Expression of preprogalanin mRNA following acute and chronic restraint stress in brains of normotensive and hypertensive rats

Abstract

Exposure to stress is known to induce widespread changes in the central nervous system (CNS) involving multiple neuropeptides. The neuropeptide galanin has been implicated in the central response to different stressors; however, the role of galanin in the response to restraint stress has not been reported. Therefore, this study utilised in situ hybridisation histochemistry to observe the effects of acute and chronic restraint stress on preprogalanin (preproGAL) mRNA expression in the CNS of normotensive (Wistar Kyoto; WKY) and Spontaneously Hypertensive (SHR) rats. Rats were exposed to 1 h of restraint for 0 (control), 1, 3, 5, or 10 consecutive days, and central preproGAL mRNA expression following these restraint periods was compared between strains. Significant differences in the basal expression of preproGAL mRNA were detected, with expression decreased by ∼50% in the supraoptic nucleus (SON; P<0.01) and increased by ∼100% in the rostral ventrolateral medulla (RVLM; P<0.05) of SHR when compared to WKY. Following acute restraint (1 session), preproGAL mRNA expression was significantly increased by ∼135% in the central nucleus of the amygdala (CeA; P<0.05) in WKY. In SHR, significant increases of up to 300% were observed in the CeA ( P<0.01) and SON ( P<0.05) following chronic restraint (up to 10 days). In addition, expression of preproGAL mRNA was significantly decreased in the locus coeruleus (LC) of SHR following acute restraint (1 session) ( P<0.05). These results provide the first evidence that both acute (LC) and chronic (CeA, SON) restraint stress is associated with alterations in preproGAL mRNA expression. As such, the present study provides further evidence linking neurons containing galanin with the central response to restraint stress.