Chapter 3: Statistical Analyses and Results

3: EPM Results

Each animal was tested once at each of the three testing periods in the EPM, as research suggests the EPM can produce habitation effects if tested within two weeks after first trial (Bessa et al., 2005). See Table 2 above for F ratios and Table 3 for significant sex differences, across the three testing periods.

BZP and MAtreated: Percentage of Entries of the open arms of the EPM at 30 day wash- out period.

Figure 8: Mean (±S. E. M.) percent of open arm entries for control (Saline), BZP (Dose 1 - 5mg/kg; Dose 2 - 10mg/kg; Dose 3 - 20mg/kg) and MA (Dose 1 - 0.5mg/kg; Dose 2 - 1.0mg/kg; Dose 3 - 2.0mg/kg) for PND31-40, 41-50 and 51-60 male and female rats. . † differs significantly (p<.05) from chance expectancy of 50% (one-sample t test); . * significantly different (p<.05) from saline for that particular drug; a,b difference between groups with superscript in common significant (p<.05) for that particular drug.

Figure 8 illustrates that administration of BZP during PND31-40 significantly affected

from saline and the two lower doses. Likewise, the highest BZP dose administered during PND41-50 was significantly different from saline controls, but not from the other two BZP doses. However, it was the lowest BZP dose administered during PND51-60 that was

significantly different from control animals. There are also differences between the doses of BZP administered during PND51-60, with the lowest dose (5 mg/kg) significantly different from the middle dose (10 mg/kg) and the middle BZP dosed animals significantly different from the highest BZP (20 mg/kg) treated rats in the percentage of entries of the open arms of the EPM. With the exception of MA- treated females during PND31-40 and BZP and MA- treated during PND41-50 all other female treated rats made significantly more entries of the open arms of the EPM than similar treated male rats.

A significant dose x sex interaction for PND51-60- MA-treated rats (F (1, 72) 2.92, P<.0397)

outlined in Figure 9 revealed that the two lower doses of the drug increased this response for female but not male rats. However, males treated with 1.0 mg/kg made fewer entries of the open arms than those treated with 0.5 mg/kg. Female rats treated with 2 mg/kg scored lower on this response than those treated with 1 mg/kg.

Drug x sex interaction for PND51-60 MA treated rats: Percentage of Entries of the open arms of the EPM at 30 day wash-out period.

Figure 9: Mean (±S. E. M.) percentage of open arm entries for control (Saline), MA PND 51-60 treated male and female rats. * significantly different (p<.05) from saline for that particular sex. a,b difference between groups with superscript in common significant (p<.05) for that particular drug.

BZP and MAtreated: Percentage of time in the open arms of the EPM at 30 day wash- out period.

Figure 10: Mean (±S. E. M.) percentage of time spent in the open arms of the EPM for control (Saline), BZP (Dose 1 - 5mg/kg; Dose 2 - 10mg/kg; Dose 3 - 20mg/kg) and MA (Dose 1 - 0.5mg/kg; Dose 2 - 1.0mg/kg; Dose 3 - 2.0mg/kg) for PND 31-40, 41-50 and 51-60 male and female rats. † differs significantly (p<.05) from chance expectancy of 50% (one-sample t test); . * significantly different (p<.05) from saline for that particular drug; a,b difference between groups with superscript in common significant (p<.05) for that particular drug.

Figure 10 illustrates that PND31-40 BZP treated rats spent significantly less percentage of time in the open arms of the EPM compared to saline controls and the 5 mg/kg and 10 mg/kg treated

rats. Rats from both the lowest and the highest PND41-50 BZP treatment groupswere

significantly different from controls, and 10 mg/kg BZP treated rats. For PND51-60 the BZP 10 mg/kg treated rats spent significantly more time in the open arms of the EPM compared to the higher (20 mg/kg) and lower (5 mg/kg) treated rats, but results were not statistically

different from control rats. Although thelowest MA dosed rats(0.5 mg/kg) spent significantly

more time in the open arms than control animals, and the two MA-treatedgroups, a significant

dose x sex interaction (F (3,72) 4.51, P<.0059) outlined in Figure 11 revealed that this response was increased by the two lower doses for females only. Although no male group differed significantly from saline, both higher doses significantly reduced time in the open arms compared with the lowest dose.

Similar to the results for total closed arm entries, there was a significant difference between the

sexes for both BZP- and MA-treatedPND41-50 and 51-60 rats, with female treated rats

spending a significant longer percentage of time in the open arm, than male treated rats.

Drug x sex interaction for PND51-60 MA treated rats: Percentage of time spent in the open arms of the EPM at 30 day wash-out period.

Figure 11: Mean (±S. E. M.) percentage of time spent in the open arms for control (Saline), MA PND 51-60 treated male and female rats. * significantly different (p<.05) from saline for that particular sex. a,b difference between groups with superscript in common significant (p<.05) for that particular drug.

BZP and MAtreated: Entries of the closed arms of the EPM at 30 day wash-out period.

Figure 12: Mean (±S. E. M.) entries of the closed arms of the EPM for control (Saline), BZP (Dose 1 - 5mg/kg; Dose 2 - 10mg/kg; Dose 3 - 20mg/kg) and MA (Dose 1 - 0.5mg/kg; Dose 2 - 1.0mg/kg; Dose 3 - 2.0mg/kg) for PND31-40, 41-50 and 51-60 male and female rats.

Figure 12 illustrates that there were no significant dose effects for all treatment groups on entries of the closed arms in the EPM at the 30 day wash-out period. However, again there

were sex effects for both BZP- and MA-treated rats at bothPND41-50 and 51-60, with female

treated rats making more closed arm entries than male treated rats.

Summary of EPM results for 30 day wash-out period.

The EPM is currently one of the most popular in vivo animal tests (Carobrez & Bertoglio, 2005) and research suggests that rats prefer the closed arms of the maze to the open arms and this preference is caused by fear or anxiety (Pellow et al., 1985; Flint, 2003). The pattern of results suggests that the highest dose of BZP administered during the PND31-40 and 41-50

affected the rats’ tendencyto enter and spend time in the open arms of the EPM. Inconsistent

with a dose-related increase in avoidance of the open arms, the lowest BZP dose group

administered during PND51-60 made significantly fewer entries of the open arms of the EPM. Consistent with the results found in the Y-Maze and light/dark emergence box, female rats were more active than male rats. However, this effect was only significant for animals treated during PND41-50 and 51-60.

While there appears to be a general pattern of increased avoidance with escalating BZP dose, in the EPM for rats administered BZP during PND31-40 and 41-50, the results for BZP and MA administered during PND51-60 are not as clear. The lowest MA dose administered at PND51-

60 resulted in a significantly longer percentage of time spent in the open arms, indicative of decreased anxiety compared to saline treated rats. PND51-60 female rats administered either 0.5 mg/kg or 1.0 mg/kg MA made significantly more entries and spent a longer percentage of time in open arms compared to saline treated female rats. Interestingly, the female rats administered the highest MA dose (2.0 mg/kg) were comparable to the saline treated female rats in percentage of entries, with the saline treated rats and MA 2.0 mg/kg female rats choosing to enter the open arms of the EPM 43 percent of the time. Likewise, the saline treated female rats and MA 2.0 mg/kg spent a similar amount of time, 38 percent and 41 percent retrospectively in the open arms. It appears that female rats administered MA during

PND51-60 may be less than or equally anxious to untreatedanimals.

In document The behavioural implications of postnatal exposure to benzylpiperazhie and methamphetamine a longitudinal doserelated study in male and female rats (Page 80-85)