Chronic cannabinoid exposure reduces phencyclidine-induced schizophrenia-like positive symptoms in adult rats.
BACKGROUND
Chronic cannabis use can induce psychotic states that resemble schizophrenia. Yet, schizophrenic patients often smoke cannabis as a form of self-medication to counter the aversive symptoms of schizophrenia. We recently demonstrated an ameliorating effect of cannabinoid self-administration (SA) on negative and cognitive schizophrenia-like symptoms induced experimentally by the non-competitive N-methyl-D-aspartate receptor antagonist phencyclidine (PCP). Whether cannabinoid SA alleviates or exacerbates schizophrenia-like positive symptoms is still unclear.


OBJECTIVE
This follow-up study aimed to evaluate the effect of self-administered cannabinoid on PCP-induced schizotypic positive symptoms in adult rats.


METHODS
Male rats were trained to self-administer either the cannabinoid CB1 receptor agonist WIN 55,212-2 (WIN; 12.5 μg/kg/infusion) or its vehicle (Veh) intravenously. The effects of acute and chronic intermittent intraperitoneal administration of PCP (2.5 mg/kg) on motor parameters were then tested in Veh-SA and WIN-SA.


RESULTS
Cannabinoid SA significantly attenuated the psychotomimetic effects of PCP exposure observed in control rats. Following acute PCP administration, WIN-SA animals displayed more frequent rearing and lower anxiety-like profile than Veh-SA rats. WIN-SA rats also exhibited lower behavioural sensitisation to chronic PCP treatment as demonstrated by reduced hyperlocomotion in response to an acute PCP challenge. In addition, parallel experiments performed in experimenter-administered rats that received WIN at comparable SA doses confirmed the ameliorating effects of cannabinoid exposure on PCP-induced schizotypic behaviours, indicating that motivational effects were not responsible for the ameliorative effects of cannabinoids.


CONCLUSIONS
Our results indicate that cannabis may exert protective effects on positive schizotypic symptoms in adult animals such as hypermotility and anxiety state.
CNR Neuroscience Institute, National Research Council, Monserrato (Cagliari), Italy.
Maria Sabrina
MS
Spano
Liana
L
Fattore
Francesca
F
Cadeddu
Walter
W
Fratta
Paola
P
Fadda
D000818:Animals; D001007:Anxiety / Q000139:chemically induced / Q000517:prevention & control; D001522:Behavior, Animal / Q000187:drug effects*; D048588:Benzoxazines / Q000008:administration & dosage / Q000627:therapeutic use; D063386:Cannabinoid Receptor Agonists / Q000008:administration & dosage / Q000627:therapeutic use; D002186:Cannabinoids / Q000008:administration & dosage / Q000627:therapeutic use*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D006213:Hallucinogens / Q000633:toxicity*; D007275:Injections, Intravenous; D008297:Male; D009025:Morpholines / Q000008:administration & dosage / Q000627:therapeutic use; D009043:Motor Activity / Q000187:drug effects; D009281:Naphthalenes / Q000008:administration & dosage / Q000627:therapeutic use; D010622:Phencyclidine / Q000633:toxicity*; D051381:Rats; D011919:Rats, Inbred Strains; D012559:Schizophrenia / Q000139:chemically induced / Q000517:prevention & control*; D012565:Schizophrenic Psychology; D012646:Self Administration
D048588:Benzoxazines; D063386:Cannabinoid Receptor Agonists; D002186:Cannabinoids; D006213:Hallucinogens; D009025:Morpholines; D009281:Naphthalenes; C070417:(3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone; D010622:Phencyclidine