Abstract
Abstract: :
Purpose: To examine the effect of olfactory centrifugal input on retinal ganglion cell (RGC) sensitivity and spike activity, and to investigate the mechanism underlying olfactory–retinal signaling transmission. Methods: RGC activities were recorded from the optic nerve. Light thresholds that elicit threshold spikes (criteria, 20% greater than the spontaneous firing) were measured before and after olfactory stimulation. Odors (1.0 mM methionine) were delivered via a micropipette to the nostril contralateral to the recording eye. Intracellular calcium concentrations were determined by time lapse imaging. Results: Olfactory stimulation increased RGC sensitivity by 0.53 log units and its firing by 49.8%. In the presence of dopamine D1 receptor antagonist, however, olfactory stimulation resulted in no effect on RGC activity. Intraocular injections of dopamine decreased RGC sensitivity by 0.75 log units and its firing by 50.9%. In cultured cells, dopamine decreased RGC calcium concentration by 32.0%. Conclusions: The effect of olfactory stimulation on RGC is mediated by dopamine. In zebrafish as well as in several other teleost species, dopamine has been shown to decrease RGC activity.
Keywords: ganglion cells • dopamine • retina: proximal (bipolar, amacrine, and ganglion cells)