5-HT1B 1D AGONIST CGS-12066B ATTENUATES CLASP KNIFE REFLEX IN THE CAT/

1. The effect of intrathecal injection of the selective serotonin (S-H T)1B/1D receptor agonist CGS-12066B maleate (825 Mmol) was assessed on stretch-evoked clasp knife inhibition of hindlimb ankle extensor musc le reflex force in precollicular decerebrate cats in which neural tran smission in dorsolateral spinal pathways was blocked bilaterally by fo cal cooling. 2. During cold block, ramp and hold stretches of the medi al gastrocnemius muscle (MG) evoked only a brief reflex excitation tha t was followed by powerful, long-lasting inhibition (the clasp knife r eflex). Both the amplitudes of peak force evoked by the ramp and susta ined force output during the last 500 ms of the hold phase of the stre tch were depressed by >50%. 3. Reflex force output during the hold por tion of stretch was significantly improved on postdrug cold block tria ls, although peak force remained depressed. CGS-12066B did not signifi cantly alter stretch-evoked force output in decerebrate cats when spin al cord neural transmission was unimpaired. 4. These data suggest that selective 5-HT1B/LD agonists may be of therapeutic usefulness in the treatment of reflex disorders arising from partial spinal cord injury.