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Decreased expression of the mRNA for somatostatin in the periventricular nucleus of depression-model rats
K Zhang1, K Hamanaka, I Kitayama
1Department of Psychiatry, Mie University School of Medicine, Tsu, Japan. zhangkai@clin.medic.mie-u.ac.jp
Abstract:
Expression of the mRNA for somatostatin (SRIF) in the periventricular nucleus (PeN), the level of SRIF in the stalk-median eminence (SME) and the concentration of growth hormone (GH) in the plasma were examined in depression-model rats in an attempt to confirm the hypothesis that SRIF neurons in the hypothalamus are hypofunctional in this model. We exposed male Wistar rats to intermittent walking stress for two weeks and then we measured their spontaneous running activity for 12 days. We divided the rats into a depression-model group and a partial-recovery group according to the spontaneous running activity of each rat after the termination of exposure to stress. Expression of SRIF mRNA in the PeN of the hypothalamus was monitored by in situ hybridization and relative levels were determined with an image analysis system. The relative level of expression of SRIF mRNA in the PeN was lower in rats in the depression-model group than in the control group and the partial-recovery group. The level of SRIF in the SME was lower and the plasma concentration of GH was higher in the depression-model group than in the other groups. Our findings suggest that reduced expression of mRNA for SRIF in the PeN might be associated with the pathophysiology of rats with this particular model of depression.
Insights
Rats modeled for depression showed reduced somatostatin (SRIF) mRNA expression in the hypothalamus. This suggests hypothalamic SRIF neurons may be hypofunctional in depression pathophysiology.
Area of Science:
- Neuroscience
- Endocrinology
- Psychiatry
Background:
- Hypothalamic somatostatin (SRIF) neurons play a role in regulating various physiological functions.
- Altered SRIFergic activity has been implicated in mood disorders, but its specific role in depression models requires further investigation.
Purpose of the Study:
- To investigate the functional status of hypothalamic SRIF neurons in a rat model of depression.
- To examine the relationship between SRIF expression, SRIF levels, and growth hormone (GH) concentration in this depression model.
Main Methods:
- Male Wistar rats were subjected to intermittent walking stress to induce a depression model.
- Spontaneous running activity was measured to categorize rats into depression and partial-recovery groups.
- In situ hybridization was used to quantify SRIF mRNA expression in the periventricular nucleus (PeN).
- SRIF levels in the stalk-median eminence (SME) and plasma GH concentrations were measured.
Main Results:
- Rats in the depression model exhibited significantly lower SRIF mRNA expression in the PeN compared to control and partial-recovery groups.
- The depression model group showed reduced SRIF levels in the SME.
- Plasma GH concentrations were elevated in the depression model group.
Conclusions:
- Reduced SRIF mRNA expression in the PeN is associated with the pathophysiology of this rat model of depression.
- These findings support the hypothesis of hypothalamic SRIF neuron hypofunctionality in depression.
- Altered SRIFergic signaling may contribute to neuroendocrine dysregulation observed in depression.
