Taurine activates excitatory non-synaptic glycine receptors on dopamine neurones in ventral tegmental area of young rats.
The physiological and pharmacological properties of taurine-induced responses were investigated in dopaminergic (DA) neurones from the ventral tegmental area (VTA) of young rats aged 1-13 postnatal days, either in acute brain slices or acutely dissociated neurones. When whole-cell responses were recorded from current-clamped neurones using the gramicidin-perforated technique, the application of taurine (0.01-30 mm) accelerated firings and induced membrane depolarization. In voltage-clamped neurones, taurine induced a current which was antagonized by strychnine and by picrotoxin, but not by bicuculline. In addition, taurine-induced current showed complete cross-desensitization with glycine-activated currents but not with gamma-aminobutyric acid (GABA)-activated currents. Thus, taurine is a full agonist of the glycine receptors (GlyRs) in the VTA. Further studies found that taurine acted mainly on non-synaptic GlyRs. The application of 20 microm bicuculline abolished the spontaneous inhibitory post-synaptic currents (IPSCs) in 40/45 neurones, and 93% of the evoked IPSCs. The addition of 1 microm strychnine completely eliminated the remaining IPSCs. These results suggest that GABAergic IPSCs predominate, and that functional glycinergic synapses are present in a subset of the VTA neurones. The application of 1 mum strychnine alone induced an outward current, suggesting that these neurones were exposed to tonically released taurine/glycine. In conclusion, by activating non-synaptic GlyRs, taurine may act as an excitatory extra-synaptic neurotransmitter in the VTA during early development.
Wang
Fushun
F
New Jersey Medical School (UMDNJ), 185 South Orange Avenue, Newark, NJ 07103-2714, USA.
Xiao
Cheng
C
Ye
Jiang Hong
JH
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000367:Age Factors; D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D003292:Convulsants / Q000494:pharmacology; D004298:Dopamine / Q000502:physiology*; D005998:Glycine / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D018408:Patch-Clamp Techniques; D010852:Picrotoxin / Q000494:pharmacology; D051381:Rats; D018009:Receptors, Glycine / Q000502:physiology*; D013331:Strychnine / Q000494:pharmacology; D013654:Taurine / Q000494:pharmacology*; D017557:Ventral Tegmental Area / Q000166:cytology / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D001640:Bicuculline; D003292:Convulsants; D004298:Dopamine; D005998:Glycine; D010852:Picrotoxin; D018009:Receptors, Glycine; D013331:Strychnine; D013654:Taurine; D005680:gamma-Aminobutyric Acid