Excitatory responses of trigeminal neurons to substance P suggest involvement in sensory transmission.
Responses to substance P application were studied with intracellular recording techniques in in vitro preparations of trigeminal root ganglion neurons of guinea pigs. Perfusion of substance P in micromolar concentrations markedly depolarized neurons and reduced their input conductances. Also, the threshold for spikes evoked by injections of depolarizing current pulses was decreased. Single electrode voltage-clamp recordings showed that substance P increased inward, and decreased outward currents evoked by hyperpolarizing voltage steps from holding potentials near rest. Depolarizing responses to substance P were attenuated in Na+-deficient solutions. The excitatory actions of this endogenous peptide on the perikarya of primary sensory neurons give rise to the possibility of physiological actions of substance P at multiple sites in the trigeminal system.
Spigelman
I
I
Department of Pharmacology and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver, Canada.
Puil
E
E
D000818:Animals; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008564:Membrane Potentials; D009475:Neurons, Afferent / Q000502:physiology*; D013373:Substance P / Q000502:physiology*; D009435:Synaptic Transmission; D014276:Trigeminal Nerve / Q000166:cytology / Q000502:physiology*
D013373:Substance P