3.3. Reduced associative network activation in the CA3 of
129 mouse strain
Altered CA3 associative collateral network activation might underlie the
differences in hippocampal network oscillations across studied mouse
strains (Le Duigou et al. , 2014). For this purpose, we used
antidromic stimulation of CA3 to generate a synaptically-mediated
orthodromic population spike that follows a fast antidromic population
spike (Figure. 3a-b; (Behrens et al. , 2005; Fano et al. ,
2012). Comparison of IO curves for CA3 antidromic population spikes
revealed a statistically significant stimulation strength x strain
interaction (Figure 3c: F(8,180)=2.936, p=0.004) with a mild reduction
of 129 antidromic responses in higher intensity ranges when compared to
B6J substrain (See Figure 3c for posthoc comparisons). Interestingly, we
detected a strong strain effect (Figure 3c: F(2,45)=8.224,
p<0.001) and stimulation strength x strain interaction (Figure
3d: F(8,180)=3.173, p=0.002) for orthodromic populations spikes.
Noteworthy, the orthodromic population spikes of 129 strain were
profoundly reduced (See Figure 3d for posthoc comparisons). To assess
the CA3 associative collateral network activation independent of
antidromic stimulation we calculated normalized orthodromic responses
via dividing orthodromic responses to corresponding antidromic responses
across stimulation strengths and averaged these values within a slice
(one data point per slice; see Figure 3e). Importantly, there was a
strong strain effect (Figure 3e: H(2)=9.201, p=0.01) with a profound
reduction in the normalized orthodromic responses in 129 strain when
compared to B6J (p<0.05). Using the same stimulation
configuration, we recorded orthodromic population spikes in the CA1
(Figure 3f). However, we detected no difference between the strains
(Figure 3c: F(2,34)=0.183, p=0.833). To sum up, these results
demonstrate a differential recruitment of CA3 associative network across
three strains with strong reduction in the 129 when compared B6J.