Nociception-Induced Changes in Electroencephalographic Activity and FOS Protein Expression in Piglets Undergoing Castration under Isoflurane Anaesthesia

Abstract

The objective of this study was to investigate the electroencephalographic reaction pattern and FOS protein expression in male piglets undergoing surgical castration under light isoflurane anaesthesia with or without local anaesthesia. The experiment was conducted under isoflurane anaesthesia to exclude the effect of the affective components of pain on the measurements. Changes in the oscillatory activity of the cerebral cortex over a 90 s period after noxious stimulation or simulated interventions were analysed. FOS expression was determined postmortem by performing immunohistochemistry in the dorsal horn of the spinal cord. The analysis of the response to an interdigital pinch revealed a biphasic reaction pattern in the electroencephalogram (EEG) that similarly was observed for the surgical stimuli during the castration procedure in the group without analgesia. This EEG response was attenuated or altered by the application of local anaesthetics. Immunohistochemical staining for FOS indicated a lower expression in the handling and in three local anaesthetic groups than in the animals castrated without pain relief. The findings indicate that EEG and FOS expression may serve as indicators for nociception in piglets under light isoflurane anaesthesia. A lower activation of nociceptive pathways occurs during castration after the application of local anaesthetics. However, EEG and FOS analyses should be combined with additional parameters to assess nociception, e.g., haemodynamic monitoring.

Evaluation of Two Injection Techniques in Combination with the Local Anesthetics Lidocaine and Mepivacaine for Piglets Undergoing Surgical Castration

“…Nyborg et al [46] showed that injection of a local anesthetic before castration reduced the number of Fos-positive neurons in the dorsal horn. Reiser et al found a significant reduction in the Fos staining score in piglets castrated after an injection of lidocaine, mepivacaine and procaine [47]. Only Mepi1 achieved a significant reduction in Fos protein expression compared to the NaCl castrated piglets in the present study.…”

EEG-based sensory testing reveals altered nociceptive processing in elite endurance athletes

“…To account for multiple comparisons, instead of a common approach of an alpha level adjustment, we applied a cluster-based approach, as it has been used in the literature both for 2-dimensional (Akeju et al 2014;Kreuzer et al 2020) and 3-dimensional (Lutz et al 2022;Reiser et al 2022) EEG data. We only reported results as being significant if they occurred in clusters of at least 4 × 4 adjacent significant pixels; this translates to a frequency range of 1.5 Hz and a time range of 15 ms.…”

Electroencephalography-Based Effects of Acute Alcohol Intake on the Pain Matrix

“…To account for multiple comparisons, instead of a common approach of an alpha level adjustment, we have applied a cluster-based approach as it has been used in the literature both for 2-dimensional [45,46] and 3-dimensional [47,48] EEG data. We have only reported results as being significant if they appeared in clusters of at least 3 × 3 pixels in size [36].…”