Stereotactic approach and electrophysiological characterization of thalamic reticular and dorsolateral nuclei of the juvenile pig.

Few reports exist on complex functions of pig's central nervous system. A direct access to thalamic structures enables a deeper understanding of neuronal networks. Here we present an easy to implement stereotactic approach to reach both reticular and dorsolateral thalamic nuclei (RTN and LD). In thirteen pigs (7 weeks old) the correct electrode position was confirmed for 22 out of 26 thalamic electrodes (RTN: A+2, L9, V24 and LD: A-2, L5, V20, with bregma A 0, L 0). Quantitative effects of isoflurane/nitrous oxide (State 1) and fentanyl sedation (State 2) were determined by brain hemodynamics and metabolism. Neurophysiologic features were performed by spectral power, coherence and SEP analysis. Brain blood flow (by 21 +/- 13%) and oxidative brain metabolism (CMRO, by 26 +/- 12%, CMRGlucose by 26 +/- 22%) were markedly reduced during State 1 (P<0.05). Regional thalamic blood flow exhibited similar alterations, but side-differences did not occur. State 1 induced quite similar brain activity in cortical as well as thalamic regions investigated. During State 2 electrocortical activity of low frequency ranges was markedly reduced, whereas spectral band power of high frequency ranges was additionally decreased in RTN (P<0.05). Thus, we used a convenient approach for targeted deep electrode implementation and characterized electrophysiological features in RTN and LD.