Each transcript was successfully detected (Figs. and ). Specificity of signal was confirmed using the sense probes, cold displacement, and RNase, which produced negligible signals (not shown). The regional distribution for each mRNA, and for [3H]WAY100,635 binding, was consistent with findings in the hippocampus of other species (see Discussion).
Distribution of five presynaptic protein transcripts in the marmoset hippocampus. A: GAP-43 mRNA. B: synaptophysin mRNA. C: VGluT1 mRNA. D: VGAT mRNA. E: BDNF mRNA. Abbreviations: DG: dentate gyrus. SUB: subiculum.
Distribution of four post-synaptically expressed genes in the marmoset hippocampus. A: MAP-2 mRNA. B: Spinophilin mRNA. C: 5-HT1AR mRNA. D: [3H]WAY100,635 binding.
Effect of Early Deprivation on Expression of Pre-Synaptic Genes
For GAP-43 mRNA () there was an ED-by-subfield interaction (F3,48=2.97, p=0.041), with a trend overall effect of ED (F1,16 =3.40, p=0.084) but no effect of sex or ED-by-sex interaction. GAP-43 mRNA was decreased after ED in the dentate gyrus (F1,18=4.52, p=0.048) and CA3 (F1,18=5.42, p=0.031), but not in CA1 or subiculum.
Figure 3 Expression of pre-synaptic genes in the marmoset hippocampus, in animals subjected to ED (diamonds) and controls (squares). A) GAP-43 mRNA. B) Synaptophysin mRNA. C) VGAT mRNA. D) VGluT1 mRNA. E) BDNF mRNA. DG: dentate gyrus. Sub: subiculum. *p<0.05, (more ...)
Synaptophysin mRNA () was unaffected by ED and showed no interactions with subfield or sex. There was a trend effect of sex (p=0.067), which reflected higher levels of synaptophysin mRNA in females than males in CA3 (p=0.039) and CA1 (p=0.045).
VGAT mRNA () showed an ED-by-subfield interaction (F3,48=2.93, p=0.043) and a trend overall effect of ED (F1,16=4.30, p=0.055), but no effect of sex or ED-by-sex interaction. VGAT mRNA was increased after ED in CA3 (F1,18=9.28, p=0.007) and with a trend in dentate gyrus (F1,18=4.16, p=0.056), but not in CA1 or subiculum.
VGluT1 mRNA () and BDNF mRNA () did not differ after ED or between the sexes, and there were no subfield interactions.
Effect of Early Deprivation on Expression of 5-HT1A Receptors
For 5-HT1AR mRNA () there was an ED-by-sex interaction (F1,16=4.98, p=0.04) and an ED-by-sex-by-subfield interaction (F2,32=3.76, p=0.034). (The subiculum was excluded from the 5-HT1AR mRNA RM-ANOVA due to missing data.) Subsequent analysis showed that, in CA1, 5-HT1AR mRNA was decreased following ED (F1,16=6.41, p=0.022) with no sex interaction. There was an ED-by-sex interaction in the dentate gyrus (F1,16=5.10, p=0.038) and in CA3 (F1,6=6.74, p=0.019). In both subfields, 5-HT1AR mRNA tended to be decreased after ED in females but increased in males, but the post hoc tests in each sex were not significant (p=0.07-0.16). For example, in CA3, control vs ED: females, 66±4 vs. 52±4 nCi/g (t=1.63, p=0.15); males, 54±5 vs. 66±3 (t=2.03, p=0.07).
Figure 4 Expression of post-synaptic genes in the marmoset hippocampus, in animals subjected to ED (diamonds) and controls (squares). A) 5-HT1AR mRNA. In addition to the decrease in CA1 in the ED group, there are ED-by-sex interactions in DG and CA3 (see text). (more ...)
The density of [3H]WAY100,635 binding sites showed an ED-by-subfield interaction (F3,48=3.01, p=0.039) but no interaction with sex. [3H]WAY100,635 binding was decreased by ED in CA1 (F1,16=4.70, p=0.046) with no change in dentate gyrus or subiculum (). In CA3 there was an ED-by-sex interaction (F1,16=5.62, p=0.031); post hoc tests showed increased CA3 [3H]WAY100,635 binding in males after ED (controls vs. ED: 16.2±1.0 vs. 19.4±1.0 nCi/g, t=2.30, p=0.043) with no alteration in females (controls vs. ED: 16.4±2.0 vs. 18.9±0.6 nCi/g, t=1.21, p=0.27).
Effect of Early Deprivation on Expression of Post-Synaptic Genes
MAP-2 mRNA () and spinophilin mRNA () showed no effects of ED, sex, nor an ED-by-subfield interaction.
Effect of Early Deprivation on Hippocampal Volume
For hippocampal volume, there was an effect of sex (F1,19=5.59, p=0.042), with the hippocampus being larger in females (54.3±2.5mm3) than males (46.2±2.3mm3). However, there was no effect of ED, no ED-by-sex interaction, and no left-right difference ().
Hippocampal volumes following early deprivation
Correlations with In Vivo Measures
Several of the exploratory correlations between the in vivo
measures and adolescent gene expression met our criteria for significance. (a) Social play in infancy, which is decreased by ED (Dettling et al, 2002a
), correlated inversely with [3
H]WAY100,635 binding to 5-HT1A
R in CA3 (; r=−0.606, n=20, p=0.005; partialling for ED: r=−0.566, d.f.=17, p=0.011), and with a similar trend in ED and control groups (respectively, r=−0.790, n=11, p=0.004; r=−0.594, n=9, p=0.09). (b) In adolescence, ED marmosets exhibited reduced motivation for palatable reward in terms of fewer operant responses on a progressive ratio reinforcement schedule (Pryce et al, 2004a
), and this measure of mild anhedonia correlated with VGluT1 mRNA in CA1 (; r=0.707, n=15, p=0.003; partialling for ED: r=0.655, d.f.=12, p=0.011); the correlation was present in ED (r=0.719, n=8, p=0.045) and control (r=0.893, n=7, p=0.007) groups. (c) Urinary noradrenaline is raised by ED, from late infancy to adolescence (Pryce et al, 2004b
), and average levels correlated negatively with synaptophysin mRNA (; r=−0.733, n=11, p=0.01), with a similar finding in ED (r=−0.899, n=6, p=0.015) and control (r=−0.700, n=5, p=0.18) groups. (d) Finally, terminal (i.e. adolescent) CSF cortisol level correlated with 5-HT1A
R mRNA, especially in the dentate gyrus (; r=0.530, n=20, p=0.02). The correlation survived partialling for the effect of ED (r=0.503, df16, p=0.033), sex (r=0.519, d.f.16, p=0.027), or both (r=0.496, d.f.15, p=0.043). The correlation was present in the ED group (r=0.818, n=11, p=0.002) but not in the controls (r=0.095, n=8, p=0.82).
Figure 5 Correlations between gene expression and in vivo measures. A: [3H]WAY100,635 binding in CA3 correlates inversely with social play during infancy (; r=−0.606, p=0.005, n=20). B: VGluT1 mRNA in CA1 correlates with the number of progressive (more ...)
Hippocampal volume did not correlate with any of the in vivo measures, and neither impulsivity nor urinary dopamine correlated with expression of any of the genes.