5-Hydroxytryptamine reduces substance P responses on dorsal horn interneurones: a possible interaction of neurotransmitters.
Responses of dorsal horn neurons to iontophoretically administered substance P were attenuated by iontophoretically applied 5-hydroxytryptamine (5-HT). This occurred even when 5-HT alone had no effect on the excitability of the cell. 5-HT did not attenuate responses to iontophoretic application of glutamate. It has been suggested that 5-HT presynaptically inhibits the nociceptive afferents but direct application of 5-HT whilst recording the polarisation of primary afferents in vivo failed to confirm this postulate. These results cannot be explained by a presynaptic inhibition of primary afferents by 5-HT and it is suggested that 5-HT is either acting directly on the substance P receptor or on the receptor-excitation coupling mechanism.
D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D005071:Evoked Potentials; D005727:Ganglia, Spinal / Q000502:physiology*; D006614:Hindlimb / Q000294:innervation; D007395:Interneurons / Q000502:physiology*; D008297:Male; D009433:Neural Inhibition; D009619:Nociceptors / Q000502:physiology; D051381:Rats; D012701:Serotonin / Q000502:physiology*; D013373:Substance P / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000502:physiology
D012701:Serotonin; D013373:Substance P; D005680:gamma-Aminobutyric Acid