European journal of pharmacology
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Pupillary response of albino rabbits were recorded using an infrared video pupillometer. The transient response to an i.v. injection of morphine (1-12 mg/kg) consists of three phases. Phase 1 is a brief mydriasis of 20 s duration. ⋯ Thus, dynamic pupillography reveals that the terms "miosis' and "mydriasis' may be insufficient to fully describe opiate-induced pupillary effects. All three phases are blocked by naloxone (0.1 mg/kg i.v.) and by topical pretreatment with scopolamine. These results are consistent with the theory that morphine alters pupil size by interaction with opiate receptors that are involved in the control of parasympathetic output to the iris.