Journal of Ethnopharmacology 79 (2002) 13 – 16 Effect of Zizyphus spina -christi Willd aqueous extract on the central nervous system in mice B. Adzu, S. Amos, S. Dzarma, C. Wambebe, K. Gamaniel * Department of Pharmacology and Toxicology, National Institute for Pharmaceutical Research and Deelopment, P. M. B. 21, Garki, Abuja, Nigeria Accepted 17 July 2001 Abstract The effects of the aqueous extract of Zizypus spina -christi Willd root bark against exploratory behaviour, spontaneous motor activity (SMA), motor coordination (Rota-rod performance) and pentobarbital-induced hypnosis were investigated in mice. The extract induced a significant (P 0.05) dose-dependent reduction in exploratory behaviour and SMA when administered orally. It also prolonged pentobarbital sleeping time but failed to inhibit motor coordination (rota-rod performance) in the experimental mice. These results suggest that the extract contained some constituents that depress the central nervous system, which may not be due to neuromuscular blockade. © 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Exploratory behaviour; Spontaneous motor activity; Motor coordination; Pentobarbital sleep www.elsevier.com/locate/jethpharm 1. Introduction The plant Zizyphus spina -christi Willd is of the Rhamnaceae family, and it grows wild in northern Nigeria. It is characterised by thorny branches used as a hedge to form defensive enclosure. The fruit have sweet edible pulp. Medicinally, the leaves are applied locally to sores (Dalziel, 1937) as wound powder and antiseptics (Fleurentin and Pelt, 1982) and was reported to exhibit hypoglycemic activity against streptozotocin- diabetics rats (Glombitza et al., 1994) and antibacterial efficacy against Gram-positive strains (Ali et al., 2001), while its root bark is used in folk medicine as a remedy against pain. Major chemical constituents of the plant had been investigated and reported (Ikram and Tomlin- son, 1976; Mahran et al., 1996). Our previous studies on the aqueous extract of the root bark revealed the presence of saponins, tannins and glycosides. The symptoms of toxicity of the extract include severe depression and dyspnoea. The extract also exhibits anti-nociceptive properties with both pe- ripheral and central aspects (Adzu et al., 2001). In this study, we evaluated the nature of the central effects of the extract by measuring the exploratory behaviour, spontaneous motor activity (SMA), rota-rod (a tread mill) performance and pentobarbital sleeping time in mice. 2. Material and methods 2.1. Plant material Roots of the plant were collected by Achaba Lugudu (a herbalist) at Midlu – Vapura, Adamawa State, Nige- ria, on 20th February 2001. The identify of the plant was authenticated at the Department of Medicinal Plant Research and Traditional Medicine, National Institute for Pharmaceutical Research and Develop- ment (NIPRD) Abuja, Nigeria. A voucher specimen of the plant was deposited at the Taxonomic Unit of the Department (No. 4108). The root bark was separated and cleaned, then dried under shade. The dried material was powdered and 100 g were macerated in 1 l of cold distilled water for 24 h with occasional shaking, then filtered through Whatman No. 1 filter paper and freeze- dried using Lyovac, GT2 (Germany). This gave a yield of 5.9 % w/w and was dissolved in double distilled water at the desired concentration just before use. * Corresponding author. Tel.: +234-9-5239089; fax: +234-9- 5231043. E-mail address: ksgama@yahoo.com (K. Gamaniel). 0378-8741/02/$ - see front matter © 2002 Elsevier Science Ireland Ltd. All rights reserved. PII:S0378-8741(01)00348-8