Reduced pupillary sensitivity to topical phenylephrine associated with the relaxation response

Area of Science:

• Physiology
• Pharmacology
• Mind-Body Medicine

Background:

• The pupillary response to phenylephrine, an alpha-adrenergic agonist, reflects the sensitivity of ocular alpha-end-organs.
• The relaxation response is a physiological state of decreased sympathetic nervous system activity.
• Investigating the impact of regular relaxation response practice on autonomic nervous system end-organ sensitivity is of clinical interest.

Purpose of the Study:

• To determine if regular elicitation of the relaxation response alters human alpha-end-organ responsivity.
• To quantify changes in pupillary dilatation following phenylephrine instillation after a period of relaxation response training.

Main Methods:

• A prospective, randomized, controlled study was conducted.
• Participants underwent baseline pupillometry and phenylephrine challenge.
• Experimental group practiced daily relaxation response; control group sat quietly for 4-6 weeks.
• Post-intervention pupillometry and phenylephrine challenge were repeated for comparison.

Main Results:

• Pupillary dilatation in the experimental group was significantly diminished compared to the control group (p < .02).
• This indicates reduced pupillary response to the alpha-adrenergic agent phenylephrine.

Conclusions:

• Regular elicitation of the relaxation response is associated with diminished alpha-end-organ responsivity.
• Findings suggest a potential mechanism for altered autonomic nervous system regulation through mind-body interventions.
• This may have implications for understanding physiological adaptations to stress reduction techniques.