title: Efferent fibers innervate gustatory and mechanosensitive afferent fibers in frog fungiform papillae.
abstract: A possibility of efferent innervation of gustatory and mechanosensitive afferent fiber endings was studied in frog fungiform papillae with a suction electrode. The amplitude of antidromic impulses in a papillary afferent fiber induced by antidromically stimulating an afferent fiber of glossopharyngeal nerve (GPN) with low voltage pulses was inhibited for 40 s after the parasympathetic efferent fibers of GPN were stimulated orthodromically with high voltage pulses at 30 Hz for 10 s. This implies that electrical positivity of the outer surface of papillary afferent membrane was reduced by the efferent fiber-induced excitatory postsynaptic potential. The inhibition of afferent responses in the papillae was blocked by substance P receptor blocker, L-703,606, indicating that substance P is probably released from the efferent fiber terminals. Slow negative synaptic potential, which corresponded to a slow depolarizing synaptic potential, was extracellularly induced in papillary afferent terminals for 45 s by stimulating the parasympathetic efferent fibers of GPN with high voltage pulses at 30 Hz for 10 s. This synaptic potential was also blocked by L-703,606. These data indicate that papillary afferent fiber endings are innervated by parasympathetic efferent fibers.
authors: Division of Integrative Sensory Physiology, Nagasaki University Graduate School of Biomedical Sciences, 1-7-1 Sakamoto, Nagasaki 852-8588, Japan. toshi@net.nagasaki-u.ac.jp
authors: Toshihide
authors: T
authors: Sato
authors: Kazuhisa
authors: K
authors: Nishishita
authors: Yukio
authors: Y
authors: Okada
authors: Kazuo
authors: K
authors: Toda
mesh_terms: D000200:Action Potentials; D000344:Afferent Pathways / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D004525:Efferent Pathways / Q000187:drug effects / Q000502:physiology*; D004558:Electric Stimulation; D004566:Electrodes; D005930:Glossopharyngeal Nerve / Q000187:drug effects / Q000502:physiology; D040542:Mechanotransduction, Cellular / Q000187:drug effects / Q000502:physiology*; D009412:Nerve Fibers / Q000187:drug effects / Q000502:physiology*; D011812:Quinuclidines / Q000494:pharmacology; D011892:Rana catesbeiana / Q000502:physiology*; D013373:Substance P / Q000037:antagonists & inhibitors / Q000502:physiology; D055366:Synaptic Potentials; D013650:Taste Buds / Q000187:drug effects / Q000502:physiology; D055697:Taste Perception / Q000187:drug effects / Q000502:physiology*
chemical_list: D011812:Quinuclidines; C076851:L 703606; D013373:Substance P