The effects of the time of the day and the pinealectomy on anxiety-like behaviour in male Wistar rats

Abstract

The previous studies on the anxiety-like behaviour in rats by using elevated plus maze and open field have provided rather unequivocal results because they obtained data at different times of the day. These studies have never investigated the effects of the different times of day in a single research paradigm even though the results of such studies are generally attributed to the different measurement times. Thus, we aimed to examine the effects of the time of the day and the pinealectomy on anxiety-like behaviour in male Wistar albino rats by using elevated plus maze and open field in this study. Experiments were performed with control and pinealectomy groups at the four different time points (6:00, 12:00, 18:00 and 24:00 hr; LD 12:12, lights on at 6:00 h and off at 18:00 h). In open field, the main effect of the measurement time was significant on the total distance travelled, the mobility and the velocity. In elevated plus maze, the main effect of the measurement time was significant on the total distance travelled, the total entry to closed arms and mobility. The main effect of the pinealectomy was insignificant on all of the measured parameters in both open field and elevated plus maze except for the total entry to closed arms in elevated plus maze. The results of the present study showed for the first time that the time of the day when the measurements are performed is important on the anxiety-like behaviour of the Wistar albino rats.

Pinealectomy and Exogenous Melatonin Regulate Anxiety-Like and Depressive-Like Behaviors in Male and Female Wistar Rats

“…This assumption is in agreement with the findings of the previous studies suggesting that pinealectomy was partially involved in anxiety behavior [43,44] and seems to be coherent with another report demonstrating an important role of both maternal and postnatal pinealectomy in organization of affective behaviors in another species, in this case the Siberian hamster [43,44]. Conversely, some studies reported insignificant effect of pinealectomy which is inconsistent with our study [44]. It is likely that this disagreement would be due to the experimental conditions which are different, especially the time of the day when the measurements are performed [44] or doses and mode of Mel administration adopted [43,44].…”

“…Conversely, some studies reported insignificant effect of pinealectomy which is inconsistent with our study [44]. It is likely that this disagreement would be due to the experimental conditions which are different, especially the time of the day when the measurements are performed [44] or doses and mode of Mel administration adopted [43,44]. However, a complementary experimental research is needed for illuminating the role of pineal gland in anxiety behavior.…”

“…Since the rhythm of the endogenous Mel release in the Px animals is abolished, and since this endogenous rhythm in the sham Px animals is intact; we hypothesized that the increase in anxiety level observed in Px rats would be due to the absence of Mel synthesis and release. This assumption is in agreement with the findings of the previous studies suggesting that pinealectomy was partially involved in anxiety behavior [43,44] and seems to be coherent with another report demonstrating an important role of both maternal and postnatal pinealectomy in organization of affective behaviors in another species, in this case the Siberian hamster [43,44]. Conversely, some studies reported insignificant effect of pinealectomy which is inconsistent with our study [44].…”

Impact of Melatonin Deficit on Emotional Status and Oxidative Stress-Induced Changes in Sphingomyelin and Cholesterol Level in Young Adult, Mature, and Aged Rats

“…Our findings suggesting a lack of anxiety in the young adult rats with pinealectomy compared to the sham rats contradict other reports [ 28 , 29 , 30 , 31 ]. However, some crucial factors might explain the divergence in the reported effects of pinealectomy on anxiety behavior, such as age and time of testing after the removal of the pineal gland [ 31 , 32 ] and/or the hour of the day of examination [ 32 ], which determine the direction of the effects on anxiety. The depressive-like behavior associated with pinealectomy in adult rats agrees with our and other reports [ 26 , 29 , 33 ].…”

Lycium barbarum L. (goji berry) fruits improve anxiety, depression-like behaviors, and learning performance: the moderating role of sex

“…The closed arms were enclosed by 41-cm-tall black Plexiglas. All animals were tested by means of the procedure described by Karakas et al (2011) and Kaya et al (2011). Videotapes with Observer Software (Ethovision XT, Noldus Ethovision, Version 6) were recorded and analyzed for all anxiety-like behaviors (including distance, duration in the open arms, frequency in the closed arms, mobility, and velocity).…”