THE AMELIORATIVE EFFECTS OF THE AQUEOUS EXTRACT OF ROSEMARY AGAINST MONOSODIUM GLUTAMATE NEUROTOXICITY IN ADULT MALE ALBINO RATS: HISTOLOGICAL, ULTRASTRUCTURAL AND BIOCHEMICAL STUDIES

Hoda A. Mahran* and Samah M. Arisha

ABSTRACT

Background: monosodium glutamate (MSG) is a major flavor enhancer is still being used as food additive. Despite its taste stimulation and improved appetite enhancement, many reports indicated that MSG is toxic to human and experimental animals. Monosodium glutamate caused several pathological and biochemical changes in many tissues. Recently, several natural traditional plants are used against the toxicity of many chemicals and drugs. Rosemary (Rosmarinus officinalis), as a natural plant, is used as food additive which has many chemical components that can improve and/or prevent the toxic effects of MSG. Aim of the work: the present study was designed to investigate the ameliorative effect of the aqueous rosemary extract against MSG toxicity on cerebellar cortex of adult male albino rats. This will be monitored through histological, ultrastructural and biochemical studies. Materials and methods: thirty two adult male albino rats (Rattus norvegicus) were divided equally into four groups. Group 1: was considered as non-treated control. Group 2: animals were orally given the aqueous rosemary extract (ARE) (10ml/kg body weight/day) for six weeks. Group 3: animals were administered MSG only (4mg/kg body weight/day) for six weeks. Group 4: animals were given MSG and after 2 hours they were given ARE (with the same doses as in group two and three). Twenty four hours after the last dose, cerebella were removed and prepared for light and electron microscope studies. In addition, blood samples were collected and sera separated for biochemical studies. Results: histological observations: cerebellar cortex of animals administered MSG showed many pathological changes in the different layers. The outermost layer (molecular layer) of the cerebellar cortex was degenerated with vacuolated neuropil. The middle layer (Purkinje cell layer) appeared disorganized (lost its monolayer appearance) and contained degenerated Purkinje cells with pyknotic nuclei. In addition, the innermost layer (granular layer) contained some vacuolated granule cells. Ultrastructural observations: many alterations in the granule and Purkinje cells were seen. These cells appeared irregular with pyknotic nuclei and degenerated cytoplasmic organelles. Moreover, in the molecular layer, the myelin sheath of some axons of the nerve fibers appeared with completely splitting lamellae while others appeared with partially compact lamellae. The axoplasms were rarified with degenerated mitochondria. Animals treated with MSG and ARE revealed an obvious improvement of the previously observed pathological and ultrastructural changes. Biochemical results: monosodium glutamate treated rats showed a highly significant increase in serum malondialdehyde level (MDA) and highly significant decrease in catalase activity. Concerning lipid profile, animals administered MSG showed highly significant increase in the concentrations of total cholesterol, triglycerides and low-density lipoprotein (LDL) while high-density lipoprotein (HDL) showed highly significant decrease. On the other hand, animals administered MSG and ARE showed nearly normal levels of all the biochemical parameters. Conclusion: this study concluded that the aqueous rosemary extract ameliorated MSG neurotoxicity in adult male albino rats which may be attributed to its antioxidant and anti-inflammatory properties.

Keywords: Monosodium Glutamate, Rosemary Extract, Cerebellar Cortex, Histological, Ultrastructural, Biochemical.