NEUROPHARMACOLOGICAL PROPERTIES OF ETHANOL EXTRACT OF THE LEAVES OF Olax subscorpioidea OLIV. (OLACACEAE) IN MICE

Abstract

Olax subscorpioidea is used in the management of mental illness, fever and pain in ethnomedicine. However, there is scanty information on the neuropharmacological activities that supports its use. The study was designed to investigate the neuropharmacological properties of Ethanol Extract of Olax subscorpioidea Leaves (EEOSL) in male mice.

Air-dried leaves (150 g) were pulverized and soaked in 50% ethanol (1.5 L) for 48 hours. The filtrate was concentrated and evaporated to dryness (8.7 g). Twenty-five Swiss male albino mice (20-22 g) were allotted into five treatment groups viz: control (distilled water), and EEOSL (3.1, 6.3, 12.5, 25 mg/kg) with five animals in each group. They were pretreated thirty minutes intraperitoneally (i.p.), before neurobehavioural effects of EEOSL on novelty-induced behaviours (rearing and grooming) and frequency of head dips were investigated using open-field and hole-board tests respectively. Another twenty male mice (22-25 g) divided into four treatment groups: control (distilled water) and EEOSL (12.5, 25, 50 mg/kg). Thirty minutes after i.p. treatment, pentobarbitone-induced sleeping time was investigated. For analgesic study, eighty male mice (22-25 g) were allocated into four treatment groups: control (distilled water), and EEOSL (12.5, 25, 50 mg/kg) with five animals in each group. Thirty minutes after i.p. treatment they were subjected to acetic-acid induced writhing, formalin, tail immersion and hot plate tests. Similarly, for antidepressant study, another set of eighty male mice (22-25 g) were randomly allotted into four treatment groups: control (distilled water), and EEOSL (6.3, 12.5, 25 mg/kg) with five animals in each group. Thirty minutes after i.p. treatment, animals were subjected to despair, tail suspension, reserpine-induced depression, and yohimbine lethality tests. Data were analysed using descriptive statistics and ANOVA at p = 0.05.

The EEOSL (3.1, 6.3, 12.5, 25 mg/kg) significantly inhibited rearing (99.8+2.8, 76.2+2.9, 37.4+1.2, 5.8+0.8) and grooming (48.0+3.6, 33.8+2.9, 25.4+1.6, 7.6+0.8) compared with controls (185.8+5.1; 63.8+4.3) respectively. Treatment with EEOSL (3.125, 6.25, 12.5, 25 mg/kg) significantly decreased the frequency of head dips on hole-board (10.6+1.9, 8.8+1.2, 7.2+0.9, 6.0+1.1) compared with control (27.8+1.5). The EEOSL (12.5, 25, 50 mg/kg) significantly prolonged pentobarbitone-induced sleeping time (43.0+1.4, 51.0+1.2, 61.0+1.8) compared with control (31.0+0.7). The EEOSL (12.5, 25, 50 mg/kg) significantly inhibited acetic acid-induced pain by 66.9%, 72.7% and 81.5% respectively. In formalin test, EESOL (12.5, 25, 50 mg/kg) inhibited neurogenic (41.1%, 63.1%, 66.0%) and inflammatory (57.1%, 75.3%, 79.4%) pains. Reaction times were prolonged only by EEOSL (50 mg/kg) in hot plate (0.9+0.1) and tail immersion (2.1+0.2) compared with controls (0.6+0.1; 0.5+0.0) respectively. The EEOSL (6.3, 12.5 mg/kg) significantly reduced immobility periods in despair (124.2+4.5, 85.2+6.0) and tail suspension tests (110.4+6.8, 68.0+15.9) compared with controls (190.2+15.3; 155.6+8.9) respectively. In reserpine-induced depression, EEOSL (6.3, 12.5, 25 mg/kg) reduced significantly the feacal matter (2.4+0.9, 1.2+0.6, 1.2+0.4) compared with control (8.2+0.9). However, EEOSL did not potentiate yohimbine-induced lethality.

Olax subscorpioidea possessed sedative, antidepressant and analgesic properties. These therefore support its traditional claims in the management of mental illness and pain. Keywords: Olax subscorpioidea, Neurobehavioural, Analgesic, Antidepressant. Word count: 479