Cortical adrenoceptor expression, function and adaptation under conditions of cannabinoid receptor deletion.
A neurochemical target at which cannabinoids interact to have global effects on behavior is brain noradrenergic circuitry. Acute and repeated administration of a cannabinoid receptor synthetic agonist is capable of increasing multiple indices of noradrenergic activity. This includes cannabinoid-induced 1) increases in norepinephrine (NE) release in the medial prefrontal cortex (mPFC); 2) desensitization of cortical α2-adrenoceptor-mediated effects; 3) activation of c-Fos in brainstem locus coeruleus (LC) noradrenergic neurons; and 4) increases in anxiety-like behaviors. In the present study, we sought to examine adaptations in adrenoceptor expression and function under conditions of cannabinoid receptor type 1 (CB1r) deletion using knockout (KO) mice and compare these to wild type (WT) controls. Electrophysiological analysis of α2-adrenoceptor-mediated responses in mPFC slices in WT mice showed a clonidine-induced α2-adrenoceptor-mediated increase in mPFC cell excitability coupled with an increase in input resistance. In contrast, CB1r KO mice showed an α2-adrenoceptor-mediated decrease in mPFC cell excitability. We then examined protein expression levels of α2- and β1-adrenoceptor subtypes in the mPFC as well as TH expression in the locus coeruleus (LC) of mice deficient in CB1r. Both α2- and β1-adrenoceptors exhibited a significant decrease in expression levels in CB1r KO mice when compared to WT in the mPFC, while a significant increase in TH was observed in the LC. To better define whether the same cortical neurons express α2A-adrenoceptor and CB1r in mPFC, we utilized high-resolution immunoelectron microscopy. We localized α2A-adrenoceptors in a knock-in mouse that expressed a hemoagglutinin (HA) tag downstream of the α2A-adrenoceptor promoter. Although the α2A-adrenoceptor was often identified pre-synaptically, we observed co-localization of CB1r with α2-adrenoceptors post-synaptically in the same mPFC neurons. Finally, using receptor binding, we confirmed prior results showing that α2A-adrenoceptor is unchanged in mPFC following acute or chronic exposure to the synthetic cannabinoid receptor agonist, WIN 55,212-2, but is increased, following chronic treatment followed by a period of abstinence. Taken together, these data provide convergent lines of evidence indicating cannabinoid regulation of the cortical adrenergic system.
Department of Pharmacology and Physiology, College of Medicine, Drexel University Philadelphia, PA 19102, United States. Electronic address: Beverly.Reyes@drexelmed.edu.
B A S
BAS
Reyes
Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Campus Gualtar, 4710-057 Braga, Portugal.
A F
AF
Carvalho
Northwest Network for Mental Illness Research, Education, and Clinical Center, Veterans Administration Puget Sound Health Care System and Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, WA 98108, United States.
P
P
Szot
Center for Substance Abuse Research and Department of Anatomy and Cell Biology, Lewis Katz School of Medicine at Temple University, Philadelphia, PA 19140, United States.
D J
DJ
Kalamarides
Department of Cell, Development and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL 35294, United States.
Q
Q
Wang
Center for Substance Abuse Research and Department of Anatomy and Cell Biology, Lewis Katz School of Medicine at Temple University, Philadelphia, PA 19140, United States.
L G
LG
Kirby
Department of Pharmacology and Physiology, College of Medicine, Drexel University Philadelphia, PA 19102, United States.
E J
EJ
Van Bockstaele
D000818:Animals; D048588:Benzoxazines / Q000494:pharmacology; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D002186:Cannabinoids / Q000494:pharmacology; D008125:Locus Coeruleus / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D018345:Mice, Knockout; D009025:Morpholines / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism; D017397:Prefrontal Cortex / Q000187:drug effects* / Q000378:metabolism; D043882:Receptors, Cannabinoid / Q000172:deficiency / Q000378:metabolism*; D013569:Synapses / Q000187:drug effects / Q000378:metabolism
D048588:Benzoxazines; D002186:Cannabinoids; D009025:Morpholines; D009281:Naphthalenes; D043882:Receptors, Cannabinoid; C070417:(3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone; D009638:Norepinephrine
Cannabinoid receptor knock out mice; Cannabinoid receptor type 1; Locus coeruleus; Medial prefrontal cortex; Tyrosine hydroxylase; α2-Adrenoceptors