GABA and glutamate in mating‐activated cells in the preoptic area and medial amygdala of male gerbils

Abstract

The posterodorsal medial amygdala (MeApd), the posterodorsal preoptic nucleus (PdPN), and the medial cell group of the sexually dimorphic preoptic area (mSDA) contain cells that are activated specifically at ejaculation as assessed by Fos expression. The mSDA also expresses Fos early in the mating context. Because little is known about the neurotransmitters of these activated cells, the possibility that they use gamma-aminobutyric acid (GABA) or glutamate was assessed. Putative glutamatergic cells were visualized with immunocytochemistry (ICC) for glutamate and its neuron-specific transporter. Their distributions were compared with those of GABAergic cells visualized with ICC for the 67-kDa form of glutamic acid decarboxylase (GAD(67)) and in situ hybridization for GAD(67) messenger RNA (mRNA). Colocalization of Fos and GAD(67) mRNA in recently mated males indicated that half of the activated cells in the PdPN, mSDA, and lateral MeApd are GABAergic. Colocalization of Fos and glutamate suggested that a quarter of the activated mSDA and lateral MeApd cells are glutamatergic. The PdPN does not appear to have glutamatergic cells. In the lateral MeApd, the percentage of activated cells that are GABAergic (45%) matches the percentage that project to the principal part of the bed nucleus of the stria terminalis (BST; 43%), and the percentage likely to be glutamatergic (27%) matches the percentage projecting to the mSDA (27%). The latter could help to trigger ejaculation. The distribution of GABAergic and putative glutamatergic cells in the caudal preoptic area, caudal BST, and medial amygdala of male gerbils is also described.

Sexually Dimorphic Synaptic Organization of the Medial Amygdala

“…Although 50 -90% of the total population of rat MeA neurons is GABAergic (Mugnaini and Oertel, 1985), glutamatergic neurons have been reported in the gerbil MeApd (Simmons and Yahr, 2003). Because no sex difference was detected in the number of MeApd neurons in the current sample, an effect on intrinsic afferents would likely be accompanied by additional differences; for example, in males, each presynaptic glutamatergic MeApd neuron might form more intrinsic synapses and/or the proportion of glutamatergic MeApd neurons might be greater.…”

Effects of season, testosterone and female exposure on c-fos expression in the preoptic area and amygdala of male green anoles

“…This idea is compatible with work in some other species. For example, in male gerbils, c-fos and the inhibitory neurotransmitter GABA are co-localized in half of POA and AMY neurons, whereas only about one-fourth of the neurons co-express c-fos and the excitatory neurotransmitter glutamate, following mating (Simmons and Yahr, 2003). In addition, hormonal manipulations can modulate GABA receptor function (Clark and Henderson, 2003).…”

Glutamate Microinjected in the Posterodorsal Medial Amygdala Induces Subtle Increase in the Consumption of a Three‐Choice Macronutrient Self‐Selection Diet in Male Rats

“…The orexigenic effect of neuropeptide Y needs the concomitant activation of N-Methyl-D-aspartate glutamate receptors in this same area (Lee and Stanley, 2005). Notably, glutamate immunoreactivity and receptors can be found in the MePD (Polston et al, 2001;Simmons and Yahr, 2003;Bian et al, 2008;de Castilhos et al, 2008). Afferent excitatory pathways to this subnucleus use glutamate as neurotransmitter to code for primary or multimodal sensory information (Bian et al, 2008), probably relevant for the modulation of feeding behavior (McDonald, 1998;Berthoud, 2002).…”

“…Afferent excitatory pathways to this subnucleus use glutamate as neurotransmitter to code for primary or multimodal sensory information (Bian et al, 2008), probably relevant for the modulation of feeding behavior (McDonald, 1998;Berthoud, 2002). Besides, glutamate was found in almost 70% of all ejaculation-activated cells in the MePD (Simmons and Yahr, 2003), which could enhance the activity of efferent pathways that release gama-aminobutyric acid to inhibit or disinhibit specific hypothalamic targets and allow behavioral displays in rodents (Choi et al, 2005).…”