ACTIONS OF GLYCINE ON NONDOPAMINERGIC NEURONS OF THE RAT SUBSTANTIA-NIGRA

The effects of glycine on non-dopaminergic cells in rat substantia nig ra pars compacta and pars reticulata maintained in vitro were investig ated using intracellular recording techniques. Glycine, superfused at a concentration between 30 mu M and 1 mM, reversibly blocked the spont aneous firing of these neurons. The inhibition of firing discharge was associated with a hyperpolarization of the membrane (potassium acetat e-filled electrodes) and an increase in conductance. Under voltage-cla mp experiments (holding potential between -57 and -65 mV), glycine pro duced an outward response which reversed polarity at about -74 mV. How ever, when the recording electrodes were filled with KCl, the glyciner gic response was mainly depolarizing/inward and reversed at about -43 mV. Thus, it appeared to be due to an increase in chloride permeabilit y. Furthermore, the effects of glycine were reversibly antagonized by strychnine (between 300 nM and 1 mu M). Our findings demonstrate that glycine is a potent inhibitory agent on non-dopaminergic cells of the substantia pars compacta and pars reticulata that acts by activating s trychnine-sensitive receptors.