Minocycline ameliorates anxiety-related self-grooming behaviors and alters hippocampal neuroinflammation, GABA and serum cholesterol levels in female Sprague-Dawley rats subjected to chronic unpredictable mild stress

Neuroinflammation induced by stress results in aberrant neurotransmission and dyslipidemia, which can trigger depression- and anxiety-like behaviors. Gamma-aminobutyric acid (GABA) and cholesterol play a crucial role in anxiety-like states, including self-grooming - a common stress-evoked rodent behavior. However, the interaction between neuroinflammation, GABA and cholesterol under stress, and their effects on grooming, remain unclear. Here, we utilize the chronic unpredictable mild stress (CUMS) rat cohort used previously in our Zhang et al. (2019) study, to examine whether CUMS affects grooming behavior, and whether minocycline, a microglia antagonist, can correct these behavioral deficits, accompanied by altering hippocampal neuroinflammation, GABA and serum cholesterol levels. Female Sprague-Dawley rats underwent a 6-week CUMS and received daily minocycline (40 mg/kg, i.p.) during this period, followed by behavioral testing in the open field test. Serum cholesterol, inflammatory cytokines and GABA levels in hippocampus were assayed by ELISA. CUMS significantly decreased locomotion, rearing, central zone entries and time spent in the open field center compared to unstressed controls. CUMS also strongly affected self-grooming behaviors, increasing the frequency of grooming episodes, the number of transitions, interruptions and individual elements of various grooming phases. However, these CUMS-induced behavioral abnormalities were corrected by minocycline. Likewise, CUMS elevated total serum cholesterol and lowered serum high-density lipoprotein cholesterol, whereas minocycline ameliorated these responses. CUMS also lowered hippocampal GABA, whereas minocycline normalized CUMS-induced GABA in the hippocampus. We also found significant correlations between neuroinflammation and GABA, neuroinflammation and cholesterol, GABA and grooming, as well as cholesterol and grooming measures, further implicating stress-evoked neuroinflammation, GABA and cholesterol in the regulation of complex rodent behaviors. In summary, minocycline ameliorated CUMS-induced aberrant self-grooming behaviors in rats by altering hippocampal neuroinflammation, GABA and serum cholesterol levels.