The effect of stress on the galaninergic system in the rat adenohypophysis: mRNA expression and immunohistochemistry of galanin receptors

The neuropeptide galanin is a widely distributed neurotransmitter/neuromodulator that regulates a variety of physiological processes and also participates in the regulation of stress responses. The effect of stress is dependent on the activity of the hypo-thalamic-adenohypophyseal-adrenal axis. Although the adenohypophysis is a crucial part of this axis, galanin peptides and their receptors have not yet been identified in this part of the pituitary after activation of the stress response. Since there are many controversies about the occurrence of individual galanin receptor subtypes in the adenohypophysis under basal conditions, we decided to verify their presence immunohistochemically, and we clearly demonstrated that the adenohypophysis expresses neuropeptides galanin, galanin-like peptide, and subtypes of galanin receptors GalR1, GalR2 and GalR3. The specificity of the reactions was confirmed by Western blots for galanin receptors. Using real-time qPCR we also demonstrated the presence of three GalR subtypes, with the highest expression of GalR2. In addition, we tested the effect of stress. We found that acute stress did not induce any changes in the GalR2 expression, but increased expression of GalR1 and decreased that of GalR3. We confirmed the involvement of the galanin system in the stress regulation in the adenohypophysis.