Long- term enhancements in antidepressant efficacy and neurogenesis: Effects of intranasal co- administration of neuropeptide Y 1 receptor (NPY1R) and galanin receptor 2 (GALR2) agonists in the ventral hippocampus

Abstract

This study evaluates the sustained antidepressant- like effects and neurogenic potential of a 3- day intranasal co- administration regimen of galanin receptor 2 (GALR2) agonist M1145 and neuropeptide Y Y1 receptor (NPY1R) agonist [Leu31, Pro34]NPY in the ventral hippocampus of adult rats, with outcomes ana-lyzed 3 weeks post- treatment. Utilizing the forced swimming test (FST), we found that this co- administration significantly enhances antidepressant- like behaviors, an effect neutralized by the GALR2 antagonist M871, highlighting the syner-gistic potential of these neuropeptides in modulating mood- related behaviors. In situ proximity ligation assay (PLA) indicated a significant increase in GALR2/NPYY1R heteroreceptor complexes in the ventral hippocampal dentate gyrus, suggesting a molecular basis for the behavioral outcomes observed. Moreover, proliferating cell nuclear antigen (PCNA) immunolabeling revealed increased cell proliferation in the subgranular zone of the dentate gyrus, specifically in neuroblasts as evidenced by co- labeling with doublecortin (DCX), without affect-ing quiescent neural progenitors or astrocytes. The study also noted a significant uptick in the number of DCX- positive cells and alterations in dendritic morphol-ogy in the ventral hippocampus, indicative of enhanced neuronal differentiation and maturation.