The neuronal generators of the b- and d-waves
of the electroretinogram (ERG) were investigated in the
tiger salamander retina to determine if amacrine and ganglion
cells contribute to this field potential. Several agents
were used that affect third-order neurons, such as tetrodotoxin,
baclofen, and NMDA agonists and antagonists. Baclofen,
an agent that enhances light responses in third-order neurons,
increased the d-wave and reduced the b-wave.
In contrast, agents that decrease light responses in third-order
neurons had the opposite effect of enhancing the b-wave
and depressing the d-wave. The effect on the d-wave
was particularly pronounced. The results indicate that
third-order neuronal activity influences b- and
d-waves of the ERG. The opposing actions suggest
that the b-wave to d-wave ratio might
serve as an measure of ganglion cell function.