recorded vocal nerve volley (“fictive call”) that directly determines the temporal attributes of natural calls (2). Male midshipman produce several call types distinguishable mainly by duration, the longest of which is the courtship “hum” produced only at night during the summer breeding season (3). Given the ability of constant light to abolish and constant dark to increase baseline melatonin production (e.g. 4), we tested the hypothesis that the known stimulatory effects of night and constant darkness on midshipman vocal excitability (5) depend on increased melatonin action. Five days of melatonin implant increased the duration of fictive calls in fish held under constant light, while daily administration of a melatonin receptor antagonist decreased call duration in fish held under constant darkness. Furthermore, melatonin’s potentiating action on fictive call duration was greatest upon activation of a lateral midbrain vocal-active site, which produces longer fictive calls reminiscent of natural hums. In contrast, shorter fictive calls reminiscent of natural agonistic “grunts” were reliably elicited from a medial site and were less sensitive to melatonin action. These results suggest that subdivisions within the midshipman VN encode distinct, social context-dependent vocalizations and exhibit differential sensitivity to neuroendocrine regulation. Given the expression of melatonin receptors in fish brain and in specific song nuclei of songbirds (1,6), evidence for site-specific encoding of different call types in mammalian midbrain (7,8), and the widespread occurrence of daily and seasonal cycles in vocal behaviors in vertebrates, we propose our results are widely applicable between vocal fishes and tetrapods.

(1) Falcón J. et al., Gen Comp Endocrinol 2009; 469:482. (2) Chagnaud BP et al., Nat Commun 2011; 2:346. (3) Brantley RK, Bass AH, Ethology 1994; 213:232. (4) Bayarri MJ et al., J Pineal Res 2002; 34:40. (5) Rubow TK, Bass AH, J Exp Biol 2009; 3252:3262. (6) Gahr M, Kosar E, J Comp Neurol, 1996; 308:318. (7) Bandler R, Carrive P, Brain Res 1988; 95:106. (8) Fenzl T, Schuller G, J Neurosci 2002; 1974:1986.

Nothing to Disclose: NF, AB

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: NSF IOS 1120925; Sigma Xi Cornell Chapter; Student research grant in animal behavior