These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Double-pulse stimulation of startle-like responses in rats: refractory periods and temporal summation.
    Author: Yeomans JS, Rosen JB, Barbeau J, Davis M.
    Journal: Brain Res; 1989 May 01; 486(1):147-58. PubMed ID: 2720426.
    Abstract:
    A startle-like response was evoked by electrical stimulation with one pulse in several brainstem sites of the primary acoustic startle circuit. If a second pulse was delivered 0.4-10 ms after the first pulse, a stronger response or a decreased current threshold resulted. The facilitatory effect of the second pulse increased as interpulse (C-T) interval increased from 0.4 to 2.0 ms in cochlear nucleus or ventral lateral lemniscus sites. In caudal pontine reticular formation sites, the effect of the second pulse increased sharply from 0.3 to 0.5 ms. These results suggest that very short refractory period axons mediate electrically elicited startle in reticular formation, and that longer refractory period axons mediate startle in cochlear nucleus or ventral lateral lemniscus. In reticular formation sites, the effect of the second pulse declined nearly exponentially from 2.0 to 50 ms with a time constant of about 4 ms. Stimulation of similar reticular formation sites in cats evokes monosynaptic EPSPs in spinal motoneurons with an almost identical time course, as reported by other investigators. This suggests that the startle response evoked from the reticular formation results from monosynaptic activation of spinal motoneurons. Temporal summation declined more slowly and irregularly in cochlear nucleus and ventral lateral lemniscus sites, suggesting that these sites are not monosynaptically connected with spinal motoneurons, a conclusion consistent with anatomical data. In reticular formation sites near the facial nerve, a second peak in the two-pulse curve was observed at a C-T interval of 10 ms. The second peak was blocked by local anesthesia of the face ipsilateral to the stimulating electrode, suggesting that a single twitch of facial muscles facilitates startle.
    [Abstract] [Full Text] [Related] [New Search]