In search of novel potential drug candidates that could be used as treatments or prophylactics for memory impairment, an aporphine alkaloid magnoflorine (MAG) isolated from the root of Berberis vulgaris was proven to exhibit beneficial anti-amnestic properties. Its effects on immunoreactivity to parvalbumin in the mouse hippocampus were assessed together with a study on its safety and concentration in the brain and plasma. For this purpose, four experimental groups were created: the MAG10 group—treated with 10 mg MAG/kg b.w. i.p., the MAG20 group—treated with 20 mg MAG/kg b.w. i.p., the MAG50 group—treated with 50 mg MAG/kg b.w. i.p., and a control group—injected with saline i.p. at a volume corresponding to their weight. Our results indicated that the hippocampal fields CA1–CA3 were characterized by an elevated number of parvalbumin-immunoreactive neurons (PV-IR) and nerve fibers in mice at the doses of 10 and 20 mg/kg b.w. (i.p.). No significant changes to the levels of IL-1β, IL-6 or TNF-α were observed for the above two doses; however, the administration of 50 mg/kg b.w. i.p. caused a statistically significant elevation of IL-6, IL-1beta plasma levels and an insignificant raise in the TNF-alpha value. The HPLC–MS analysis showed that the alkaloid’s content in the brain structures in the group treated with 50 mg/kg b.w. did not increase proportionally with the administered dose. The obtained results show that MAG is able to influence the immunoreactivity to PV-IR in hippocampal neurons and might act as a neuroprotective compound.