Premium
Glycine activates myenteric neurones in adult guinea‐pigs
Author(s) -
Neunlist Michel,
Michel Klaus,
Reiche Dania,
Dobreva Gisela,
Huber Korinna,
Schemann Michael
Publication year - 2001
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2001.00727.x
Subject(s) - guinea pig , myenteric plexus , glycine , chemistry , neuroscience , biology , medicine , endocrinology , immunohistochemistry , biochemistry , amino acid
1 We studied the effects of glycine on myenteric neurones and muscle activity in the colon and stomach of adult guinea‐pigs. 2 Intracellular recordings revealed that myenteric neurones responded to local microejection of glycine (1 m m ) with a fast, transient membrane potential depolarisation (57 % of 191 colonic neurones and 26 % of 50 gastric neurones). Most glycine‐sensitive neurones had ascending projections and were choline acetyltransferase immunoreactive. Glycine preferentially activated neurones with a late afterhyperpolarisation (AH‐neurones) and tonic spiking neurones with fast synaptic inputs (tonic S‐neurones) but less frequently phasic S‐neurones and inexcitable (non‐spiking) neurones. The depolarisation had a reversal potential at −19 ± 13 mV, which was increased by 18 ± 10 % upon lowering extracellular chloride concentration and decreased by 38 ± 14 % in furosemide (frusemide, 2 m m ). 3 Strychnine (300 n m ) reversibly abolished the glycine‐induced depolarisation and the Cl − channel blocker picrotoxin (100 μ m ) reduced the amplitude of the depolarisation by 55 ± 5 %. The glycine effect was a postsynaptic response because it was not changed after nerve blockade with tetrodotoxin (1 μ m ) or blockade of synaptic transmission in reduced extracellular [Ca 2+ ]. The effect was specific since the response was not changed by the nicotinic antagonists hexamethonium (200 μ m ) and mecamylamine (100 μ m ), the GABA A receptor antagonist bicuculline (10 μ m ), the NMDA antagonist MK‐801 (20 μ m ) or the 5‐HT 3 antagonist ICS 205930 (1 μ m ). 4 Glycine (1 m m ) induced a tetrodotoxin‐ and strychnine‐sensitive contractile response in the colon; the contractile response in the stomach was tetrodotoxin insensitive. 5 Glycine activated myenteric neurones in the adult enteric nervous system through strychnine‐sensitive mechanisms. The glycine‐evoked depolarisation was caused by Cl − efflux and the maintenance of relatively high intracellular chloride concentrations involved furosemide‐sensitive cation‐chloride co‐transporters.