INHIBITORY LONG-TERM POTENTIATION UNDERLIES AUDITORY CONDITIONING OF GOLDFISH ESCAPE BEHAVIOR

Long-term potentiation (LTP), the increase in synaptic strength evoked by high-frequency stimulation, is often considered to be a cellular m odel for learning and memory. The validity of this model depends on th e assumptions that physiological stimuli can induce LTP in vivo and th at the resulting: synaptic modifications correlate with behavioural ch anges. However, modifiable synapses are generally embedded deep in com plex circuits. In contrast, the goldfish Mauthner (M)-cell and its aff erent synapses are easily accessible for electrophysiological studies, and firing of this neuron is sufficient to trigger fast escape behavi our in response to sudden stimuli(1,2). We have previously shown that tetanic stimulation can induce LTP of the feedforward inhibitory synap ses that control the excitability of the M-ceIl(3,4). Here we report t hat natural sensory stimulation can induce potentiation of this inhibi tory connection that resembles the LTP induced by afferent tetanizatio n. Furthermore, comparable acoustic stimulation produced a parallel de crease in the probability of the sound-evoked escape reflex Thus we de monstrate for the first time, to our knowledge, a behavioural role for the long-term synaptic strengthening of inhibitory synapses.