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Serotonergic modulation of eye blinks in cat and monkey
M S LeDoux1, J F Lorden, J M Smith
1Department of Neurology, University of Tennessee College of Medicine, Memphis 38163, USA. mledoux@utmem1.edu
Neuroscience Letters
|October 1, 1998
Summary
Serotonin influences blinking. Blocking serotonin receptors (5-HT2) altered blink reflexes in cats and monkeys, suggesting a role in blepharospasm.
Area of Science:
- Neuroscience
- Pharmacology
- Ophthalmology
Background:
- The blink reflex is crucial for ocular protection.
- Serotonin's role in facial motor control is not fully understood.
Purpose of the Study:
- To investigate the role of serotonin in modulating spontaneous and reflexive blinking.
- To explore the effects of serotonin receptor 5-HT2 modulation on blink parameters.
Main Methods:
- Administered serotonin and the 5-HT2 antagonist ketanserin via facial nucleus injections in cats.
- Utilized the 5-HT2 agonist 2,5-dimethoxy-4-iodoamphetamine and ketanserin in a monkey model.
- Measured blink reflex components (R1, R2), spontaneous blink frequency, duration, amplitude, and velocity.
Main Results:
- In cats, ketanserin increased blink reflex latency; serotonin and ketanserin affected R2 duration and amplitude.
- Serotonin induced blepharospasm and hemifacial spasm in cats.
- In monkeys, a 5-HT2 agonist increased spontaneous blink frequency, while ketanserin decreased blink velocity and frequency.
Conclusions:
- Serotonergic innervation of the facial nucleus plays a significant role in modulating spontaneous and reflexive blinks.
- Dysfunction in serotonergic systems may contribute to the pathophysiology of certain blepharospasm cases.