J Korean Med Sci.  2013 Jun;28(6):946-950. 10.3346/jkms.2013.28.6.946.

Unique Hippocampal Changes and Allodynia in a Model of Chronic Stress

• Kim SH
• Moon IS
• Park IS

• KMID: 2158046
• DOI: http://doi.org/10.3346/jkms.2013.28.6.946

Abstract

Sustained stress can have numerous pathologic effects. There have been several animal models for chronic stress. We tried to identify the changes of pain threshold and hippocampus in a model of chronic stress. Male Sprague-Dawley rats were kept in a cage filled with 23degrees C water to a height of 2.2 cm for 7 days. Nociceptive thresholds, expressed in grams, were measured with a Dynamic Plantar Aesthesiometer. Golgi staining was used to identify hippocampal changes. To demonstrate how long allodynia was lasting, behavioral test was repeated daily on another experiment. Compared to control group, chronic stress group showed bilateral mechanical hyper-responsiveness on days 5 (P = 0.047) and 7 (P = 0.032). In general, dendrite atrophic changes within hippocampus of chronic stress model were much more prominent in comparison with control. Compared to control, decreased spine number (P < 0.001) and spine length (P < 0.001) on Golgi staining were seen in the hippocampus of animals with chronic stress. Bilateral mechanical hyperresponsiveness was recovered on day 19 in animals with chronic stress. Chronic stress may bring about central sensitization and hippocampal changes in rats.

Keyword

Stress; Hippocampus; Hyperalgesia; Models, Animal

MeSH Terms

Animals
Behavior, Animal
Disease Models, Animal
Hippocampus/*pathology
Hyperalgesia/*pathology
Male
Pain Threshold
Rats
Rats, Sprague-Dawley
Stress, Physiological

Figure

• 

  Fig. 1 Response to mechanical stimulation. Stress model showed bilateral mechanical hyper-responsiveness on day 5 and 7 compared to control. (Experiment I: n=5, group 1 and 2, respectively) The error bars indicate SD. Data from left and right hindpaws collapsed together for clarity of presentation. *P < 0.05.

• 

  Fig. 2 Spine number and length changes on Golgi staining within the hippocampus of rats. (A) No significant changes of spine number and length within the hippocampus of control rats (×100). The rectangle of left is enlarged on the right. (B) Significantly decreased spine number and length within hippocampus of stress model (×100). The rectangle of left is enlarged on the right. (C) Comparison of spine number per 20 µm between control (12.5) and stress (8.7) group in the hippocampus. (D) Comparison of spine length between control (1.31 µm) and stress (0.78 µm) group in the hippocampus (Experiment I: n = 5, group 1 and 2, respectively). Bars show the mean and SD. *P < 0.001 vs control.

• 

  Fig. 3 Line graph representing the median mechanical threshold from stress and control animals according to observation day. Bilateral mechanical hyper-responsiveness was recovered on day 19 (Experiment II: n = 10, group 1 and 2, respectively). Data from left and right hindpaws collapsed together for clarity of presentation. *P < 0.05, †P < 0.01, ‡P < 0.001.

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