Focal cortical injuries result in death of cortical neurons and their efferents and ultimately in death or damage of thalamocortical relay (TCR) neurons that project to the affected cortical area. Neurons of the inhibitory reticular thalamic nucleus (nRT) receive excitatory inputs from corticothalamic and thalamocortical axons and are thus denervated by such injuries, yet nRT cells generally survive these insults to a greater degree than TCR cells. nRT cells inhibit TCR cells, regulate thalamocortical transmission, and generate cerebral rhythms including those involved in thalamocortical epilepsies. The survival and reorganization of nRT after cortical injury would determine recovery of thalamocortical circuits after injury. However, the physiological properties and connectivity of the survivors remain unknown. To study possible alterations in nRT neurons, we used the rat photothrombosis model of cortical stroke. Using in vitro patch-clamp recordings at various times after the photothrombotic injury, we show that localized strokes in the somatosensory cortex induce long-term reductions in intrinsic excitability and evoked synaptic excitation of nRT cells by the end of the first week after the injury. We find that nRT neurons in injured rats show (1) decreased membrane input resistance, (2) reduced low-threshold calcium burst responses, and (3) weaker evoked excitatory synaptic responses. Such alterations in nRT cellular excitability could lead to loss of nRT-mediated inhibition in relay nuclei, increased output of surviving TCR cells, and enhanced thalamocortical excitation, which may facilitate recovery of thalamic and cortical sensory circuits. In addition, such changes could be maladaptive, leading to injury-induced epilepsy.
The Journal of neuroscience : the official journal of the Society for Neuroscience
April 14, 2010
Agency: NINDS NIH HHS, Id: NS007280
Agency: NINDS NIH HHS, Id: NS06477
Agency: NINDS NIH HHS, Id: P01 NS012151
Agency: NINDS NIH HHS, Id: P01 NS012151-34S1
Agency: NINDS NIH HHS, Id: R01 NS006477
Agency: NINDS NIH HHS, Id: R01 NS006477-43
Agency: NINDS NIH HHS, Id: R01 NS006477-44
Calcium Channels, T-Type
Disease Models, Animal
In Vitro Techniques
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