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The Journal of Neuroscience, August 24, 2005, 25(34):7876-7886; doi:10.1523/JNEUROSCI.1178-05.2005
Previous Article
Behavioral/Systems/Cognitive
Serotonin Shifts First-Spike Latencies of Inferior Colliculus Neurons
Laura M. Hurley1 and
George D. Pollak2
1Biology Department, Indiana University, Bloomington, Indiana 47405, and 2Section of Neurobiology, University of Texas, Austin, Texas 78712
Many studies of neuromodulators have focused on changes in the magnitudes of neural responses, but fewer studies have examined neuromodulator effects on response latency. Across sensory systems, response latency is important for encoding not only the temporal structure but also the identity of stimuli. In the auditory system, latency is a fundamental response property that varies with many features of sound, including intensity, frequency, and duration. To determine the extent of neuromodulatory regulation of latency within the inferior colliculus (IC), a midbrain auditory nexus, the effects of iontophoretically applied serotonin on first-spike latencies were characterized in the IC of the Mexican free-tailed bat. Serotonin significantly altered the first-spike latencies in response to tones in 24% of IC neurons, usually increasing, but sometimes decreasing, latency. Serotonin-evoked changes in latency and spike count were not always correlated but sometimes occurred independently within individual neurons. Furthermore, in some neurons, the size of serotonin-evoked latency shifts depended on the frequency or intensity of the stimulus, as reported previously for serotonin-evoked changes in spike count. These results support the general conclusion that changes in latency are an important part of the neuromodulatory repertoire of serotonin within the auditory system and show that serotonin can change latency either in conjunction with broad changes in other aspects of neuronal excitability or in highly specific ways.
Key words: latency; inferior colliculus; auditory; serotonin; neuromodulation; sensory
Received March 25, 2005;
revised July 19, 2005;
accepted July 20, 2005.
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