Physiological contribution of P2X receptors in postreceptoral signal processing in the mouse retina.

ATP activates P2X receptors and acts as a neurotransmitter in the nervous system. We have previously reported that P2X receptors modulate the firing rate of retinal ganglion cells. Since many subtypes of P2X receptors are distributed in the mouse retina, it is likely that the modulatory effects of P2X receptor-mediated signaling can occur at multiple synaptic levels in the retina. In this study, we investigated whether P2X receptors expressed between the photoreceptor layer and the inner nuclear layer in the mouse retina were physiologically functional, by electroretinography (ERG). In the combined rod-cone ERG and the scotopic ERG, intravitreal injection of PPADS, an antagonist of P2X receptors, had no effects on the amplitude of the a-wave, but decreased the amplitude of the b-wave. In the photopic ERG, intravitreal injection of PPADS significantly decreased the amplitude of both the a-wave and the b-wave. In ex vivo recordings, a decrease in the b-wave amplitude was observed at 20µM PPADS, confirming that the inhibition of the b-wave by intravitreal injection of PPADS is due to the inhibition of P2X receptors. Our findings suggest that P2X receptor-mediated signaling has a physiological effect in both the rod and the cone pathways in postreceptoral processing.

Symptoms of Dry Eye Disease and Personality Traits.

The essential targets of dry eye disease (DED) treatments include both objective signs and subjective symptoms. However, due to the numerous subjective symptoms, it is understandable why little association has been found between the signs and symptoms. Although psychological influences on the subjective symptoms have been reported, little is known about the influence of personality traits. The present study analyzed the relationship between the signs/symptoms of DED and the personality traits of patients using a cross-sectional design. We examined 56 DED patients (mean age; 62.4 ± 12.9, range 34-85 years) visiting the outpatient clinic of the Department of Ophthalmology at the Nippon Medical School Hospital in Tokyo, Japan. Objective signs evaluated included the Schirmer I test, tear breakup time (BUT), fluorescein and lissamine green staining, and tear osmolality. Subjective symptoms were assessed by the Ocular Surface Disease Index (OSDI) and Dry Eye-Related Quality-of-Life Score (DEQS) questionnaires. For personality traits, the Big Five personality traits model analysis was used. Correlations between the objective signs, subjective symptoms, and personality traits were analyzed. A significant correlation was found between the neuroticism in the Big Five Personality Inventory and the symptoms assessed by the DEQS (r = -0.35, p < 0.01), and the OSDI (r = -0.28, p < 0.05). There was no significant correlation observed between the signs and the symptoms, or between the signs and any personality traits. The results of our current study suggest that the personality of the patient, which appears to be the basis of various psychological factors, can have some impact on the subjective symptoms. This may be one of the reasons why there has been little association noted between the signs and symptoms of DED.