Influence of lactation on motor activity and elevated plus maze behavior

Lactating rats show less noise-induced freezing and fewer inhibitory responses on the 6th day post-delivery when submitted to water and food deprivation in a classical conflict paradigm. Lactating mice go more often to the illuminated chamber in a light-dark cage and stay longer in it than virgin females. The present study was designed to assess the influence of this physiological state, i.e. lactation, on the elevated plus maze (EPM) and open-field behavior in adult female rats. Total (TL) and central (CL) locomotion and rearing (RF) frequencies were measured in an open-field. Number of entries into the open and closed arms as well as the time spent in each of these arms were measured in the EPM. Percent time spent and number of entries into the open arms were calculated and compared. In the open-field, TL was significantly decreased (115 + 10.6 vs 150 + 11.6) while CL and RF did not differ from those presented by virgin rats. In the EPM, lactating rats displayed a significant reduction in percent time spent (10.9 ñ 1.5 vs 17.4 ñ 2.3) in the open arms as well as a tendency to a reduction in percent entries into the open arms (35.7 ñ 4.7 vs 45.7 ñ 4.3). These results show that the physiological state of lactation modulates the open-field and EPM behaviors in rats.

Is perinatal picrotoxin anxiogenic?

Female Wistar rats were exposed to a subconvulsant dose of picrotoxin (0.75 mg/Kg,sc) on day 18 of pregnancy, immediately after paturition and daily during the first 5 days of lactation. In adulthood, the offspring were tested in an open-field, in an elevated plus maze and for social interaction. Results showed increased locomotor activity (75 days of age) and decreased social interaction (90 days of age) in experimental male rats compared to control male rats. No effects on behaviors related to anxiety were observed in males or females tested in the plus maze apparatus. An additional comparison of the activity male animals perinatally treated with picrotoxin showed a lack of the classical sexual dimorphic responses in the open-field (control male = 68.7 ñ 6.31; control female = 98.4 ñ 6.31; edxperimental male = 89.6 ñ 6.32; experimental female = 113.2 ñ 4.74). We suggest that perinatal picrotoxin exposure may interfere with normal male masculinization rather increasing anxiety in male rats