Serotonin inhibits high-threshold Ca2+ channel currents in capsaicin-sensitive acutely isolated adult rat DRG neurons.
1. The effect of serotonin (5HT) was studied on high-threshold Ca2+ channel currents in a subpopulation of acutely isolated rat dorsal root ganglion cell bodies that had long-duration action potentials, lacked IH current, were capsaicin-sensitive, and thus resembled C-type nociceptors. 2. In these neurons, 10 microM 5HT inhibited peak high-threshold Ca2+ channel currents by 61.5 +/- 6.9% (mean +/- SE), (n = 7). The effects of 5HT were mimicked by 1 microM (+)8-hydroxy-2-(di-n-propylamino)-tetralin HBr [(+)8-OH-DPAT] in five neurons tested, and the effects of 1 microM (+)8-OH-DPAT were antagonized by 100 nM 1-(2-methoxyphenyl)-4-[4-(2-phthalimmido)butyl]piperazine HBr (NAN-190) in six neurons tested. 3. The above data leads us to hypothesize that 5HT, released into the spinal cord by descending systems, may produce antinociception by inhibiting Ca2+ entry into afferent terminals of nociceptors via activation of 5HT1A receptors.
Del Mar
L P
LP
Department of Anatomy and Neurobiology, University of Tennessee, Memphis 38165.
Cardenas
C G
CG
Scroggs
R S
RS
D000344:Afferent Pathways / Q000187:drug effects / Q000502:physiology; D000818:Animals; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002211:Capsaicin / Q000494:pharmacology*; D005727:Ganglia, Spinal / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011985:Receptors, Serotonin / Q000187:drug effects / Q000502:physiology; D012701:Serotonin / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*
D015220:Calcium Channels; D011985:Receptors, Serotonin; D012701:Serotonin; D002211:Capsaicin