The comparative distributions of the monoamine transporters in the rodent, monkey, and human amygdala

Abstract

The monoamines in the amygdala modulate multiple aspects of emotional processing in the mammalian brain, and organic or pharmacological dysregulation of these systems can result in affective pathologies. Knowledge of the normal distribution of these neurotransmitters, therefore, is central to our understanding of both the normal processes regulated by the amygdala and the pathological conditions associated with monoaminergic dysregulation. The monoaminergic transporters have proven to be accurate and reliable markers of the distributions of their substrates. The purpose of this review was twofold: First, to briefly recount the functional relevance of dopamine, serotonin, and norepinephrine transmission in the amygdala, and second, to describe and compare the distributions of the monoamine transporters in the rodent, monkey, and human brain. The transporters were found to be heterogeneously distributed in the amygdala. The dopamine transporter (DAT) is consistently found to be extremely sparsely distributed, however the various accounts of its subregional topography are inconsistent, making any cross-species comparisons difficult. The serotonin transporter (SERT) had the greatest overall degree of labeling of the three markers, and was characterized by substantial inter-species variability in its relative distribution. The norepinephrine transporter (NET) was shown to possess an intermediate level of labeling, and like the SERT, its distribution is not consistent across the three species. The results of these comparisons indicate that caution should be exercised when using animal models to investigate the complex processes modulated by the monoamines in the amygdala, as their relative contributions to these functions may differ across species.

Noradrenergic innervation of pyramidal cells in the rat basolateral amygdala

“…The distribution of NET immunoreactivity (NET-ir) closely matched that of tritiated nisoxetine autoradiographic labeling of NET in the amygdala (Hipolide et al, 2005; Smith and Porrino, 2008). Light microscopy demonstrated that NET+ axons in the BLa almost always exhibited co-localization of DBH.…”

Imaging genetics in ADHD: A focus on cognitive control

“…Globus pallidus (Mrzljak et al, 1996) DRD5 (4p16) Whole brain high expression and receptor density Whole brain moderate expression Cerebellum, substantia nigra, hypothalamus, striatum, cerebral cortex, nucleus accumbens, hippocampus and olfactory tubercle (Beischlag et al, 1995;Khan et al, 2000) DBH (9q34) Medulla, pons Whole brain moderate expression Noradrenergic brain stem nuclei, sympathetic ganglion neurons (Hoyle et al, 1994) and hypothalamus, substantia nigra (Westlund et al, 1988) Catecholamines: norepinephrine SLC6A2/NET1 (16q12) Very low expression and receptor density in the brain Whole brain moderate expression Locus coeruleus (Eymin et al, 1995). Amygdala (Smith and Porrino, 2008) ADRA2A (10q25) Very low expression and receptor density in the brain Moderate expression whole brain. Cerebellum (Schambra et al, 2005) Other monoamines MAOA ( (Zill et al, 2007).…”

Where and what is the paralaminar nucleus? A review on a unique and frequently overlooked area of the primate amygdala

“…A study in the squirrel monkey (which occupies a different suborder than the Macaque) shows high TH-positive fiber densities in a region that may encompass the lateral PL, although the PL was not delineated in this study. Immunohistochemical localization of the dopamine transporter (DAT) indicates that there are many DAT+ fibers in the macaque ‘amygdalopiriform’ zone (CTA), which merges with the PL (although the PL was not specifically examined) (Ciliax et al, 1999; Smith and Porrino, 2008). In our material, there are no DAT-positive fibers in the Macaque PL or CTA (personal observations, not shown).…”