DISTRIBUTION OF THE METABOTROPIC GLUTAMATE-RECEPTOR SUBTYPE MGLUR5 INRAT MIDBRAIN PERIAQUEDUCTAL GREY AND RELATIONSHIP WITH ASCENDING SPINOFUGAL AFFERENTS

The periaqueductal grey matter (FAG) is known to adjust somatic and ne urovegetative elements of the defence behaviour. We have used specific polyclonal antibodies to examine the distribution of the metabotropic glutamate receptor subtype 5 (mGluR5) in this region. Immunolabelling for mGluR5 displayed a net preference for dorsolateral areas at rostr al and intermediate levels. Electronmicroscopic examination revealed t hat mGluR5 is expressed in neuronal perikarya and in dendrites receivi ng synaptic contacts of Gray I type. To investigate the possible relev ance of mGluR5 to integration of somatosensory information, spinoannul ar (SA) neurones were peroxidase-labelled and their relationship with mGluR5-expressing FAG neurones was examined at the ultrastructural lev el. A number of synaptic terminals of the SA pathway established synap tic contact of asymmetric type onto mGluR5-immunoreactive dendrites. I t is suggested that mGluR5 might be involved in the temporal integrati on of somatosensory inputs to the FAG. (C) 1997 Elsevier Science Irela nd Ltd.