Calcium movements in traumatic brain injury: the role of glutamate receptor-operated ion channels.
Ion-selective microelectrodes were used to study acute effects of N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy- 5-methyl-4-isoxazole (AMPA) receptor blockade on posttraumatic calcium disturbances. An autoradiographic technique with 45 Ca2+ was used to study calcium disturbances at 8, 24, and 72 h. Compression contusion trauma of the cerebral cortex was produced by a 21-g weight dropped from a height of 35 cm onto a piston that compressed the brain 2 mm. Pre- and posttrauma interstitial [Ca2+] ([Ca2+]e) concentrations were measured in the perimeter, i.e., the shear stress zone (SSZ) and in the central region (CR) of the trauma site. For the [Ca2+]e studies the animals were divided into controls and groups pretreated with dizocilipine maleate (MK-801) or with 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo[F]quinoxaline (NBQX). In all groups, [Ca2+]e decreased from pretrauma values of approximately 1 mM to posttraumatic values of 0.1 mM in both the CR and the SSZ. This was followed by a slow restitution toward pretraumatic levels during the 2-h observation period. There was no significant difference in recovery pattern between controls and pretreated animals. Accumulation of 45Ca2+ and serum proteins was seen in the entire SSZ, while neuronal necrosis was confined to a narrow band within the SSZ. The CR was unaffected apart from occasional eosinophilic neurons and showed no accumulation of 45Ca2+. Posttraumatic treatment with MK-801 or NBQX had no obvious effect on neuronal injury in the SSZ. We conclude that (a) acute [Ca2+]e disturbances in compression contusion brain trauma are not affected by blockade of NMDA or AMPA receptors, (b) 45Ca2+ accumulation in the SSZ reflects mainly protein accumulation due to blood-brain barrier breakdown rather than cell death, and (c) acute cellular Ca2+ over-load per se does not seem to be a major determinant of cell death after cerebral trauma in our model.
Nilsson
P
P
Department of Neurosurgery, Uppsala University Hospital, Sweden.
Laursen
H
H
Hillered
L
L
Hansen
A J
AJ
D000818:Animals; D001345:Autoradiography; D001930:Brain Injuries / Q000378:metabolism* / Q000473:pathology; D002118:Calcium / Q000378:metabolism*; D016291:Dizocilpine Maleate / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D007473:Ion Channels / Q000502:physiology*; D008297:Male; D009336:Necrosis; D009474:Neurons / Q000473:pathology; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors / Q000502:physiology; D017470:Receptors, Glutamate / Q000502:physiology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000502:physiology
D018691:Excitatory Amino Acid Antagonists; D007473:Ion Channels; D011810:Quinoxalines; D018091:Receptors, AMPA; D017470:Receptors, Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; D016291:Dizocilpine Maleate; D002118:Calcium