Abstract
Sex differences exist in how the brain regulates motivated behavior and reward, both in normal and pathological contexts. Investigations into the underlying neural mechanisms have targeted the striatal brain regions, including the dorsal striatum and nucleus accumbens core and shell. These investigations yield accumulating evidence of sexually different electrophysiological properties, excitatory synaptic input, and sensitivity to neuromodulator/hormone action in select striatal regions both before and after puberty. It is unknown whether the electrical properties of neurons in the nucleus accumbens shell differ by sex, and whether sex differences in excitatory synaptic input are present before puberty. To test the hypothesis that these properties differ by sex, we performed whole-cell patch-clamp recordings on male and female medium spiny neurons (MSNs) in acute brain slices obtained from prepubertal rat nucleus accumbens shell. We analyzed passive and active electrophysiological properties, and miniature EPSCs (mEPSCs). No sex differences were detected; this includes those properties, such as intrinsic excitability, action potential afterhyperpolarization, threshold, and mEPSC frequency, that have been found to differ by sex in other striatal regions and/or developmental periods. These findings indicate that, unlike other striatal brain regions, the electrophysiological properties of nucleus accumbens shell MSNs do not differ by sex. Overall, it appears that sex differences in striatal function, including motivated behavior and reward, are likely mediated by other factors and striatal regions.
Highlights
Numerous neural sex differences have been identified (McCarthy et al, 2012; Cahill, 2014)
Regarding action potential properties found to differ by sex in the same developmental period in the dorsal striatum (Dorris et al, 2015), these properties do not differ by sex in the nucleus accumbens shell, including action potential threshold (Fig. 2B; U(61) ϭ 400.0; p Ͼ 0.05), and action potential afterhyperpolarization peak (Fig. 2C; t(61) ϭ 1.68; p Ͼ 0.05)
All medium spiny neurons (MSNs) action potential properties assessed were comparable across sex, including those found to differ in other striatal regions during the same developmental period
Summary
Numerous neural sex differences have been identified (McCarthy et al, 2012; Cahill, 2014). Research has primarily focused on brain regions involved in reproduction in adult, postpubertal animals (Breedlove and Hampson, 2002; De Vries, 2004), which display sex differences in neuroanatomy and physiology. Received December 1, 2015; accepted January 25, 2016; First published February 05, 2016. Received December 1, 2015; accepted January 25, 2016; First published February 05, 2016. 1The authors declare no competing financial interests. 2Author Contributions: J.A.W. and J.M. designed research; J.A.W., D.M.D., and J.C. performed research; J.A.W., T.W., C.A.H., D.M.D., and J.M. analyzed data; J.A.W. and J.M. wrote the paper
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