Deprivation of spontaneous rhythmic electrical activity in early development by anesthesia administration, among other interventions, induces neuronal apoptosis. However, it is unclear whether enhancement of neuronal electrical activity attenuates neuronal apoptosis in either normal development or after anesthesia exposure. The present study investigated the effects of dopamine, an enhancer of spontaneous rhythmic electrical activity, on ketamine-induced neuronal apoptosis in the developing rat retina. TUNEL and immunohistochemical assays indicated that ketamine time- and dose-dependently aggravated physiological and ketamine-induced apoptosis and inhibited early-synchronized spontaneous network activity. Dopamine administration reversed ketamine-induced neuronal apoptosis, but did not reverse the inhibitory effects of ketamine on early synchronized spontaneous network activity despite enhancing it in controls. Blockade of D1, D2, and A2A receptors and inhibition of cAMP/PKA signaling partially antagonized the protective effect of dopamine against ketamine-induced apoptosis. Together, these data indicate that dopamine attenuates ketamine-induced neuronal apoptosis in the developing rat retina by activating the D1, D2, and A2A receptors, and upregulating cAMP/PKA signaling, rather than through modulation of early synchronized spontaneous network activity.

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Apoptosis has been identified as the primary cause of fetal alcohol spectrum disorder (FASD), and the development of methods to prevent and treat FASD have been based on the mechanisms of alcohol-induced apoptosis. The present study aimed to explore the effects of dopamine on alcohol-induced neuronal apoptosis using whole-mount cultures of rat retinas (postnatal day 7). Retinas were initially incubated with ethanol (100, 200 or 500 mM), and in subsequent analyses retinas were co-incubated with ethanol (200 mM) and dopamine (10 µM). In addition, several antagonists and inhibitors were used, including a D1 dopamine receptor (D1R) antagonist (SCH23390; 10 µM), a D2R antagonist (raclopride; 40 µM), an adenosine A2A receptor (AA2AR) antagonist (SCH58261; 100 nM), an adenylyl cyclase (AC) inhibitor (SQ22536; 100 µM) and a PKA inhibitor (H-89; 1 µM). The results demonstrated that exposure increased neuroapoptosis in the retinal ganglion cell layer (GCL) in a dose-dependent manner. Dopamine treatment significantly attenuated ethanol-induced neuronal apoptosis. D1R, D2R and AA2AR antagonists partially inhibited the protective effects of dopamine against ethanol-induced apoptosis; similar results were observed with AC and PKA inhibitor treatments. In summary, the present study demonstrated that dopamine treatment may be able to attenuate alcohol-induced neuroapoptosis in the developing rat retina by activating D1R, D2R and AA2AR, and by upregulating cyclic AMP/protein kinase A signaling.