Non-linear dose effect relationship in anxiolytic and nootropic activity of lithium carbonate and Nardostachys jatamansi in rats

Abstract

There is increasing use of traditional remedies with modern medicine. It needs to be evaluated whether such integration will be useful or otherwise. We studied interaction between lithium carbonate and Nardostachys jatamansi extract (NJE), given separately and together, both on acute administration and repeated administration in rats with respect to anxiolytic and nootropic activities. Acute administration of lithium carbonate NJE (100 and 200 mg/kg i. p.) given separately, significantly increased time spent in the open arm indicating reduced anxiety. Lithium carbonate (10 mg/kg i. p.) significantly reduced anxiolytic activity of NJE. Rats receiving lithium carbonate (10 mg/kg i.p. for 21 days) and NJE (100 and 200 mg/kg) acutely on 21st day, showed significantly diminished anxiolytic activity of NJE. NJE (100 and 200 mg/kg) used alone, exhibited nootropic activity in the elevated plus maze and object recognition test. In the elevated plus maze, acute administration of lithium carbonate (10 mg/kg) and NJE (100 mg/kg) showed significant improvement in nootropic activity and diminished nootropic response to NJE (200 mg/kg). Similar biphasic effect was observed when rats received lithium carbonate for 21 days and NJE on 21st day. In the object recognition test, acute administration of lithium carbonate and NJE improved nootropic activity but in rats receiving lithium for 21 days, NJE (100 mg/kg) improved and (200 mg/kg) reduced nootropic activity. Thus there is a non-linear dose effect relationship between lithium carbonate and NJE suggesting necessity of careful selection of doses to avoid loss of activity.