Sexual dimorphism of medium-sized neurons with spines in human nucleus accumbens

Abstract

The nucleus accumbens is a limbic nucleus, representing part of the striatum body, and together with the caudate nucleus and putamen, it lies on the septum. The aim of this study was to examine morphological sexual dimorphism in spine density and also to undertake an immunohistochemical study of expression for estrogen and progesterone receptors in the medium-sized neurons in the nucleus accumbens. The research was conducted on twenty human brains of persons of both sexes, between the age of 20-75 years. The Golgi method was applied to determine the types and subtypes of neurons, morphologies of soma, dendrites and axons, as well as the relations between the cells and glial elements. The following were quantitatively examined: the maximum diameter of the neurons, the minimal diameter of the neurons, and the total length of the dendrites. The expression of receptors for estrogen and progesterone, their distribution and intensity were defined immunohistochemically. The parameters of the bodies of neurons in the shell and core of the nucleus accumbens were studied in both men and women. No statistically significant differences were found. Examination of the spine density showed statistical significance in terms of a higher density of spines in women. Immunohistochemically, in the female brain estrogen expression is diffusely spread in a large number of neurons; it is extra nuclear, of granular appearance and high intensity. In the male brain, expression of estrogen is visible and distributed over about one half of different types of neurons; it is extra nuclear, of granular appearance, mostly of middle and low staining intensity. Expression of progesterone in the female brain was very discreet and on a very small number of neurons; it was extra nuclear and with a weak staining intensity. Expression of progesterone in the male brain was distributed on a small number of neurons. It had a granular appearance, it was extra nuclear, with a very low staining intensity. Our results show differences in the morphology as well as expression of receptors for estrogen and progesterone on medium-sized neurons with spines in the nucleus accumbens of men and women

Sex Differences in Medium Spiny Neuron Excitability and Glutamatergic Synaptic Input: Heterogeneity Across Striatal Regions and Evidence for Estradiol-Dependent Sexual Differentiation

“…One neuroanatomical correlate of increased excitatory synapse number onto female compared with male rat AcbC MSNs was concomitant increased dendritic spine density ( 87 , 88 ). This sex difference in dendritic spine density was also identified in adult human AcbC, with increased dendritic spine density on female compared with male MSNs ( 95 ). In other brain regions, dendritic spine density has long been documented to be sensitive to estradiol exposure, either via endogenous exposure via the estrous or menstrual cycles, or exogenous ( 96 – 98 ).…”

Recent Perspectives on Sex Differences in Compulsion-Like and Binge Alcohol Drinking

“…Likewise, manipulations of NAcb shell also reduce alcohol consumption [ 130 , 131 , 132 ] (see below). The NAcb is a sexually dimorphic region [ 133 , 134 ] where females display greater dendritic spine density, larger dendritic spine heads, and greater variability in spine density than males [ 135 , 136 ]. Further, there are also known sex differences in NAcb physiology, including facilitated dopamine release and neuronal excitability by estradiol [ 137 , 138 , 139 , 140 ], that are likely to contribute to enhanced reward-seeking behavior in females vs. males.…”

Interactions between estrogen receptors and metabotropic glutamate receptors and their impact on drug addiction in females

“…The nucleus accumbens core (NAcC) is known for its unique sex differences even outside the context of drug-induced plasticity. NAcC MSNs receive increased numbers of excitatory glutamatergic synapses in females relative to males (Sazdanović et al, 2013). Perinatal estradiol exposure in males causes the relative decrease (Cao et al, 2016).…”