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Updated: Aug 9, 2026

Methods to Quantify Pharmacologically Induced Alterations in Motor Function in Human Incomplete SCI
Published on: April 18, 2011
Possible serotonergic mediation of tonic immobility: effects of morphine and serotonin blockade
Abstract:
Small doses of morphine, within the range of 0.02 mg/kg to 10.15 mg/kg were administered to chickens (Gallus gallus) and the effect on the fear-based tonic immobility (TI) response determined. All doses at and above 0.13 mg/kg enhanced the TI response significantly above the levels produced for the 0.2 mg/kg dose and the distilled water control group. Administration of a single large dose of p-chlorophenylalanine prevented the morphine-induced enhancement of TI. It was suggested that serotonin systems mediate morphine effects on tonic immobility in chickens.
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