Modulation of separation distress by alpha-MSH.

Area of Science:

• Neuroendocrinology
• Animal Behavior
• Developmental Neuroscience

Background:

• Separation-induced distress vocalizations (DVs) are a key indicator of distress in altricial birds.
• Alpha-melanocyte-stimulating hormone (alpha-MSH) is a peptide hormone with diverse physiological roles, including in camouflage and stress responses.

Purpose of the Study:

• To investigate the effects of centrally administered alpha-MSH on distress vocalizations and squatting behavior in domestic chicks.
• To examine dose-response, time course, and interactions with opioid systems and social stimuli.

Main Methods:

• Domestic chicks were administered varying doses of alpha-MSH centrally.
• Distress vocalizations and squatting were recorded in the presence and absence of social stimuli (mirrors, conspecific).
• Interactions with peripheral naloxone and central/peripheral morphine were assessed.

Main Results:

• Alpha-MSH (≥0.04 µg) eliminated the suppressive effects of social stimuli on DVs.
• An initial 10-15 minute effect was followed by an hour of inhibited DVs and dose-dependent vigilant squatting.
• No tolerance developed over six days; no interaction with naloxone or morphine was observed.

Conclusions:

• Centrally administered alpha-MSH modulates distress vocalizations and induces a vigilant posture in chicks.
• These effects suggest alpha-MSH may activate a central fear-like state to adaptively manage distress and defensive behaviors.
• Alpha-MSH's role in chicks may parallel its function in amphibian defensive camouflage.