Fear conditioning, pre-pulse inhibition and drug modulation of a short latency startle response measured electromyographically from neck muscles in the rat.

The present study evaluated if startle measured electromyographically in the neck muscles (having a 5 msec latency) would exhibit behavioral and pharmacological plasticity known to alter startle measured in a stabilimeter device. A total of 15 rats were implanted with bilateral EMG electrodes in the dorsal neck muscles and subsequently exposed to a variety of manipulations known to affect the whole-body startle response. The peak-to-peak EMG response that occurred within 10 msec of startle stimulus onset displayed pre-pulse inhibition, enhancement by prior fear conditioning, inhibition by clonidine, and enhancement by strychnine. The data are discussed in terms of modulation of neural transmission along a primary startle-mediating pathway.