Journal of Neurophysiology, Vol 74, Issue 1 453-456, Copyright © 1995 by APS
5-HT1B/1D agonist CGS-12066B attenuates clasp knife reflex in the cat
J. F. Miller, K. D. Paul, W. Z. Rymer and C. J. Heckman
Veterans Administration, Lakeside Hospital, Chicago, Illinois, USA.
1. The effect of intrathecal injection of the selective serotonin
(5-HT)1B/1D receptor agonist CGS-12066B maleate (825 nmol) was assessed on
stretch-evoked clasp knife inhibition of hindlimb ankle extensor muscle
reflex force in precollicular decerebrate cats in which neural transmission
in dorsolateral spinal pathways was blocked bilaterally by focal cooling.
2. During cold block, ramp and hold stretches of the medial gastrocnemius
muscle (MG) evoked only a brief reflex excitation that was followed by
powerful, long-lasting inhibition (the clasp knife reflex). Both the
amplitudes of peak force evoked by the ramp and sustained force output
during the last 500 ms of the hold phase of the stretch were depressed by
> 50%. 3. Reflex force output during the hold portion of stretch was
significantly improved on postdrug cold block trials, although peak force
remained depressed. CGS-12066B did not significantly alter stretch-evoked
force output in decerebrate cats when spinal cord neural transmission was
unimpaired. 4. These data suggest that selective 5-HT1B/1D agonists may be
of therapeutic usefulness in the treatment of reflex disorders arising from
partial spinal cord injury.
