Daily cycling of nitric oxide synthase (NOS) in the hippocampus of pigeons (C. livia)

Abstract

BackgroundNitric oxide synthase (NOS) is essential for the synthesis of nitric oxide (NO), a non-conventional neurotransmitter with an important role in synaptic plasticity underlying processes of hippocampus-dependent memory and in the regulation of biological clocks and circadian rhythms. Many studies have shown that both the NOS cytosolic protein content and its enzymatic activity present a circadian variation in different regions of the rodent brain, including the hippocampus. The present study investigated the daily variation of NOS enzymatic activity and the cytosolic content of nNOS in the hippocampus of pigeons.ResultsAdult pigeons kept under a skeleton photoperiod were assigned to six different groups. Homogenates of the hippocampus obtained at six different times-of-day were used for NOS analyses. Both iNOS activity and nNOS cytosolic protein concentrations were highest during the subjective light phase and lowest in the subjective dark phase of the circadian period. ANOVA showed significant time differences for iNOS enzymatic activity (p < 0.05) and for nNOS protein content (p < 0.05) in the hippocampus. A significant daily rhythm for both iNOS and nNOS was confirmed by analysis with the Cosinor method (p < 0.05). The present findings indicate that the enzymatic activity of iNOS and content of nNOS protein in the hippocampus of pigeons exhibit a daily rhythm, with acrophase values occurring during the behavioral activity phase.ConclusionsThe data corroborate the reports on circadian variation of NOS in the mammalian hippocampus and can be considered indicative of a dynamic interaction between hippocampus-dependent processes and circadian clock mechanisms.

Modulation of the NO-cGMP pathway has no effect on olfactory responses in the Drosophila antenna

“…As an example, circadian olfactory rhythms have been reported in insect antennae and are dependent on an autonomously oscillating regulatory gene network that establishes a daily olfactory rhythm (Tanoue et al, 2004;Schuckel et al, 2007;Flecke and Stengl, 2009;Schendzielorz et al, 2015). The involvement of NO as a key regulator establishing circadian rhythmicity is also well described in disparate models (Melo et al, 1997;Mitome et al, 2001;Tunçtan et al, 2002;Kunieda et al, 2008;Mitter et al, 2010;Plano et al, 2010;Machado-Nils et al, 2013;Gage and Nighorn, 2014), including Drosophila glia and neurons (Kozlov et al, 2020) and in sensory structures such as avian photoreceptors, which host circadian phase-dependent NOmediated regulation of ion channel activity (Ko et al, 2013), and may constitute a prospective antennal role for further investigation. Curiously, clock genes such as period (per) are present in a wide variety of cell types in the antenna including OSNs and their support cells and transcript abundance corresponds to daily rhythms of pheromone response in moths (Schuckel et al, 2007;Merlin et al, 2016).…”

Multi-Modal Regulation of Circadian Physiology by Interactive Features of Biological Clocks

“…Indeed, in other studies, the endogenous rhythms of eNOS activity in brain, kidney, testis, and lungs, as well as plasma NO levels, displayed 24 h rhythms under either LD or continuously lit conditions [ 183 , 184 ]. Furthermore, the rhythms of eNOS activity and expression were shown in the hippocampus of the pigeon and in isolated chick choroid, suggesting the evolutionary conservation of NO as a circadian-regulated signaling molecule [ 185 ].…”

Nitric oxide coordinates histone acetylation and expression of genes involved in growth/development and stress response

“…However, this reaction is only observed under low oxygen conditions (Gupta et al, 2010). NO production in mammals correlated with the expression and activity of NOS which is triggered by light (Ko et al, 2013;Machado-Nils et al, 2013). Although NOS enzymes have not been found in higher plants yet, it was demonstrated that NO can be produced in chloroplast via a NADPH-dependent oxidation of Larginine, which is the substrate of NOS.…”