Anhedonia is described as a decreased ability to experience rewarding and enjoyable activities, a core symptom of major depressive disorder. The sucrose preference test (SPT) is a widely used and reliable behavioural test to assess anhedonia in rodents, based on a two-bottle choice paradigm. To date, different protocols are in use, inducing variability between researchers and hampering comparisons between studies. We performed a systematic review of the SPT protocols used in 2021 to identify the parameters in which they differ and their potential impact. We searched a total of four databases (PubMed, Scopus, Web of Science and Science Direct), from 1st January 2021 to 31st December 2021, and screened a total of 1066 articles. After screening by title and abstract, a total of 415 articles were included in this review. We extracted and analysed the different procedures used, the type of sweet solution and the habituation, deprivation, and testing protocols. The overall quality of the studies was considered very good, however, SPT protocols were extremely variable between studies with a total of 65 different habituation protocols and 104 combinations of food/water deprivation and preference testing duration. As the SPT is one of the most used tests to assess anhedonia in rodents, this work raises awareness of the great variability in SPT protocols being currently used. Furthermore, we call for standardization in the protocol used, and overall improvement of data reporting of methodologies and results, to increase the consistency between studies and allow a better comparison of results between different labs.

Chronic pain syndromes encompass several clinical entities that frequently affect the individuals' emotional and cognitive behaviours which, in turn, can also alter pain perception. Additionally, both pain perception and motivational-affective behaviours change with increasing age. In order to evaluate the influence of age upon the interaction between chronic pain and affective/cognitive behaviours, 3-, 10- and 22-month-old rats with 1 month neuropathy (spared nerve injury, SNI model) were compared with age-matched sham-operated controls in the open field (OF; locomotor and exploratory behaviours), elevated plus-maze (EPM; anxiety-like behaviour), forced swimming (FST; depressive-like behaviour), working memory water maze (WM; spatial short-term memory), Morris water maze (MWM; spatial reference memory) and spatial reversal (behavioural flexibility) tests. Locomotor and exploratory activities decreased steadily with age and were further reduced by SNI. Aging was associated with increased anxiety-like behaviour, which was potentiated by SNI in both 3- and 22-month-old rats. The performance in the FST was affected by SNI but only in mid-aged animals. Cognitive performances in the MWM and spatial reversal tests deteriorated with age; however, the SNI lesion was only detrimental in the reversal task to mid-aged animals. Our data demonstrate that the influence of neuropathic pain on affective and cognitive behaviours is age dependent and varies with the behavioural domain that is tested. Importantly, mid-aged animals seem to be more susceptible to depression and cognitive deterioration associated to chronic pain than young and old groups.

The aim of this study was to examine the joint role of demographic, clinical, and psychological variables as predictors of acute postsurgical pain in women undergoing hysterectomy due to benign disorders. A consecutive sample of 203 women was assessed 24 hours before (T1) and 48 hours after (T2) surgery. Baseline pain and predictors were assessed at T1 and postsurgical pain and analgesic consumption at T2. Several factors distinguished women who had no or mild pain after surgery from those who had moderate to severe pain, with the latter being younger, having more presurgical pain, and showing a less favorable psychological profile. Younger age (odds ratio [OR]=0.90, P<.001), presurgical pain (OR=2.50, P <.05), pain due to other causes (OR=4.39, P=.001), and pain catastrophizing (OR=3.37, P=.001) emerged as the main predictors of pain severity at T2 in multivariate logistic regression. This was confirmed in hierarchical linear regression (β=-0.187, P<.05; β=0.146, P<.05; β=0.136, P<.05; β=0.245, P<.01, respectively). Presurgical anxiety also predicted pain intensity at T2. Findings revealed an integrative heuristic model that accounts for the joint influence of demographic, clinical, and psychological factors on postsurgical pain intensity and severity. In further mediation analysis, pain catastrophizing emerged as a full mediator between presurgical anxiety and postsurgical pain intensity. The potential clinical implications for understanding, evaluating, and intervening in postsurgical pain are discussed.