Altered CB receptor-signaling in prefrontal cortex from an animal model of depression is reversed by chronic fluoxetine.
Bilateral olfactory bulbectomy in the rat (OBX) induces behavioral, neurochemical, and structural abnormalities similar to those observed in human depression that are normalized after chronic, but not acute, treatment with antidepressants. In our study, OBX animals exhibited significant increases in both CB(1) receptor density ([(3)H]CP55490 binding) and functionality (stimulation of [(35)S]GTPgammaS binding by the cannabinoid (CB) agonist WIN 55212-2) at the prefrontal cortex (PFC). After chronic treatment with fluoxetine (10 mg/kg/day, 14 days, s.c.), OBX-induced hyperactivity in the open-field test was fully abolished. Interestingly, chronic fluoxetine fully reversed the enhanced CB(1)-receptor signaling in PFC observed following OBX. The CB agonist Delta(9)-tetrahydrocannabinol (5 mg/kg, i.p., 1 day) did not produce any behavioral effect in sham-operated animals but returned locomotor activity to control values in OBX rats. As both acute administration of Delta(9)-tetrahydrocannabinol and chronic fluoxetine elicited a similar behavioral effect in the OBX rat, it is not unlikely that the regionally selective enhancement of CB(1) receptor-signaling in the PFC could be related with the altered OBX behavior. Our findings reinforce the utility of this animal model to further investigating the implication of the endocannabinoid system in the modulation of emotional processes and its potential role in the adaptive responses to chronic antidepressants.
Rodríguez-Gaztelumendi
Antonio
A
Departamento de Fisiología y Farmacología, Universidad de Cantabria. Instituto de Biomedicina y Biotecnología de Cantabria (CSIC-UC-IDICAN), Santander, Instituto de Salud Carlos III, Spain.
Rojo
M Luisa
ML
Pazos
Angel
A
Díaz
Alvaro
A
D000818:Animals; D018687:Antidepressive Agents, Second-Generation / Q000008:administration & dosage*; D001345:Autoradiography; D003511:Cyclohexanols / Q000378:metabolism; D003863:Depression / Q000188:drug therapy / Q000473:pathology*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D013759:Dronabinol / Q000031:analogs & derivatives / Q000494:pharmacology; D004334:Drug Administration Schedule; D005106:Exploratory Behavior / Q000187:drug effects; D005473:Fluoxetine / Q000008:administration & dosage*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D007166:Immunosuppressive Agents / Q000378:metabolism; D007554:Isotopes / Q000378:metabolism; D008297:Male; D009830:Olfactory Bulb / Q000293:injuries; D017397:Prefrontal Cortex / Q000187:drug effects* / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D043884:Receptor, Cannabinoid, CB1 / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D013997:Time Factors
D018687:Antidepressive Agents, Second-Generation; D003511:Cyclohexanols; D007166:Immunosuppressive Agents; D007554:Isotopes; D043884:Receptor, Cannabinoid, CB1; D005473:Fluoxetine; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C072823:delta9-tetrahydrocannabinol hemisuccinate; D013759:Dronabinol; C054649:3-(2-hydroxy-4-(1,1-dimethylheptyl)phenyl)-4-(3-hydroxypropyl)cyclohexanol