Beating intraocular hearts: light-controlled rate by autonomic innervation from host iris

Area of Science:

• Autonomic Nervous System
• Cardiovascular Physiology
• Ocular Innervation

Background:

• The sympathetic ground plexus in the rat iris can innervate transplanted tissues.
• Embryonic hearts can be successfully transplanted into the anterior eye chamber.

Purpose of the Study:

• To investigate the functional autonomic innervation of embryonic heart transplants in the rat anterior eye chamber.
• To assess the heart transplant's response to autonomic stimuli modulated by light.

Main Methods:

• Transplantation of embryonic hearts into the anterior eye chamber of rats.
• Monitoring heart transplant rate and pupil diameter in response to light.
• Pharmacological interventions including topical atropine, sympathetic decentralization, and propranolol administration.
• Administration of isoprenaline to assess adrenergic receptor function.

Main Results:

• Transplanted hearts beat continuously for at least five months, with rates increasing over time.
• Increased light caused deceleration, and decreased light caused acceleration of transplant heart rate, correlating with pupil diameter changes.
• Atropine reduced light-dependent rate variations. Waking stress increased heart rate, an effect reduced by decentralization and abolished by propranolol.
• Decentralization decreased the high rate observed in red light, an effect reversed by isoprenaline.

Conclusions:

• The intraocular heart transplant receives dual functional autonomic input from the host iris.
• The transplanted heart serves as a sensitive monitor of autonomic nervous activity.
• Autonomic activity can be physiologically modulated by altering light influx to the eye.