Modulatory effect of olanzapine on SMIM20/phoenixin, NPQ/spexin and NUCB2/nesfatin-1 gene expressions in the rat brainstem

Abstract

Background: Phoenixin, spexin and nesfatin-1 belong to a family of newly discovered multifunctional neuropeptides that play regulatory roles in several brain structures and modulate the activity of important neural networks. However, little is known about their expression and action at the level of brainstem. The present work was, therefore, focused on gene expression of the aforementioned peptides in the brainstem of rats chronically treated with olanzapine, a second generation antipsychotic drug.

Methods: Studies were carried out on adult, male Sprague-Dawley rats that were divided into 2 groups: control and experimental animals treated with olanzapine (28-day-long intraperitoneal injection, at dose 5 mg/kg daily). All individuals were killed under anesthesia and the brainstem excised. Total mRNA was isolated from homogenized samples of both structures and the RT-PCR method was used for estimation of related SMIM20/phoenixin, NPQ/spexin and NUCB2/nesfatin-1 gene expression.

Results: Long-term treatment with olanzapine is reflected in qualitatively different changes in expression of examined neuropeptides mRNA in the rat brainstem. Olanzapine significantly decreased NPQ/spexin mRNA expression, but increased SMIM20/phoenixin mRNA level in the rat brainstem; while NUCB2/nesfatin-1 mRNA expression remained unchanged.

Conclusions: Olanzapine can affect novel peptidergic signaling in the rat brainstem. This may cautiously suggest the presence of an alternative mode of its action.

Keywords: Brainstem; Nesfatin-1; Olanzapine; Phoenixin; Spexin.

Fig. 1

Schematic representation of the experimental method (a). The brainstem segments (− 8.7 to − 12.6 mm from bregma, a, b) were excised, total mRNA was isolated and the Real-Time PCR method was used for estimation of related SMIM20/phoenixin, NPQ/spexin and NUCB2/nesfatin-1 gene expressions. Tissue samples contained the main brainstem nuclei including aminergic and peptidergic perikarya. bs brainstem, ce cerebellum. Structural figures based on modified brain sections taken from the standard Paxinos and Watson The Rat Brain Atlas [47]

Fig. 2

Relative mRNA expression of SMIM20/phoenixin, NUCB2/nesfatin-1 and NPQ/spexin in the rat brainstem after long-term olanzapine administration. Number of animals per group (n = 5). Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used as a reference gene. Values are expressed as means ± SEM. Differences between experimental groups were analyzed using one-way ANOVA followed by Tukey’s post hoc test and they were considered significant at p ≤ 0.01 (asterisks)