Immunocytochemical analysis of basket cells in rat piriform cortex

Abstract

Basket cells, defined by axons that preferentially contact cell bodies, were studied in rat piriform (olfactory) cortex with antisera to gamma-aminobutyric acid (GABA)ergic markers (GABA, glutamate decarboxylase) and to peptides and calcium binding proteins that are expressed by basket cells. Detailed visualization of dendritic and axonal arbors was obtained by silver-gold enhancement of staining for vasoactive intestinal peptide (VIP), cholecystokinin (CCK), parvalbumin, and calbindin. Neuronal features were placed into five categories: soma-dendritic and axonal morphologies, laminar distributions of dendritic and axonal processes, and molecular phenotype. Although comparatively few forms were distinguished within each category, a highly varied co-expression of features from different categories produced a "combinatorial explosion" in the characteristics of individual neurons. Findings of particular functional interest include: dendritic distributions suggesting that somatic inhibition is mediated by feedforward as well as feedback pathways, axonal variations suggesting a differential shaping of the temporal aspects of somatic inhibition from different basket cells, evidence that different principal cell populations receive input from different combinations of basket cells, and a close association between axonal morphology and molecular phenotype. A finding of practical importance is that light microscopic measurements of boutons were diagnostic for the molecular phenotype and certain morphological attributes of basket cells. It is argued that the diversity in basket cell form in the piriform cortex, as in other areas of the cerebral cortex, reflects requirements for large numbers of specifically tailored inhibitory processes for optimal operation that cannot be met by a small number of rigidly defined neuronal populations.

Developmental changes in odor-evoked activity in rat piriform cortex

“…One feature of odor-evoked activity is that the distribution of activated cells appears to have some order in the APC, where activity is concentrated in prominent rostrocaudally-oriented bands. This banding pattern is mirrored by regional differences in cytoarchitectural features and by connectivity patterns, suggesting the presence of subregions within APC (Luskin and Price, 1983;Haberly, 2001;Ekstrand et al, 2001a;Ekstrand et al, 2001b;Illig and Haberly, 2003;Illig, 2005). In PPC, however, activity appears more broadly distributed, without obvious odor-associated patterns, suggesting differences in the organization and function of APC and PPC.…”

Diverse Patterns of Odor Representation by Neurons in the Anterior Piriform Cortex of Awake Mice

“…In addition to PNs, anatomical studies have revealed multiple types of nPNs that are morphologically distinguishable (Haberly, 1983;Protopapas and Bower, 2000;Ekstrand et al, 2001). As in other cortical areas, a substantial number of nPNs are GABAergic and inhibitory in the piriform cortex.…”

Major Effects of Sensory Experiences on the Neocortical Inhibitory Circuits

“…GAD65/ 67-IR was found in cell bodies of GABAreleasing interneurons and synaptic terminals of GABA-releasing interneurons. In neocortex, abundant GAD65/67-positive GABAergic terminals were also found in perisomatic site of pyramidal neurons and spiny neurons (Fukuda et al, 1998;Ekstrand et al, 2001). Because of the close localization of these inhibitory synapses in the cell body and the basket formation of the perisomatic inhibitory synapses, the cell body of these glutamatergic cells appears to be positive for GAD65/67 (Fig.…”