Intracerebroventricular administration of growth hormone induces morphological changes in pyramidal neurons of the hippocampus and prefrontal cortex in adult rats

Abstract

A growing body of evidence suggests that growth hormone (GH) affects synaptic plasticity at both the molecular and electrophysiological levels. However, unclear is whether plasticity that is stimulated by GH is associated with changes in neuron structure. This study investigated the effect of intracerebroventricular (ICV) administration of GH on the morphology of pyramidal neurons of the CA1 region of the dorsal hippocampus and layer III of the prefrontal cortex. Male Wistar rats received daily ICV injections of GH (120 ng) for 7 days, and they were euthanized 21 days later. Changes in neuronal morphology were evaluated using Golgi-Cox staining and subsequent Sholl analysis. GH administration increased total dendritic length in the CA1 region of the dorsal hippocampus and prefrontal cortex. The Sholl analysis revealed an increase in dendritic length of the third to eighth branch orders in the hippocampus and from the third to sixth branch orders in the prefrontal cortex. Interestingly, GH treatment increased the density of dendritic spines in both brain regions, favoring the presence of mushroom-like spines only in the CA1 hippocampal region. Our results indicated that GH induces changes in the length of dendritic trees and the density of dendritic spines in two high-plasticity brain regions, suggesting that GH-induced synaptic plasticity at the molecular and electrophysiological levels may be associated with these structural changes in neurons.

Pregnancies alters spine number in cortical and subcortical limbic brain regions of old rats

“…Several reports suggest that GH levels reduce with aging (Ashpole, Sanders, Hodges, Yan, & Sonntag, ; Sattler, ). A recent report for our group demonstrated that GH induced an increase in dendritic length in layer 3 of the PFC and CA1 of the dorsal hippocampus (Olivarez‐Hernández et al, ). In addition, cognitive functions decline during aging and several reports have demonstrated an increase in the extracellular levels of glutamate, that in high levels may induce neurotoxicity (Brewer, ; Choi et al, ; Zoia et al, ) and also alter mitochondrial function (Avila et al, ; Choi et al, ; Plaitakis, Zaganas, & Spanaki, ), which results in reduced dendritic length (Jia et al, ).…”

Treatment with Growth Hormone (GH) Increased the Metabolic Activity of the Brain in an Elder Patient, Not GH-Deficient, Who Suffered Mild Cognitive Alterations and Had an ApoE 4/3 Genotype

“…This may indicate that treatment with the hormone has induced an increase in the number of neurons in this area, as we and others have shown in rats [ 10 , 11 ]. Another possibility is that GH has induced the outbreak of dendritic spines and changes in the length and density of pre-existing dendrites in the hippocampus, as has been shown to occur after intracerebroventricular administration of the hormone in adult rats [ 42 ]. If we could have used 3′-deoxy-3′-[18F] fluoro- l -thymidine instead of FDG, we could have detected whether the changes observed in PET-SCAN were due or not to adult neurogenesis, as a study has shown in adult rats [ 43 ].…”

Growth Hormone (GH) Administration Increases the Metabolic Activity of the left Hippocampus in an Elder Patient with Cognitive Disorders

“…The second possibility is that GH induced sprout of dendritic spines and changes in the lenght and density of pre-existing dendrites in the hippocampus, as it has been demonstrated after intracerebroventricular administration of the hormone in adult rats [29]. However, this possibility does not exclude the one indicated above.…”