Effect of focal cerebral ischaemia on modulatory neurotransmitter receptors in the rat brain: An autoradiographic study

Neurotransmission is strongly affected after ischaemic insult. It is postulated that modulatory neurotransmitter systems and their receptors play a role in experience-dependent and restoration plasticity. In this study, muscarinic cholinergic, serotonergic 5-HT2A/2C, dopaminergic D1 and noradrenergic β1 receptors were examined after focal cerebral ischaemia in different brain regions, using quantitative in vitro autoradiography. There were six evaluated time points: 4 h, 1, 4, 7, 28 and 60 days after the insult. Rats received unilateral ischaemic lesions through photothrombosis in the primary somatosensory cortex. In the lesion core, 5-HT2A/2C, D1 and β1 receptor binding values return to control levels 28 days after displaying initial decreases, while muscarinic binding remains very low, at 30% of controls. From 4 h to 60 days post-stroke no changes are observed in the perilesional tissue. In contrast, in remote brain regions, a bilateral increase of serotonergic 5-HT2A/2C receptor binding in the somatosensory cortex at the striatum level is observed after 4 h and after 7 days post-stroke. In addition, a bilateral decrease of muscarinic cholinergic receptor binding in the hippocampus is observed at each time point examined. This study points to a complex and remote reaction of modulatory systems in response to ischaemic lesions.