Volume Changes in Hippocampal Neurons Following Cocaine/Hypoxic Exposure

Abstract

Previous research in our laboratory has revealed that cocaine/hypoxic exposure causes alterations to cerebral mitochondrial O2 consumption in juvenile Fischer rats (Hesker et al., 2004). Other studies suggest that chemicals that alter mitochondrial O2 consumption may cause partial inhibition of neuronal volume regulation (VR) (Patel et al., 1998). These findings led us to examine whether cocaine/hypoxic exposure alters neuronal cell volume in juvenile rats and to examine the effect of the exposure on regulatory volume mechanisms. Juvenile rats were injected with cocaine (30mg/kg dissolved in saline vehicle, IP) and were exposed to 9% O2 (balance N2) for 35 min for 3 consecutive days. Control rats were injected with vehicle and were exposed to normoxic conditions (21% O2, balance N2). Following a 1-day latency period, brains were extracted and a hippocampal cell suspension was created through protease digest, triturition and centrifugation. Cell suspensions were either loaded with calcein-AM for flow cytometry or were cultured under physiological conditions. Flow cytometry revealed that cocaine/hypoxia caused significant cell volume changes. Morphological analyses of neurons performed at day in vitro (DIV) 2 and DIV 5 revealed an increase in soma area was accompanied by a decrease in viable neurons at DIV 2. These differences were resolved at DIV 5. Ion transport indicators indicated that cocaine/hypoxic exposure altered cellular ionic flux. These data are the first to report on the detrimental effects of cocaine/hypoxic exposure (with non-ischemic hypoxia) on neuronal cell volume in juvenile rats. This research was supported by a Peoria Next research grant.