Prolonged latency of pupillary light reflex in confined sows: Possible stress-related symptom?

Effects of confinement on physiological and psychological responses and expression of interleukin 6 and brain derived neurotrophic factor mRNA in primiparous and multiparous weaning sows

“…This study found that long-term space constraints led to a significant prolonged latency of the PLR in sows, and the latency of the PLR in high parity sows that had undergone multiple space constraints during gestation was significantly higher than that of young sows ( Figure 2B ). This was consistent with the phenomenon of prolonged latency of the PLR in sows that had been studied in our earlier experiments [ 5 ].…”

“…Five sows were obtained from different experiment groups on the third day after weaning, the PLR index of every group sow was measured by a new portable pupil detector (NeurOptics PLR-200 Pupillometer, NeurOptics Inc., Irvine, CA, USA). Bao et al [ 5 ] found that eye illumination was suitable for the detection of the sows’ pupils under the condition of <250 lx, the pulse intensity was 180 uw, and the pulse duration was 802 ms. The operator kept the tested sow’s head from unintentionally shaking so that the lens of the pupil detector remained at the same level as the eye; if the sow’s eyes were not open, the operator could skillfully open their eyelid for detection.…”

“…Pupillary light reflex (PLR), the contraction response of the pupil to light stimulation [ 5 ], is mainly controlled by the sympathetic and parasympathetic nerves of the autonomic nervous system; hence, pupil changes are not influenced by the external environment or psychological stress [ 6 ]. Clinical observation found that PLR parameters were different between patients with mental depression and healthy people [ 7 ].…”

“…Conventional pupillary reflex studies were focused on the clinical studies of human disease [ 10 ], but few reported on animals. In our previous study, we first used the PLR method to evaluate sows’ psychological status and found that confined sows had longer pupillary light reflex time (PLRT) than those of grouped sows [ 5 ]. Although the preliminary work had not yet confirmed that PLRT delay was the result of sows’ psychological depression, a large number of human studies had shown that the latency time of the pupil constriction onset of depressive patients was significantly longer than that of normal subjects [ 11 ].…”

A pilot study on differential expression of microRNAs in the ventromedial prefrontal cortex and serum of sows in activity restricted crates or activity free pens

“…In this study, the detection of miR-134 in the vMPFC of RC sows was higher than that of the FP sows (p<0.01). Overexpression of miR-134 inhibited the translation of LIMK1 mRNA, shortened the dendritic spine, and reduced the sensitivity of the animal to stress [17], which may be related to the PLR in the activity restricted environment [18]. Such pathways can modulate chronic stress-induced structural plasticity and depression-like behaviors [19].…”