Paper Information

Title: 

THE GLUTAMATE-CONTAINING MESOCORTICAL PROJECTION: A COMBINED ANTEROGRADE TRACING AND IMMUNOHISTOCHEMICAL ANALYSIS

Type: POSTER
Author(s): RAJAEI Z.,GORELOVA N.A.,SEAMANS J.K.
 
 
 
Name of Seminar: IRANIAN CONGRESS OF PHYSIOLOGY AND PHARMACOLOGY
Type of Seminar:  CONGRESS
Sponsor:  PHYSIOLOGY AND PHARMACOLOGY SOCIETY, MASHHAD UNIVERSITY OF MEDICAL SCIENCE
Date:  2007Volume 18
 
 
Abstract: 

Electrophysiological evidence indicates that when the ventral tegmental area (VTA) is stimulated electrically, an EPSP recorded in prefrontal cortex pyramidal neurons is always evoked first, which is then followed by a IPSP. The presence of a fast, glutamate antagonist sensitive EPSP in the mesocortical pathway would seem to serve as evidence for release of glutamate from dopamine (DA) and/or non-DA VTA neurons. Vesicular glutamate transporter 2 (VGLUT2) mRNA is highly expressed in the VTA, especially in rostral-medial regions, but it is unclear whether this population of neurons projects to prefrontal cortex and whether these neurons are only glutamatergic or contain both glutamate and dopamine (DA). If they only contain glutamate then using tyrosine hydroxylase (TH) as a marker would yield negative results. Therefore, we used an anterograde tracer to investigate the localization of VGLUT2 in axon terminals of mesocortical neurons. Following injection of phaseolus vulgaris leucoagglutinin (PHA-L) into the rostral linear nucleus (RLi) or parabrachial pigmental area (PBP) regions of VTA, many VTA neurons were labeled locally. Using double and triple labeling with specific antibodies for PHA-L, VGLUT2 and/or TH, we found over 40% of PHA-L labeled terminals in the prefrontal cortex contained immunoreactivity for VGLUT2 with injections in the RLi producing the largest percentage (60%). Only 29% of PHA-L+ fibers in PFC were TH+, while 4-9% was both TH+ and VGLUT2+. While it is not yet clear what proportion of the non-DA fibers were GABAergic, these results suggest that glutamate could be co-released from DA terminals in the prefrontal cortex but there is a much larger projection of glutamate-containing non-DA neurons to the prefrontal cortex, with the strength and significance of the projection varying regionally within the VTA.

 
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