Regular chow

All animal use protocols were approved by the Institutional Animal Care and Use Committee at the University of Alabama at Birmingham and were consistent with the Guide for the Care and Use of Laboratory Animals; Eighth Edition (NIH Academies Press, 2011). All mice used were from the C57BL/6 background, housed in the same vivarium at constant humidity (60 ± 5%) and temperature (24 ± 1°C) with a 12 h light cycle (6 a.m.−6 p.m.), and maintained ad libitum on sterile water and regular chow (Harlan Teklad). Mice were at least 8 weeks old when bone marrow, spleens, and lymph nodes were harvested and both sexes were used. Where indicated, bone marrow (BM) was harvested from FcγRIIB deficient mice (FcγRIIB^−/−; B6.129S4-Fcgr2b^tm1TtK N12, Taconic Farms model 580) that lack functional expression of the gene encoding the α-chain of mouse FcγRIIB (24 (link)).

For locomotor activity and ex vivo neurochemistry studies, a total number of 152 male NMRI mice weighing 18–25 g at arrival were supplied by Janvier (France). For in vivo microdialysis, a total number of 54 male Wistar rats weighing 260–280 g at arrival were supplied by Envigo (Netherlands). Mice were housed eight to a cage whereas rats were housed four to a cage prior to surgery and single-housed after surgery, under controlled environmental conditions comprising constant room temperature of 20–22 °C, humidity of 50–65% and regular light-dark conditions with lights on at 07:00 a.m. and off at 07:00 p.m. Before any experimental procedures were initiated, animals were allowed at least one week of acclimatization to the facilities. All animals had access to regular chow (Harlan Teklad, England) and tap water ad libitum. The experiments were approved by the Ethics Committee for Animal Experiments, Gothenburg, Sweden.

Male and female Sprague Dawley rats (Charles River) were housed doubly in individually ventilated cages (Techniplast) with regular enrichment, on a reversed light cycle 12/12 h cycle (lights off at 7 A.M.) until the age of approximately two to four months, and then singly housed thereafter. Rats were fed regular chow (Teklad2018); however, both male and female rats were placed on a modest food restriction schedule at two to three months of age, to maintain a healthy aging weight profile and to reduce obesity related illnesses in old age (Hubert et al., 2000 (link)). Rats were fed between 8:30 and 10:30 A.M. daily and received an amount of food that was 75% (g) of the average age-dependent and sex-dependent ad libitum consumption (Hubert et al., 2000 (link)). Water was available ad libitum. The average mass at the time of electrophysiological recording in the five- to nine-month-old rats; females 366.33 ± 27.45 g and males 674.8 ± 38.89 g, and for 18- to 20-month-old rats; females 456.00 ± 81.82 g and males, 748.80 ± 71.11 g.
All experimental procedures occurred within the dark phase of the animals’ light cycle (9 A.M. to 5 P.M.) and were performed in accordance with the Canadian Council of Animal Care (CCAC) guidelines and approved by the Memorial University of Newfoundland and Labrador Institutional Animal Care Committee.