Alterations of cholinergic receptors and the vesicular acetylcholine transporter after lateral fluid percussion injury in newborn piglets

Abstract

Traumatic brain injury (TBI) is one of the leading causes of death and disability in children. Adult animal models of TBI showed cholinergic alterations. However, there is no comparable data on immature animals. Therefore, this study investigates cholinergic markers in a large animal model of juvenile TBI. Twenty-seven female newborn piglets were subjected to lateral fluid percussion (FP) injury and compared with 12 untreated animals. After 6 h, animals were sacrificed and the brains removed. The hemispheres ipsilateral to FP-TBI from seven piglets and corresponding hemispheres from six control animals were used for autoradiography. Receptor density was determined with [(3)H]epibatidine (nicotinic acetylcholine receptors) or [(3)H]QNB (muscarinic acetylcholine receptors). The density of the vesicular acetylcholine transporter (vAChT) was assessed with (-)-[(3)H]vesamicol. Cerebral blood flow was measured by coloured microsphere method. Cerebral blood flow and brain oxygen delivery were transiently reduced early after FP-TBI (P < 0.05). TBI caused reductions of muscarinic acetylcholine receptor density (fmol/mg) in the basal forebrain (sham: 10797 +/- 1339, TBI: 8791 +/- 1031), while nicotinic acetylcholine receptor remained stable. Significant increases in vAChT density (fmol/mg) were observed in the basal forebrain (sham: 2347 +/- 171, TBI: 2884 +/- 544), putamen (sham: 2276 +/- 181, TBI: 2961 +/- 386), cortex (sham: 1928 +/- 262, TBI: 2377 +/- 294), thalamic areas (sham: 2133 +/- 272, TBI: 2659 +/- 413), hippocampus (sham: 2712 +/- 145, TBI: 3391 +/- 501) and hypothalamus (sham: 2659 +/- 139, TBI: 3084 +/- 304). Cholinergic markers are altered after mild-to-moderate TBI in the immature brain. Whereas the ACh receptors are stable in almost any brain region after TBI, vAChT expression increases after trauma at the employed severity of this specific trauma model.