In Biomedical Sciences Approved by

Growth hormone (GH) deficiency is associated with impaired learning and memory. One possible target for GH effects on memory is the hippocampus, a brain region containing GH receptors (GHRs). To determine if GH acutely alters hippocampal function, recombinant human GH (rhGH) was applied to in vitro rat hippocampal brain slices. Extracellular recordings were used to assess effects of GH on the field EPSP (fEPSP) and long-term potentiation (LTP) of the fEPSP. GHR expression was measured in GH-treated and control rat hippocampal slices using RT-PCR. The GH signaling pathway was investigated by studying the effect of GH on the fEPSP after block of Janus kinase (JAK) by tyrphostin AG 490, phosphoinositide-3-kinase (PI3-kinase) by wortmanin, and mitogen-activated/extracellular response protein kinase kinase (MEK) by U0126. To determine if protein synthesis is required, hippocampal slices were perfused with cycloheximide, a protein synthesis inhibitor. I examined the effects of GH on pharmacologically isolated N-methyl-D-aspartate receptor (NMDAR)-and α