Recent studies have emphasized the role of signals that travel from a
target cell, in a retrograde direction, to cells that synapse on the t
arget and influence their output. While the focus of most research on
this topic has been on long-lasting alterations at excitatory synapses
, evidence that implicates retrograde transmission in the transient re
duction of GABA(A)-receptor-mediated inhibition in hippocampus and cer
ebellum has begun to accumulate. Brief depolarizations of the postsyna
ptic principal cells lead to increases in the intracellular concentrat
ion of Ca2+, and a reduction in GABA(A)-receptor-mediated responses fo
r 1-2 min. No concomitant reduction in postsynaptic GABA(A)-receptor r
esponsiveness has been detected. Rather, release of GABA from inhibito
ry-interneuron terminals appears to be reduced. The properties of this
'depolarization-induced suppression of inhibition' might be appropria
te for unique physiological roles.