The action of substance P methyl ester on cochlear potentials in the guinea pig.
The action of the substance P agonist, substance P methyl ester (SPME) on cochlear potentials was examined in the guinea pig. Previous studies have shown that SPME is a selective agonist for neurokinin 1 (NK1) receptor. Perfusion with SPME at a concentration of more than 10(-6)M produced an increase in the amplitudes of the compound action potential and negative summating potential in a dose-dependent manner. N1 latency showed a tendency to be shortened, but this change was not significant. Amplitudes of the cochlear microphonics and endocochlear potential remained unchanged. Substance P fragment 7-11, an inactive analogue, produced no changes in the cochlear potentials. In contrast, the substance P antagonist [D-Pro2, D-Trp7,9]-SP blocked the action of SPME on the cochlear potentials. These results suggest that substance P may modulate neurotransmission through NK1 receptors in the cochlea.
Nario
K
K
Department of Otolaryngology, Nara Medical University, Japan.
Kitano
I
I
Mori
N
N
Matsunaga
T
T
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D003051:Cochlea / Q000187:drug effects* / Q000502:physiology; D003055:Cochlear Microphonic Potentials / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D015288:Neurokinin A / Q000037:antagonists & inhibitors; D015287:Neurokinin B / Q000037:antagonists & inhibitors; D010446:Peptide Fragments / Q000494:pharmacology; D011930:Reaction Time / Q000187:drug effects; D018041:Receptors, Neurokinin-2 / Q000037:antagonists & inhibitors; D018042:Receptors, Neurokinin-3 / Q000037:antagonists & inhibitors; D013373:Substance P / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000494:pharmacology
D010446:Peptide Fragments; D018041:Receptors, Neurokinin-2; D018042:Receptors, Neurokinin-3; D013373:Substance P; C061335:substance P (7-11); C033611:substance P, methyl ester-; C032132:substance P, prolyl(2)-tryptophan(7,9)-; D015288:Neurokinin A; D015287:Neurokinin B