Analysis of interneurons of the rat piriform cortex : morphology, innervation, calcium binding protein expression and co-expression

Piriform cortex (PC) receives sensory input from olfactory areas, passes this onto cortical/subcortical structures and is integrated with behavioural modalities. Little is known about functional/anatomical connections of the PC. Sensory/behavioural olfactory pathways and altered interneuron wiring may facilitate the region's seizurogenic tendencies. Innervation-pattern description of the various interneurons was the objective.Distinct interneurons express differing calcium binding proteins (CBPs). Antibodies against these were used to characterise interneuron anatomical/morphological/innervation patterns. Parameters investigated for each interneuron subtype were: laminar  distribution; CBP expression overlap; dendritic arborization patterns; and post-synaptic targets of nerve terminals (NTs). These were quantified to establish a baseline, and combined to identify subtypes within the CBP-expressing groups.Only PV and CB were co-expressed in interneurons. For each subtype specific laminar distribution of somata/dendritic processes/NTs; specific dendritic arborization patterns and post-synaptic morphological targeting was found. Findings were examined within context of olfactory processing, seizurogenesis and existing olfactory cortex connectivity models.