Journal of Ethnopharmacology 134 (2011) 55–61 Contents lists available at ScienceDirect Journal of Ethnopharmacology journal homepage: www.elsevier.com/locate/jethpharm Bacopa monniera leaf extract up-regulates tryptophan hydroxylase (TPH2) and serotonin transporter (SERT) expression: Implications in memory formation Prisila Dulcy Charles a , Ganesh Ambigapathy a , Pitchairaj Geraldine a , Mohammad Abdulkadar Akbarsha b , Koilmani Emmanuvel Rajan a,∗ a Department of Animal Science, School of Life Sciences, Bharathidasan University, Palkalaiperur, Tiruchirappalli 620024, Tamil Nadu, India b Gandhi-Gruber-Doerenkamp Center, Bharathidasan University, Tiruchirappalli 620024, India article info Article history: Received 28 January 2010 Received in revised form 25 October 2010 Accepted 22 November 2010 Available online 1 December 2010 Keywords: Bacopa monniera Learning and memory Serotonin Serotonin transporter Tryptophan hydroxylase abstract Aim of the study: To examine the effect of Bacopa monniera leaf ethanolic extract (BMEE) on the seroton- ergic system of postnatal rats with reference to learning and memory. Materials and methods: From postnatal day (PND)-15–29, rats were treated with BMEE (40 mg/kg BW + 0.5% gum acacia) by oral gavage. Behavioural tests (Y-maze, hole-board and passive avoidance) were used to evaluate their learning (PND-32–37) and retention of memory (PND-47–53). Effect of BMEE on neurotransmitter system was analyzed by ELISA and semi-quantitative polymerase chain reaction (PCR). Results: Oral administration of BMEE improved learning and retention of memory significantly in all behavioural tasks. Following BMEE treatment, the level of serotonin (5-HT) increased while dopamine (DA) decreased significantly. We also found variation in the level of acetylcholine (ACh). However, no significant changes were observed in the level of ACh and glutamate (Glu). The level of 5-HT was significantly elevated up to PND-37 and was then restored to normal level on PND-53. Interestingly, concomitant up-regulation was recorded in the mRNA expression of serotonin synthesizing enzyme tryptophan hydroxylase-2 (TPH2) and serotonin transporter (SERT) on PND-29 and PND-37, which was restored on PND-53. Conclusions: The results suggest that BMEE treatment significantly enhances the learning and retention of memory in postnatal rats possibly through regulating the expression of TPH2, 5-HT metabolism and transport. © 2010 Elsevier Ireland Ltd. All rights reserved. 1. Introduction Neurotransmitters such as dopamine (DA), serotonin [5- hydroxytryptamine (5-HT)] and norepinephrine (NE) are involved in the basic physiological, behavioural and endocrine functions (Greengard, 2001). Studies have correlated the memory perfor- mance with the systems extracellular 5-HT level, and depletion of tryptophan could affect the memory formation (van der Veen and Evers, 2006; Karakuyu et al., 2007). Biosynthesis of 5-HT is regulated by the rate-limiting enzyme tryptophan hydroxylase (TPH), the elevation of its mRNA expression has been reported to enhance TPH activity and 5-HT synthesis (Chamas et al., 1999; Kim et al., 2002). 5-HT is synthesized within 5-HT neuronal cell bod- ies, most of which are immunoreactive for serotonin transporter (SERT) (Fujita et al., 1993). Clearance of synaptic and extra-synaptic 5-HT is the principal function of SERT; altered SERT expression ∗ Corresponding author. Tel.: +91 431 2407040; fax: +91 431 2407045. E-mail address: emmanuvel1972@yahoo.com (K.E. Rajan). has been implicated in multiple forms of psychological disorders (Zhao et al., 2006). Several studies have tested the in vivo efficacy of plant extracts to identify biologically active compounds that could improve the mental function and learning ability (Khalifa, 2001; Rai et al., 2001; Das et al., 2002; Mohandas Rao et al., 2005; Kimani and Nyongesa, 2008). Bacopa monniera L. (Family: Scrophulariaceae) has been com- monly used in Indian traditional system of Ayurvedic medicine for improvement of memory deficit (Russo and Borrelli, 2005). The ethanolic extract of its leaf contains various active alkaloids such as nicotine, brahmine and herpestine, and triterpenoid saponins such as bacoside A and B (Chatterji et al., 1963, 1965; Kulshreshtha and Rastogi, 1973, 1974; Chandel et al., 1977). Later, several other saponin compounds such as bacopaside I, II, III, IV and V were identified (Chakravarty et al., 2001, 2003). Treatment of the leaf extract of Bacopa monniera alleviating several aspects of learning and mental function (Singh and Dhawan, 1982, 1997; Vollala et al., 2010), by modulating the levels of monoamine like noradrenaline (NA), DA and 5-HT at different regions of brain (Sheikh et al., 2007). It has also been reported to alter the glutamate receptor binding 0378-8741/$ – see front matter © 2010 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.jep.2010.11.045