title: Milk intake and survival in newborn cannabinoid CB1 receptor knockout mice: evidence for a "CB3" receptor.
abstract: Cannabinoids, whether plant-derived, synthetic or endogenous, have been shown to stimulate appetite in the adult organism. We have reported previously that cannabinoid receptors play a critical role during the early suckling period: The selective cannabinoid CB(1) receptor antagonist N-(piperidiny-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (SR141617A) permanently prevented milk ingestion in a dose-dependent manner, when administered to (Sabra, albino) mouse pups, within 1 day of birth. As a consequence, these pups died within the first week of life. We now generalize this finding to a different strain of mice (C57BL/6). Further, we show that cannabinoid CB(1) receptor blockade (20 mg/kg SR141716A) must occur within 24 h after birth as injection of SR141716A into 2- or 5-day-old pups had a much smaller effect or no effect at all, respectively. Cannabinoid CB(1) receptor knockout mice did not ingest milk on the first day of life, similarly to SR141716A-treated normal pups, as measured by the appearance of "milkbands". However, the knockout pups started to display milkbands from day 2 of life. Survival rates of cannabinoid CB(1) receptor knockout mice were affected significantly, but to a lesser extent than normal pups, by the administration of SR141716A. Daily administration of the endocannabinoid 2-arachidonoyl glycerol, or the synthetic agonists (R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-1-naphthalenylmethanone (WIN55,212-2, 5 mg/kg) or (-)-cis-3-[2-Hydroxy4-(1,1-dimethylheptyl) phenyl]-trans-4-(3-hydroxypropyl)cyclohexanol (CP55,940, 5 or 20 mg/kg) did not promote survival or weight gain in CB(1)(-/-) pups. Our data support previous evidence for a critical role of cannabinoid CB(1) receptors for the initiation of suckling. Further, the present observations support the existence of an unknown cannabinoid receptor, with partial control over milk ingestion in newborns. Our data also suggest that the CB(1)(-/-) neonates possess a compensatory mechanism which helps them overcome the lack of cannabinoid CB(1) receptors.
authors.affiliation: Department of Behavioral Sciences, College of Judea and Samaria, Ariel 44837, Israel. fride@research.yosh.ac.il
authors.forename: Ester
authors.initials: E
authors.lastname: Fride
authors.forename: Anat
authors.initials: A
authors.lastname: Foox
authors.forename: Elana
authors.initials: E
authors.lastname: Rosenberg
authors.forename: Moran
authors.initials: M
authors.lastname: Faigenboim
authors.forename: Vickey
authors.initials: V
authors.lastname: Cohen
authors.forename: Lena
authors.initials: L
authors.lastname: Barda
authors.forename: Hannah
authors.initials: H
authors.lastname: Blau
authors.forename: Raphael
authors.initials: R
authors.lastname: Mechoulam
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000833:Animals, Suckling; D001095:Arachidonic Acids; D001522:Behavior, Animal / Q000187:drug effects*; D048588:Benzoxazines; D063385:Cannabinoid Receptor Modulators; D003511:Cyclohexanols / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004435:Eating / Q000187:drug effects; D063388:Endocannabinoids; D005260:Female; D005989:Glycerides / Q000494:pharmacology; D007279:Injections, Subcutaneous; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008892:Milk; D009025:Morpholines / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D010880:Piperidines / Q000008:administration & dosage / Q000494:pharmacology; D011720:Pyrazoles / Q000008:administration & dosage / Q000494:pharmacology; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug / Q000819:agonists / Q000037:antagonists & inhibitors / Q000235:genetics*; D000077285:Rimonabant; D015996:Survival Rate; D013997:Time Factors
chemical_list: D001095:Arachidonic Acids; D048588:Benzoxazines; D063385:Cannabinoid Receptor Modulators; D003511:Cyclohexanols; D063388:Endocannabinoids; D005989:Glycerides; D009025:Morpholines; D009281:Naphthalenes; D010880:Piperidines; D011720:Pyrazoles; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug; C070417:(3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone; C054649:3-(2-hydroxy-4-(1,1-dimethylheptyl)phenyl)-4-(3-hydroxypropyl)cyclohexanol; C094503:glyceryl 2-arachidonate; D000077285:Rimonabant