Related Experiment Videos
Enkephalin mydriasis in mice
Abstract:
Morphine is known to produce mydriasis in mice. We have found that enkephalins caused a similar effect. Morphine was twice as active as D-Ala-D-Leu-enkephalin (BW-180C), 5 times as active as Met-enkephalin and 7 times as active as Leu-enkephalin. The time course of the effect was shortest for the enkephalins ( t 1/2 = 8-12 min), intermediate for BW-180C (60 min) and longest for morphine (80 min). Naloxone antagonised the effect of all agents to a similar extent. The question whether enkephalins are involved in the physiological regulation of pupillary diameter was investigated by administering either naloxone or D-phenylalanine to mice. None of these agents changed pupillary size, thus making such an involvement unlikely.
Insights
Enkephalins, similar to morphine, cause mydriasis (pupil dilation) in mice. However, enkephalins are not involved in the natural regulation of pupillary diameter.
Area of Science:
- Pharmacology
- Neuroscience
- Ophthalmology
Background:
- Morphine is a known mydriatic agent in mice.
- Enkephalins are endogenous opioid peptides with various physiological roles.
Purpose of the Study:
- To compare the mydriatic potency and time course of enkephalins versus morphine.
- To investigate the potential physiological role of enkephalins in pupillary diameter regulation.
Main Methods:
- Administered morphine, D-Ala-D-Leu-enkephalin, Met-enkephalin, and Leu-enkephalin to mice to assess mydriasis.
- Compared the potency and duration of mydriatic effects.
- Administered naloxone or D-phenylalanine to mice to evaluate the involvement of enkephalins in physiological pupillary control.
Main Results:
- Enkephalins induced mydriasis in mice, with varying potencies relative to morphine.
- The duration of mydriasis was shortest for enkephalins and longest for morphine.
- Naloxone antagonized the mydriatic effects of all tested agents similarly.
- Administration of naloxone or D-phenylalanine did not alter basal pupillary diameter in mice.
Conclusions:
- Enkephalins possess mydriatic properties in mice.
- The findings suggest that enkephalins are unlikely to be involved in the physiological regulation of pupillary diameter.