TNF and serum lipopolysaccharide activity: However, nicotine appeared to be protective to heart abnormalities because LPS-evoked hypotensive and tachycardic responses, reductions in time-domain indices of heart rate variability and spectral measure of cardiac sympathovagal balance, and upregulation of serum TNF-α were reversed by nicotine (25, 50, and 100 μg/kg, i.v.)via α7 and α4β2 nAChRs in male Wistar rats with endotoxemia (126).