Excitatory actions of propofol and ketamine in the snail Lymnaea stagnalis

This study compares the actions of the intravenous anaesthetics propofol an d ketamine on animal behaviour and neuronal activity in the snail Lymnaea s tagnalis, particularly in relation to excitatory effects observed clinicall y. When injected into the whole animal, neither agent induced total anaesth esia. Rather, behavioural activity was enhanced by propofol (10(-5) M) and ketamine (10(-7) M), indicating excitatory effects. When superfused over th e isolated central nervous system (CNS), differential effects were produced in two identified neurons, right pedal dorsal 1 (RPeD1) and visceral dorsa l 4 (VD4). Resting membrane properties were largely unaffected. However, sp ike after hyperpolarisation was significantly reduced in RPeD1, but not VD4 , with some evidence of increased excitability. In addition, an intrinsic b ursting property (post-stimulus burst) in VD4 was altered by propofol (10(- 7) M). The results suggest significant excitatory components in the actions of some intravenous anaesthetics, as well as a potential role in modifying excitation and bursting mechanisms in the CNS. (C) 2000 Elsevier Science I nc. All rights reserved.