Glycine: an alternative transmitter candidate of the pallidosubthalamic projection neurons in the rat.
Autoradiographic retrograde tracing techniques with radioactive transmitters were used to analyse the identity of a putative transmitter in the rat pallidosubthalamic (GP-STN) pathway. One to 2 hours after the stereotaxic injection of 3H-glycine restricted to the STN, a large number of neuronal somata were radiolabeled in the GP. No comparable labeling was observed following the injection of 3H-gamma-aminobutyric acid (3H-GABA) into the same nucleus even with survival times as long as 6 hours. Specifically, no significant somatic labeling was detected either in the GP or in the caudoputamen (CPU). Only when 3H-GABA was injected into the substantia nigra did CPU and GP neurons become labeled. On the contrary, STN neuronal somata were invariably labeled 6 hours after the intrapallidal injection of 3H-GABA, whereas no perikaryal labeling was observed in the STN after 3H-glycine injection into the GP. The perikaryal labeling was prevented in all cases by intraventricular administration of colchicine 1 day before the isotope injections. The observations suggest that 3H-glycine was preferentially transported retrogradely through the GP-STN pathway, and 3H-GABA through the STN-GP projection. In view of the recent controversy on the role of GABA as a putative transmitter of the GP-STN projection, we now propose glycine as an alternative transmitter candidate of these critically situated neurons in the basal ganglia.
D000818:Animals; D001345:Autoradiography; D005917:Globus Pallidus / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D005998:Glycine / Q000493:pharmacokinetics / Q000502:physiology*; D008297:Male; D009474:Neurons / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000502:physiology*; D051381:Rats; D009435:Synaptic Transmission; D013788:Thalamus / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D014316:Tritium; D005680:gamma-Aminobutyric Acid / Q000493:pharmacokinetics
D018377:Neurotransmitter Agents; D014316:Tritium; D005680:gamma-Aminobutyric Acid; D005998:Glycine