Chronic Lithium Treatment Alters NMDA and AMPA Receptor Synaptic Availability and Dendritic Spine Organization in the Rat Hippocampus

Title:Chronic Lithium Treatment Alters NMDA and AMPA Receptor Synaptic Availability and Dendritic Spine Organization in the Rat Hippocampus

Volume: 22 Issue: 12

Author(s): Lucia Caffino, Giorgia Targa, Anne Stephanie Mallien, Francesca Mottarlini, Beatrice Rizzi, Judith R. Homberg, Peter Gass and Fabio Fumagalli*

Affiliation:

• Department of Pharmacological and Biomolecular Sciences ‘Rodolfo Paoletti’, Università degli Studi di Milano, Via Balzaretti 9, 20133, Milan, Italy

Abstract:

Background: The mechanisms underlying the action of lithium (LiCl) in bipolar disorder (BD) are still far from being completely understood. Previous evidence has revealed that BD is characterized by glutamate hyperexcitability, suggesting that LiCl may act, at least partially, by toning down glutamatergic signaling abnormalities.

Objective: In this study, taking advantage of western blot and confocal microscopy, we used a combination of integrative molecular and morphological approaches in rats exposed to repeated administration of LiCl at a therapeutic dose (between 0.6 and 1.2 mmol/l) and sacrificed at two different time points, i.e., 24 hours and 7 days after the last exposure.

Results: We report that repeated LiCl treatment activates multiple, parallel, but also converging forms of compensatory neuroplasticity related to glutamatergic signaling. More specifically, LiCl promoted a wave of neuroplasticity in the hippocampus, involving the synaptic recruitment of GluN2A-containing NMDA receptors, GluA1-containing AMPA receptors, and the neurotrophin BDNF that are indicative of a more plastic spine. The latter is evidenced by morphological analyses showing changes in dendritic spine morphology, such as increased length and head diameter of such spines. These changes may counteract the potentially negative extra-synaptic movements of GluN2B-containing NMDA receptors as well as the increase in the formation of GluA2-lacking Ca²⁺-permeable AMPA receptors.

Conclusion: Our findings highlight a previously unknown cohesive picture of the glutamatergic implications of LiCl action that persist long after the end of its administration, revealing for the first time a profound and persistent reorganization of the glutamatergic postsynaptic density receptor composition and structure.

Cite this article as:

Caffino Lucia, Targa Giorgia, Mallien Stephanie Anne, Mottarlini Francesca, Rizzi Beatrice, Homberg R. Judith, Gass Peter and Fumagalli Fabio*, Chronic Lithium Treatment Alters NMDA and AMPA Receptor Synaptic Availability and Dendritic Spine Organization in the Rat Hippocampus, Current Neuropharmacology 2024; 22 (12) . https://dx.doi.org/10.2174/1570159X21666230913144420