Actions of glycine on non-dopaminergic neurons of the rat substantia nigra.
The effects of glycine on non-dopaminergic cells in rat substantia nigra pars compacta and pars reticulata maintained in vitro were investigated using intracellular recording techniques. Glycine, superfused at a concentration between 30 microM and 1 mM, reversibly blocked the spontaneous firing of these neurons. The inhibition of firing discharge was associated with a hyperpolarization of the membrane (potassium acetate-filled electrodes) and an increase in conductance. Under voltage-clamp experiments (holding potential between -57 and -65 mV), glycine produced an outward response which reversed polarity at about -74 mV. However, when the recording electrodes were filled with KCl, the glycinergic response was mainly depolarizing/inward and reversed at about -43 mV. Thus, it appeared to be due to an increase in chloride permeability. Furthermore, the effects of glycine were reversibly antagonized by strychnine (between 300 nM and 1 microM). Our findings demonstrate that glycine is a potent inhibitory agent on non-dopaminergic cells of the substantia pars compacta and par reticulata that acts by activating strychnine-sensitive receptors.
Mercuri
N B
NB
Clinica Neurologica, Università di Roma Tor Vergata, Italy.
Bonci
A
A
Pisani
A
A
Calabresi
P
P
Bernardi
G
G
D000818:Animals; D004298:Dopamine / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005998:Glycine / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects*; D009474:Neurons / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D013378:Substantia Nigra / Q000187:drug effects*
D005998:Glycine; D004298:Dopamine