title: Spontaneous locomotor activity correlates with the degranulation of mast cells in the meninges rather than in the thalamus: disruptive effect of cocaine.
abstract: Mast cells are located in the central nervous system (CNS) of many mammals and stress induces their degranulation. We postulated that mast cells are associated with wakefulness and stimulatory tone in the CNS, as reflected by spontaneous motor activity. Because stress also precipitates drug-seeking behavior in cocaine addicts, we also postulated that cocaine manifests its effects through this relationship. We investigated the influence of single and repeated injections of cocaine on circulating corticosterone, motor activity and degranulation of mast cells in both the thalamus and meninges of mice. Mice were subjected to 5 consecutive days of cocaine or saline followed by a single injection of cocaine or saline 11 days later. Spontaneous locomotor activity was measure for 1h after the final injection before death. Neither a single injection nor prior treatment with cocaine increased motor activity compared to saline-injected controls, however, repeated administration of cocaine induced a significant sensitization to its behavioral effect when delivered 11 days later. In mice that received only saline, motor activity correlated positively with mast cell degranulation in the meninges but not in the thalamus. Cocaine, regardless of the treatment schedule, disrupted this correlation. The concentration of corticosterone did not differ amongst groups and did not correlate with either behavior or mast cell parameters in any group. The correlation between behavioral activity and the mast cell degranulation in the meninges suggests that these parameters are linked. The disruptive effect of cocaine on this relationship indicates a role downstream from mast cells in the regulation of motor activity.
authors.affiliation: Department of Veterinary and Biomedical Sciences, University of Minnesota, 1988 Fitch Avenue, Room 295, St. Paul, MN 55108, USA. larso011@umn.edu
authors.forename: Alice A
authors.initials: AA
authors.lastname: Larson
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Thomas
authors.forename: Alex
authors.initials: A
authors.lastname: McElhose
authors.forename: Katalin J
authors.initials: KJ
authors.lastname: Kovács
mesh_terms: D017109:Akathisia, Drug-Induced / Q000473:pathology* / Q000503:physiopathology; D000818:Animals; D015550:Cell Degranulation / Q000187:drug effects* / Q000502:physiology; D003042:Cocaine / Q000633:toxicity*; D019970:Cocaine-Related Disorders / Q000473:pathology* / Q000503:physiopathology; D004195:Disease Models, Animal; D018765:Dopamine Uptake Inhibitors / Q000633:toxicity; D004334:Drug Administration Schedule; D008297:Male; D008407:Mast Cells / Q000187:drug effects* / Q000378:metabolism; D008578:Meninges / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D013315:Stress, Psychological / Q000473:pathology / Q000503:physiopathology
chemical_list: D018765:Dopamine Uptake Inhibitors; D003042:Cocaine