Background & Aims
While the role of the anterior cingulate cortex (ACC) in emotion and pain processing have been established(Fuchs et al., 2014; Vogt, 2005), there is a gap in our understanding regarding its involvement in processing positive affective touch. Previous studies have described areas 24a and 24b in the mouse brain ACC as key areas for emotional processing and pain, specifically the affective/motivational aspect of pain (Fuchs et al., 2014; Kimmey et al., 2022; Vogt, 2005), and that they are strongly connected to the basolateral amygdala (BLA)(Fillinger et al., 2017, 2018).
The aim of this study was to further understand the involvement of the ACC and its pathways in processing affective touch. To achieve this, cell activity in the ACC and BLA was measured following soft touch with a blanket and dynamic touch with a brush.
Methods
We used FosTRAP crossed to a tdTomato line to examine activity dependent cell-labeling in the ACC and BLA after soft touch stimuli by using a blanket cage (n=4) and dynamic brush (n=4) after 3 or 7 days of acclimatization, respectively. Mice in the blanket cage, were given 4-hydroxytamoxifen 30 minutes before the experiment to allow tdTomato expression, and perfusion and microscopy was done 1 week later. A place preference test was performed using a blanket cage and a regular cage, between which the mice could move freely.
Dynamic touch (n=4) was examined with a soft brush, varying the location and with intermittent pauses, to prevent receptor fatigue (stroke velocity 18-22 m/s). For this experiment, activity was examined using immunohistochemistry with antibodies for c-Fos.
Mice kept in their homecage were used as controls (n=4). Additionally, CalcaCre(+/-) knock-in/knock-out mice, placed in the blanket cage, served as controls specifically for the BLA (n=3).
Results
In the place preference test for the blanket, mice spent significantly more time in the blanket cage (n=12, p<0.01, t-test), however, no significant difference was found when comparing average activity to controls (p>0,05).
Preliminary results indicate that the most notable increase in cell activity in the ACC was seen after dynamic touch stimulus and that the BLA had more activity after dynamic touch stimulation compared to after blanket cage stimulation. A similar trend was observed in the ACC, however, a direct comparison has not yet been made as immunostaining was used for dynamic brush stimulus but not blanket cage. After dynamic touch stimulus, more activity was seen in 24a than 24b, the same was not seen in controls or after soft touch experiments.
The level of Fos activity in the ACC corresponded to the activity level in the BLA.
Conclusions
The outcomes of the place preference test indicate that the blanket cage is more appetitive to mice compared to a regular cage. However, whether this tactile experience qualifies as pleasant touch remains uncertain. As an affective touch assay, dynamic touch seems to be more effective compared to blanket cage in terms of activated neurons.
The observed concurrent increase in activity in the ACC and amygdala following both soft and dynamic touch suggests the potential involvement of established signalling pathways between these regions in the processing of affective touch.
Moving forward, the dynamic touch assay will be adapted to assess pleasant touch and in further experiments, compared to responses to painful stimuli. Utilising the same mouse strain, calcium imaging can further help visualise the activity patterns associated with affective painful and pleasant touch in the ACC and BLA.
References
Fillinger, C., Yalcin, I., Barrot, M., & Veinante, P. (2017). Afferents to anterior cingulate areas 24a and 24b and midcingulate areas 24a’ and 24b’ in the mouse. Brain Struct Funct, 222(3), 1509-1532. https://doi.org/10.1007/s00429-016-1290-1
Fillinger, C., Yalcin, I., Barrot, M., & Veinante, P. (2018). Efferents of anterior cingulate areas 24a and 24b and midcingulate areas 24a’ and 24b’ in the mouse. Brain Struct Funct, 223(4), 1747-1778. https://doi.org/10.1007/s00429-017-1585-x
Fuchs, P. N., Peng, Y. B., Boyette-Davis, J. A., & Uhelski, M. L. (2014). The anterior cingulate cortex and pain processing. Front Integr Neurosci, 8, 35. https://doi.org/10.3389/fnint.2014.00035
Kimmey, B. A., McCall, N. M., Wooldridge, L. M., Satterthwaite, T. D., & Corder, G. (2022). Engaging endogenous opioid circuits in pain affective processes. J Neurosci Res, 100(1), 66-98. https://doi.org/10.1002/jnr.24762
Vogt, B. A. (2005). Pain and emotion interactions in subregions of the cingulate gyrus. Nat Rev Neurosci, 6(7), 533-544. https://doi.org/10.1038/nrn1704
Presenting Author
Sara Simfors
Poster Authors
Sara Simfors
PhD student; MD
Göteborg university
Lead Author
Anita Tran
University of Gothenburg
Lead Author
Alexander Stjernvall
University of Gothenburg
Lead Author
Konstantina Ioneskou
University of Gothenburg
Lead Author
Martin Hezsö
University of Gothenburg
Lead Author
Line Loken
University of Gothenburg
Lead Author
Topics
- Mechanisms: Biological-Systems (Physiology/Anatomy)