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Expression of Cx40 and Cx43 in dorsal horn of the spinal cord after exposure to chronic stress and castration

Introduction: Gap junctions are specialized intercellular connections between two adjacent cells formed of two hemichannels, one provided by each cell. Function of that connection is described as two-way passage enabling direct metabolic and electrical communication. Hemichannels can be activated by various changes in intracellular signalling, and hence have an influence on different physiological conditions, such as modulation of neuronal activity. Chronic stress represents the situation in which the organism is exposed to a stimulus over a long period of time with effects on the afferent pathway by the reflex reaction, mostly visibly through the condition known as neurological pain. The aim of this study was to determine whether the exposure to chronic stress affects protein expression of Connexins 40 and 43 in the dorsal horn of the spinal cord (SC), and if that change depends on sex hormones. Methods: Sprague-Dawley rats were orchidectomized (M-Orx), ovariectomized (F-Ovx) or sham (MSh or F-Sh) operated at the age of 13 months. At the age of 15 months three 10- day-sessions of sham (C) or chronic stress (S) were applied. The animals were sacrificed at the age of 17 and half months. The anterior thoracic SC tissue was embedded in paraffin and an immunohistochemistry protocol was applied for determination and quantification of Cx40 and Cx43 expression. Results: Expression of Cx40 in male groups decreased in response to chronic stress and castration compared to the chronic stress sham operated group (M-Orx-S vs. M-Sh-S P<0.01), while in female groups Cx40 expression increased after gonadectomy F-Ovx-S vs. F-Sh-S P<0.01. Expression of Cx43 was significantly higher in female than in male animals (P<0.05), but the influence of chronic stress and gonadectomy was not found. Discussion and conclusion: This insight into the expression of gap junctions in the dorsal horn of SC exposed to chronic stress may be crucial for understanding the formation of spinal neuronal circuits, which is supported through management of electrical and biochemical communication among some neurons and their surroundings with eventually significant influence on modulating neuronal activity.

chronic stress ; sex hormones ; spinal cord ; Cx40 ; Cx43

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