Nicotine

B. malayi and Brugia pahangi adults extracted from the Meriones unguiculatus infection system (NIH/NIAID Filariasis Research Reagent Resource Center) (105 (link)) were maintained in daily changes of RPMI 1640 medium with l-glutamine (Sigma-Aldrich) supplemented with fetal bovine serum (FBS) (10%, vol/vol; Fisher Scientific) and penicillin-streptomycin (0.1 mg/mL; Gibco) at 37°C with 5% CO₂ unless otherwise specified. Brugia microfilariae isolated from the same system were maintained in RPMI 1640 medium supplemented with l-glutamine (Sigma-Aldrich) and penicillin-streptomycin (0.1 mg/mL; Gibco) at 37°C with 5% CO₂ unless otherwise specified.
The chemicals used in the assays included serotonin (catalog number AAB2126306; Fisher Scientific), arecoline (catalog number AC250130050; Fisher Scientific), atropine (catalog number sc-252392; Santa Cruz Biotechnology), nicotine (catalog number sc-482740; Santa Cruz Biotechnology), levamisole (catalog number TCL0231-1G; VWR), carbachol (catalog number sc-202092; Santa Cruz Biotechnology), acetylcholine (catalog number AC159170050; Fisher Scientific), oxotremorine M (catalog number sc-203656; Santa Cruz Biotechnology), and aldicarb (catalog number sc-254939; Santa Cruz Biotechnology).

The animals were randomly divided into six groups with 12 mice in each; in the control group, mice did not receive any injection or treatment. In the DGal-induced aging group, for modeling of brain aging, mice were injected with DGal (500 mg/kg s.c. for 6 weeks; Sigma-Aldrich, St. Louis, MO, USA). Separate groups of DGal-injected mice received either NS or nicotine (Santa Cruz Biotechnology, Santa Cruz, CA, USA) through either s.c. (0.1, 0.5 and 1 mg/kg) or i.n. (0.1 mg/kg) routes for 6 weeks. For i.n. administration of nicotine drops containing 5–6 μl were administered through nasal mucosa with alternation between left and right nares for 2 min to reach the total desired volume (Pourmemar et al., 2017 (link)). At the end of the treatment administration period, the behavioral tests and biochemical analyses were performed (Figure 1). All tests were performed by an experimenter that was unaware of the identity of experimentations. All solutions were freshly prepared on the day of experimentation by dissolving drugs in NS (0.9% NaCl). All injections had a volume of 8 ml/kg body weight.