Time-dependent phrenic nerve responses to carotid afferent activation: intact vs. decerebellate rats

Am J Physiol. 1993 Oct;265(4 Pt 2):R811-9. doi: 10.1152/ajpregu.1993.265.4.R811.


The objectives were to determine 1) respiratory responses to carotid chemoreceptor inputs in anesthetized rats and 2) whether the cerebellar vermis plays a role in these responses. A carotid sinus nerve was stimulated (20 Hz) with five 2-min trains, each separated by approximately 3 min. During stimulation, respiratory frequency (f), peak amplitude of integrated phrenic nerve activity (integral of Phr), and their product (f x integral of Phr) immediately increased. As stimulation continued, integral of Phr progressively increased to a plateau [short-term potentiation (STP)], but f and f x integral of Phr decreased [short-term depression (STD)] to a value still above control. Upon stimulus termination, integral of Phr progressively decreased but remained above control; f and f x integral of Phr transiently decreased below baseline. After the final stimulation, integral of Phr remained above control for at least 30 min [long-term facilitation (LTF)]. Repeated 5-min episodes of isocapnic hypoxia also elicited STP, STD, and LTF. Vermalectomy lowered the CO2-apneic threshold and eliminated LTF. In conclusion, carotid chemoreceptor activation in rats elicits STP and LTF similar to that in cats; the vermis may play a role in LTF. A new response, STD, was observed.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Afferent Pathways / physiology
  • Animals
  • Blood Pressure / physiology
  • Carotid Sinus / innervation*
  • Cerebellum / physiology*
  • Decerebrate State*
  • Electric Stimulation
  • Hypoxia / physiopathology
  • Male
  • Phrenic Nerve / physiology*
  • Pressoreceptors / physiology
  • Rats
  • Rats, Sprague-Dawley
  • Reference Values
  • Time Factors