Gender tearing distinctions

A study published in Investigative Ophthalmology & Visual Science has revealed the intricate role of cannabinoid CB1 receptors in regulating circadian tearing in mice, with notable differences observed between males and females. The research, conducted at Indiana University, offers new insights into how cannabinoid signaling influences tear production, and sheds light on potential implications for ocular health.

The study found that, though both male and female mice exhibit circadian cycles of basal tearing, males demonstrated a robust fluctuation, with peak tearing occurring during the active phase, while females displayed a dampened amplitude in tearing variations, peaking later than males. Interestingly, CB1 receptor activation in females suppressed tearing during the rest phase, while antagonism of the receptor enhanced tear production, effectively increasing the amplitude of circadian oscillations in the mice.

The researchers also discovered that female mice experience tonic inhibition of tearing via CB1 receptors during the rest phase. This sex-specific regulation was further supported by immunohistochemical analysis, which revealed CB1 receptor expression in both parasympathetic inputs and myoepithelial cells of female lacrimal glands – a feature not observed in the male mice.

The findings highlight the complexity of cannabinoid signaling in ocular physiology and suggest that CB1 receptors play a key role in maintaining circadian homeostasis in tearing. These male/female differences in regulation could have implications for understanding gender-specific vulnerabilities in conditions like dry eye disease (DED), as well as paving the way for future research exploring cannabinoid-based therapies for managing tear production and ocular surface health.