CC BY
429th multidisciplinary international
Conference of Biological Psychiatry
«Stress and Behavior»
Proceedings of the 9th International Multidisciplinary Conference «Stress and behavior» Saint-Petersburg, Russia, 16-19 May 2005 Editor: Allan V. Kalueff, PhD
CONFERENCE ABSTRACTS 3. EPILEPSY
EFFECTS OF HSP70 ON NMDA-INDUCED SEIZURE IN RATS
Iu.F. Pastukhov, T.G. Komarova, L.E. Nitsinskaya, I.V. Ekimova Sechenov Institute of Evolutionary Physiology and Biochemistry RAS, St.-Petersburg, Russia
Increased expression of the heat shock protein-70 (HSP70) in the brain is observed during seizures induced by systemic administration of NMDA-receptor agonists and other chemoconvulsants [Ferrer, 2002]. HSP70 was able to bind to hydrophobic sites of signal peptide and participate in cell signaling [Beere et al., 2000; Margulis, Gushova, 2000]. Hyperthermia-induced HSP70 is associated with pre- and postsynaptic elements, including the postsynaptic density, in the mammalian brain tissue [Bechtold et al., 2000]. Using a medullary slice preparation from neonatal mouse, J.D. Kelty et al. [2002] demonstrated that thermal preconditioning and exogenous HSP70 exerts a protective effect on the heat stress-induced release of such neurotransmitters as GABA, glutamate, and glycine. In addition, exogenous HSP70 is reported to possess a hypnosedative activity. Microinjections of HSP70 into 3-d ventricle led to an increase in sleep and a decrease in muscle tone and brain temperature [Pastukhov et al., 2004]. The aim of this study is to examine our hypothesis whether HSP70 may act on neurotoxic effect of NMDA receptor activity, and alter the severity of NMDA-induced seizures in rat. Several days prior to experiments, adult males Wistar rats showing prolonged seizure in response to acoustic stimulation (8—10 kHz) were selected. Animals (200—220 g) were housed individually and given access to food and water ad libitum. During the experiment, seizures were induced by microinjection of NMDA. HSP70 (Institute of Cytology RAS) and an inhibitor of HSP70 expression bioflavanoid quercetin (ICN) were used here. The microinjections of HSP70 were made into the 3-d ventricle. After i.c.v. administration of HSP70 or i.p. injections of quercetin, the animals received injections of NMDA and were placed in a box for visual observation of their seizure profile. Seizure and behavior were tested for 50-min in the open field. The following parameters were recorded: the latency and duration of wild running, the number and the duration of the oro-facial, tonic and clonic seizures. The duration of ataxia (the impairment of antigravity reflexes) and stereotypy (rotation), locomotor excitation was assessed. In addition, the number and duration of grooming, vertical and horizontal activities were registered. Here we show that i.c.v. microinjections of NMDA produced the wild running transformed to tonic and clonic components of seizures. Tonic seizures consisted of sustained muscle contraction, whereas clonic seizures consisted of muscle contraction alternating with periods of muscle relaxation. The ataxia, stereotype and locomotor excitation were also observed following the seizures. Quercetin (i.p.) produced a dramatic increase in seizure activity in NMDA-treated rats. The duration of tonic component, oro-facial seizure, stereotype and the latency of locomotor excitation were markedly longer. In contrast, exogenous HSP70 i.c.v. reduced these components of seizures. Moreover, exogenous HSP70 (vs. saline-treated controls) reduced the duration of wild running and the latency of grooming. These results indicate a pro-convulsing effect of selective inhibitor of HSP70 expression. In contrast, exogenous HSP70 considerably reduced NMDA-induced seizure activity. Exogenous HSP70 has been shown to penetrate into the cells and preserve them from the toxic factors as well as endogenous HSP70 [Guzhova, 2005]. HSP capacity to attenuate seizures is due to its interaction with hydrophobic sites of signal peptide of NMDA-glutamate receptors when changing the conformation [Beere et al., 2000]. This may not lead to receptor inhibition, but act on both the ionic channel and the whole NMDA receptor complex. The HSP70 -induced decrease in neurotoxic effect may be associated with Na++ penetration into the cell and an activation of Na+ +-dependent
Psychopharmacol. Biol. Narcol. 2005. Vol. 5, N 2. P. 900
Psyhopharmacology & biological narcology
ISSN 1606-8181
K+ transport, thus reducung intracellular Na++ [Negulyaev et al., 1996]. Quercetin suppresses transcription factor HSF1 and inhibits endogenous HSP70 expression [Nagata et al., 1996], influencing neurotoxic effects of NMDA and the intensity of NMDA-induced seizures. The study was supported by RFRF grant 03-03-33034.
Psychopharmacol. Biol. Narcol. 2005. Vol. 5, N 2. P. 900
Psyhopharmacology & biological narcology
ISSN 1606-8181
