Bisphenol A exposure inhibits contrast sensitivity in cats involving increased response noise and inhibitory synaptic transmission

Contrast sensitivity (CS) is one of the primary fundamental factors determining how well we can see, and it directly influences object recognition. Whether bisphenol-A (BPA, an environmental xenoestrogen) can perturb contrast detection in the visual system has yet to be elucidated. In the present study, we analyzed CS of single neurons in the primary visual cortex (area 17, A17) of cats before and after BPA exposure using a multiple-channel recording technique. The results showed that CS of A17 neurons was markedly depressed with an increased contrast threshold after two hour of intravenous BPA administration, which had a positive correlation with decreased firing rates of A17 neurons. Additionally, responses of these neurons presented an overt increase in the trial-to-trail response variability (a kind of neuronal noise), which could disturb the information-filtering function of single neurons. We also found that neuronal CS in the visual relay station was not disturbed after BPA administration, which rules out the contribution of CS alteration in the optical pathway. Importantly, acute BPA treatment obviously increased the inhibitory innervation to the visual pyramidal neurons. This implies that alteration of intracortical inhibitory regulation contributes to the compromised contrast detection in the visual system after BPA treatment.