Pharmacological, electrophysiological and toxicity studies of Limacia scanden Lour. (Menispermaceae).
Pharmacological studies showed that Limacia scanden Lour. extracts have sympathomimetic activities similar to noradrenaline (NA). A crude extract of Limacia scanden injected intravenously as a single bolus induced a dose-dependent increase in arterial blood pressure in anaesthetized rats and cats. Pretreatment with a non-specific alpha blocker phentolamine (10(-5) M) blocked this effect, whereas the beta blocker propanolol (10(-5) M) did not. The extract also reduced intestinal motility and this response could be blocked by pretreatment with phentolamine (10(-5) M) and specific alpha1-blocker, prazosin (10(-5) M). In superfused rabbit aorta preparations, it induced an increase in contractions. This effect was blocked by pretreatment with prazosin (10(-5) M), whereas the alpha2-blocker yohimbine (10(-5) M) had only a slight effect. The effects of NA on superfused aorta strip contraction were similar to extract. Toxic symptoms were manifested in less than 5 min when the mice were given 465 mg/kg of extract intraperitoneally. Physiological and behavioural changes observed in dying mice implicated serious malfunctioning of the autonomic nervous system and motor activity. Electrophysiological studies on the tonically autoactive neuron (TAN) of the snail Achantina fulica Férussac revealed that crude extract of Limacia scanden induced excitatory responses which were similar to those of serotonin (5-HT) stimulation. Studies with different ionic compositions of the bathing saline revealed that this excitatory effect of Limacia scanden could be attributed either to release of endogenous serotonin or inhibition of 5-HT reuptake in the CNS. This observation could tentatively be used to provide the framework towards elucidating the mechanism and rationale for the use of this plant in traditional medicine in the treatment of depression and affective disorders.
Kim Kah Hwi
Department of Physiology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia.
Wong Bee Lay
D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects; D002415:Cats; D005769:Gastrointestinal Motility / Q000187:drug effects; D066298:In Vitro Techniques; D007928:Lethal Dose 50; D009682:Magnetic Resonance Spectroscopy; D008564:Membrane Potentials / Q000187:drug effects*; D051379:Mice; D009119:Muscle Contraction / Q000187:drug effects; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology* / Q000633:toxicity; D010946:Plants, Medicinal / Q000737:chemistry*; D011817:Rabbits; D051381:Rats
D010936:Plant Extracts