title: Cannabinoid CB1 receptors in rat medial prefrontal cortex are colocalized with calbindin- but not parvalbumin- and calretinin-positive GABA-ergic neurons.
abstract: In the present study, we investigate putative localization of cannabinoid receptors 1 (CB1) protein on a population of cortical gamma-aminobutyric acid (GABA) - positive interneurons characterized by expression of calcium-binding proteins in rat medial prefrontal cortex (MPC). Parvalbumin (PARV)/calretinin (CALR)- and calbindin (CALB)-positive neurons form two distinct populations of GABA-ergic interneurons that comprise the axo-somatic/axo-axonic and axo-dendritic inhibitory systems of pyramidal cells. It has been found that CB1 receptor-positive cells are randomly distributed across the rat MPC. All spotted neurons that were positive for CB1 receptors were positive for GABA; however, the number of GABA-positive cells drastically exceeded the number of CB1 receptor-positive neurons. Subsequent experiments with double-labelling of CB1 receptors with PARV and CALR revealed no colocalization. CALB-positive neurons (e.g., double bouquet and bipolar cells) display colocalization: the degree of colocalization among CB1 receptor-positive cells reached 18%. The appearance of CB1 receptors in double bouquet and bipolar neurons indicates that CB1 receptors may control the activity of pyramidal neurons from presynaptic sites in axo-dendritic synapses formed on apical and basilar dendrites of pyramidal neurons, as is characteristic for CALB-positive cortical interneurons. The phenotype of GABA- and CB1 receptor-positive but CALB-negative neurons may represent a population of inhibitory neurons that allow axo-somatic control of information flow, governed by principal neurons of the MPC.
authors.affiliation: Laboratory of Pharmacology and Brain Biostructure, Department of Pharmacology, Institute of Pharmacology, Polish Academy of Sciences, Smetna 12, PL 31-343 Kraków, Poland. nfwedzon@cyf-kr.edu.pl
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Wedzony
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Chocyk
mesh_terms: D000818:Animals; D064032:Calbindin 2; D064026:Calbindins; D008297:Male; D009474:Neurons / Q000378:metabolism*; D010320:Parvalbumins / Q000378:metabolism; D017397:Prefrontal Cortex / Q000378:metabolism; D017966:Pyramidal Cells / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D043884:Receptor, Cannabinoid, CB1 / Q000378:metabolism*; D064030:S100 Calcium Binding Protein G / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: C576512:Calb2 protein, rat; D064032:Calbindin 2; D064026:Calbindins; D010320:Parvalbumins; D043884:Receptor, Cannabinoid, CB1; D064030:S100 Calcium Binding Protein G; D005680:gamma-Aminobutyric Acid