Cholinergic neurotransmission in retinal spreading depression

Summary Experiments performed to demonstrate the participation of cholinergic synapses in retinal spreading depression (SD) have shown that: (1) acetylcholine (ACh) is liberated during SD, its concentration increasing up to 10 ^-4 mM in the superfusate of one eye cup; (2) the susceptibility of the retina to SD and the velocity of propagation of circling SD are influenced by cholinergic and anticholinergic drugs. ACh 1 mM is effective in eliciting the reaction, whereas d-tubocurarine 0.01 mM and atropine 0.25 mM block this effect. Prostigmine 0.075 mM is able to trigger the reaction and also potentiates the effect of ACh. The velocity of propagation is decreased by ACh 0.25–1.0 mM and prostigmine 0.030 mM, which also potentiate this effect of ACh. Pulses of d-tubocurarine 0.005–0.030 mM and atropine 0.025–0.30 mM decrease the velocity of propagation. However, they block the effect of ACh if they are continuously present in the superfusing solution; (3) the effects of ACh are not blocked by tetrodotoxin 3.19×10^-3 mM.