S. Arancibia et al., Acute stress and dexamethasone rapidly increase hippocampal somatostatin synthesis and release from the dentate gyrus hilus, HIPPOCAMPUS, 11(4), 2001, pp. 469-477
Somatostatin is a neuropeptide whose facilitatory action in the generation
of long-term potentiation (LTP) in the hippocampal dentate gyrus has been a
ssociated with memory processes. Since stress and memory seem to share some
neural pathways, we studied somatostatin release from dentate gyrus hilar
cells of the hippocampus in unanesthetized free-moving rats subjected to st
ress or dexamethasone treatments. In parallel, the number of dentate gyrus
hilar cells expressing somatostatin mRNA was quantified by nonradioactive i
n situ hybridization in these two experimental conditions.
Rats were stereotaxically implanted with a push-pull cannula in the dentate
gyrus hilar region. Animals were perfused 1 week later in basal or stress
(30 min immobilization stress) conditions. The other group was intraperiton
eally injected with the synthetic glucocorticoid dexamethasone (3 mg/kg b.w
.). Samples were collected every 15 min for somatostatin radioimmunoassay.
In parallel, in other groups of animals undergoing the same treatments, bra
ins were removed for in situ hybridization studies with an oligonucleotide
labeled with digoxigenin that recognizes somatostatin-14.
The results showed that stress induced a significant increase in somatostat
in release from dentate gyrus hilar cells 30-45 min after immobilization st
ress application. Dexamethasone-injected animals exhibited a similar respon
se 45 min after drug administration. In situ hybridization analysis reveale
d that the two treatments significantly increased the number of cells expre
ssing somatostatin mRNA in the hilar region.
In conclusion, somatostatin interneurons of the hippocampal hilar region ap
pear to be a novel stress stimulus target. Their rapid reactivity, expresse
d as modifications of both somatostatin release and number of cells express
ing somatostatin mRNA, provides an interesting model of neuronal plasticity
. Hippocampus 2001;11:469-477. (C) 2001 Wiley-Liss, Inc.