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Castration Decreases Single Cell Levels of mRNA Encoding Glutamic Acid Decarboxylase in the Diagonal Band of Broca and the Sexually Dimorphic Nucleus of the Preoptic Area
Author(s) -
Sagrillo Cathleen A.,
Selmanoff Michael
Publication year - 1997
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1046/j.1365-2826.1997.00630.x
Subject(s) - glutamate decarboxylase , medicine , diagonal band of broca , endocrinology , biology , median eminence , globus pallidus , nucleus , substantia innominata , preoptic area , piriform cortex , periventricular nucleus , castration , gabaergic , hypothalamus , amygdala , arcuate nucleus , neuroscience , central nervous system , basal ganglia , cholinergic neuron , inhibitory postsynaptic potential , biochemistry , hormone , enzyme
Using quantitative in situ hybridization histochemistry (ISHH), we determined the effect of castration on single cell levels of glutamic acid decarboxylase (GAD) mRNA in discrete hypothalamic regions of the male rat brain associated with the control of gonadotropin secretion. A 48‐base oligodeoxynucleotide probe was used to detect with equal affinity the two isoforms of GAD message, GAD 65 and GAD 67 . GAD message also was quantitated in a number of selected areas of the brain to contrast GAD gene expression amongst several populations of GABAergic neurons. Comparison of 11 brain regions demonstrated a 9.3‐fold range in the quantity of single cell GAD mRNA with levels being highest in the amygdala and the diagonal band of Broca, moderate in the piriform cortex, caudate nucleus, substantia innominata, globus pallidus, cingulate cortex and medial septal nucleus, and lowest in the lateral septal nucleus and the medial preoptic nucleus (MPN). Castration markedly reduced single cell GAD mRNA levels in the DBB and the MPN, two discrete hypothalamic structures known to contain dendritic fields, cell bodies, and axons of GnRH neurons projecting to the median eminence. A striking finding was a dense core of steroid‐sensitive GABAergic neurons within the MPN comprising the sexually dimorphic nucleus of the preoptic area (SDN‐POA). Similar to the MPN as a whole, the amount of GAD mRNA expressed by cells in the SDN‐POA of sham operated control rats was greater than in castrated animals. GAD mRNA levels were inversely related to serum LH titers, suggesting a role for these neurons in the mechanism controlling gonadal steroid negative feedback on LH secretion. This report provides the basis for future work to determine if GAD 65 , GAD 67 or whether both isoforms are affected by gonadal steroid input.