CHRONIC THC EXPOSURE IN ADOLESCENT VERVET MONKEYS: EFFECTS ON RETINAL FUNCTION

Acute and chronic cannabis/Δ9-tetrahydrocannabinol (THC) use has been shown to alter retinal responses in adults. However, the longitudinal impact of chronic THC exposure during adolescence on retinal function, as well as the reversibility of these effects following cessation, remains poorly characterized.
In this study, we investigated the evolution of retinal neuronal activity in a cohort of 24 adolescent vervet monkeys administered THC (2mg/kg, p.o.) daily for three months. Full-field electroretinograms (ERGs) were recorded using a handheld device (RETeval, LKC Technologies), in accordance with the International Society for Clinical Electrophysiology of Vision standards. Recordings were obtained at three experimental timepoints: at baseline (N=8); shortly after the end of the treatment period (24-48h after the last THC dose; N=24); and three months following treatment cessation (N=16).
Comparisons between baseline and post-treatment data show significantly increased amplitudes and delayed responses under both photopic and scotopic conditions. Preliminary analysis of the last recordings indicates that most alterations were reversible after three months of abstinence, except for the increased latencies of the photopic b-waves and the increased amplitudes of the scotopic a-waves.
These findings demonstrate persistent modifications of retinal synaptic transmission following chronic THC exposure during adolescence and underline the utility of the ERG as a non-invasive tool to quickly detect cannabinoid-induced neuronal dysfunction, with potential brain-wide implications. As a growing number of countries legalize cannabis, further research is warranted to elucidate the risks of cannabis use among youth and to inform targeted public health interventions.