title: Capsaicin facilitates excitatory but not inhibitory synaptic transmission in substantia gelatinosa of the rat spinal cord.
abstract: Actions of capsaicin were examined on synaptic transmissions in the substantia gelatinosa (SG) of adult rat spinal cord slices using the whole-cell patch-recording technique. Bath-applied capsaicin at a concentration of 2 microM activated a slow inward current (having an amplitude of 33 pA at -70 mV), which was accompanied by an increase in the frequency of glutamatergic spontaneous excitatory postsynaptic currents (sEPSCs; by 234%); these actions were blocked by a capsaicin-receptor antagonist, capsazepine (10 microM). The capsaicin-induced increase in sEPSC frequency was resistant to tetrodotoxin (0.5-1 microM). On the other hand, capsaicin (2 microM) did not affect either glycine- or gamma-aminobutyric acid-mediated spontaneous synaptic transmission. The results indicate that capsaicin enhances excitatory but not inhibitory synaptic transmission, possibly through a direct action on primary afferent terminals in the SG. As the SG has been thought to participate in nociceptive pathway, it is suggested that such a presynaptic action of capsaicin contributes to nociceptive transmissions.
authors.affiliation: Department of Physiology, Saga Medical School, Nabeshima, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Yang
authors.forename: E
authors.initials: E
authors.lastname: Kumamoto
authors.forename: H
authors.initials: H
authors.lastname: Furue
authors.forename: M
authors.initials: M
authors.lastname: Yoshimura
mesh_terms: D000818:Animals; D002211:Capsaicin / Q000494:pharmacology*; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects*; D005998:Glycine / Q000502:physiology; D009433:Neural Inhibition / Q000187:drug effects* / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D013376:Substantia Gelatinosa / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects* / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000502:physiology
chemical_list: D013779:Tetrodotoxin; D005680:gamma-Aminobutyric Acid; D002211:Capsaicin; D005998:Glycine