Over the w t 4 0 years Lhc open field bar ~ o l v e d a a commonly used tool for the rnmumcnt of animal behavior. Thh m i e w taka a dtical look at the we of I& instrument, u&y with regard to the development of a standard form for iu w. The variou procedura and .their sbortcomingr are 'dkmued, w i t h partimlar rcfupacc to the seemingly incooseguential detdk which have b.& showb to ioduhte open-field prformancc per w. Depndent paramrerr are considered both vith regard to their reliability and their validity for the measurement of such undul,ing mnstrucb as emotionality.

The Open-Field Test: a critical review.

Psychiatric disorders are characterized by sex differences in their prevalence, symptomatology and treatment response. Animal models have been widely employed for the investigation of the neurobiology of such disorders and the discovery of new treatments. However, mostly male animals have been used in preclinical pharmacological studies. In this review, we highlight the need for the inclusion of both male and female animals in experimental studies aiming at gender-oriented prevention, diagnosis and treatment of psychiatric disorders. We present behavioural findings on sex differences from animal models of depression, anxiety, post-traumatic stress disorder, substance-related disorders, obsessive–compulsive disorder, schizophrenia, bipolar disorder and autism. Moreover, when available, we include studies conducted across different stages of the oestrous cycle. By inspection of the relevant literature, it is obvious that robust sex differences exist in models of all psychiatric disorders. However, many times results are conflicting, and no clear conclusion regarding the direction of sex differences and the effect of the oestrous cycle is drawn. Moreover, there is a lack of considerable amount of studies using psychiatric drugs in both male and female animals, in order to evaluate the differential response between the two sexes. Notably, while in most cases animal models successfully mimic drug response in both sexes, test parameters and treatment-sensitive behavioural indices are not always the same for male and female rodents. Thus, there is an increasing need to validate animal models for both sexes and use standard procedures across different laboratories.

Linked Articles
This article is part of a themed section on Animal Models in Psychiatry Research. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-20

https://bpspubs.onlinelibrary.wiley.com/doi/pdf/10.1111/bph.12710

Sex differences in animal models of psychiatric disorders.

http://deepblue.lib.umich.edu/bitstream/handle/2027.42/23706/0000678.pdf?sequence=1

Stress, behavioral arousal, and open field activity--A reexamination of emotionality in the rat

Doses of benzodiazepine, clorazepate, and also of the inverse agonist of the benzodiazepine receptor, beta-CCM, which failed to present sedative or postictal depressive effects, were at first determined in a free exploratory situation. Then, the effects of clorazepate dosed at 1.0, 2.0 and 4.0 mg/kg and beta-CCM dosed at 1.0 and 2.5 mg/kg were studied in the light/dark box choice procedure. Clorazepate tended to produce an increase of the time spent by mice in the lit box as well as of the number of transitions between the two boxes, whereas the dose of 1.0 mg/kg of beta-CCM had opposite effects. The benzodiazepine antagonist RO 15-1788 completely counteracted the anxiolytic effects of clorazepate dosed at 2.0 mg/kg and the anxiogenic effects of beta-CCM.

Anxiogenic effects of methyl-β-carboline-3-carboxylate in a light/dark choice situation

Neotic preferences in laboratory rodents: issues, assessment and substrates.

Sprague-Dawley rats, 50, 90, and 150 days old, received 10 tests in an open field. Younger rats were both significantly more active and showed different trends in activity over tests than older rats. Also, as a function of tests, younger rats became less thigmotaxic and showed less defecation, while the oldest rats showed a relatively constant degree of thigmotaxis and a relatively constant level of defecation over tests. Younger rats spent significantly more time grooming than older rats, and all Ss increased grooming time over tests. It was suggested that level of curiosity in young and old rats might be equal but that younger rats are less fearful than older rats.

https://link.springer.com/content/pdf/10.3758%2FBF03336137.pdf

Rats’ performance on repeated tests in the open field as a function of age

Male and female Long-Evans rats were given open-field tests at 30 and/or 120 days of age. At 30 days of age, males and females did not differ in their open-field behavior. At 120 days of age, however, females locomoted more, reared more, and showed less wall-hugging than males, regardless of whether or not the animals had received tests in the open field at 30 days of age. The appearance of sex differences was due to an increase in the scores of the females between 30 and 120 days of age.

/pdf/age-factors-in-sex-differences-in-open-field-activity-of-4mmaykq7jy.pdf

Age factors in sex differences in open-field activity of rats

Female rats locomoted more, were less thigmotactic, and defecated less than males during open-field tests. These sex differences were observed several days before the occurrence of puberty in the females. Thus, sex differences in open-field locomotion follow a different developmental pattern than do sex differences in activity wheel locomotion, which appear only after puberty. This suggests that open-field locomotion and activity wheel locomotion are not expressions of the same underlying neural organization but are, rather, expressions of different neural programs.

/pdf/open-field-sex-differences-prior-to-puberty-in-rats-32gmmocx5a.pdf

Open-field sex differences prior to puberty in rats

Wistar rats were given 16 open-field tests under (a) free exploration (Ss could withdraw from the field into a small dark box), (b) forced exploration, or (c) alternating free and forced exploration. Amount of locomotion and the tendency to leave the peripheral wall were initially suppressed under free exploration but recovered over tests. The tendency to rear in the field remained suppressed under free exploration over all tests. It was suggested that fear functions to inhibit locomotion under forced exploration and functions to motivate and reward escape into the small box under free exploration. As fear habituates, open-field locomotion increases.

/pdf/free-and-forced-exploration-in-rats-as-a-function-of-between-1ta6tvu9hn.pdf

Free and forced exploration in rats as a function of between- vs within-Ss design

One group of rats (Group A-B) was reared on an almond-flavored diet, a second group (Group B-A) on a banana-flavored diet, and a third group (Group C-C), on an unflavored diet. The groups were then given both the banana and almond diets for 2 days. Results showed all three groups preferred almond to banana (almond preference), with Group B-A showing the strongest preference (novelty preference). Results of a second set of tests, following upon an interval during which Groups A-B and B-A had their maintenance flavors switched, were generally consistent with the above but also indicated that a diet’s preferability may depend upon an interaction between its primacy, its familiarity, and its attractiveness.

/pdf/flavor-preferences-in-laboratory-rats-18fakme7ce.pdf

Fred P. Valle

Papers

Rats’ performance on repeated tests in the open field as a function of age

Age factors in sex differences in open-field activity of rats

Open-field sex differences prior to puberty in rats

Free and forced exploration in rats as a function of between- vs within-Ss design

Flavor preferences in laboratory rats