Characterization of the norepinephrine-activation of adenylate cyclase suggests a role in memory affirmation pathways. Overexposure to epinephrine inactivates adenylate-cyclase,a causal pathway for stress-pathologies

TL;DR

This study explores how norepinephrine activates adenylate cyclase in rat brain membranes, highlighting its role in short-term memory pathways and how overexposure to epinephrine can inactivate the enzyme, potentially leading to stress-related pathologies.

Contribution

It reveals the ionic magnesium dependence of adenylate cyclase activation by norepinephrine and how prolonged epinephrine exposure inactivates the enzyme, linking it to stress and memory mechanisms.

Findings

Mg2+ is essential for norepinephrine-induced AC activation

Prolonged epinephrine exposure inactivates AC, suggesting stress pathology mechanisms

AC activity is modulated by ionic and metabolic factors like free ATP4-

Abstract

Incubation with noradrenaline (norepinephrine) of isolated membranes of rat's brain corpus striatum and cortex, showed that ionic-magnesium (Mg2+) is required for the neurotransmitter activatory response of Adenylate Cyclase [ATP pyrophosphate-lyase (cyclizing), (EC 4.6.1.1)], AC.An Mg2+-dependent response to the activatory effects of adrenaline, and subsequent inhibition by calcium, suggest capability for a turnover, associated with cyclic changes in membrane potential and participation in a short term-memory pathway.In the cell, the neurotransmitter by activating AC generates intracellular cyclic AMP. Calcium entrance in the cell inhibits the enzyme. The increment of cyclic AMP activates kinaseA and their protein phosphorylating activity, allowing a long term memory pathway. Hence, consolidating neuronal circuits, related to emotional learning and memory affirmation.The activatory effect relates to an enzyme-noradrenaline complex which may participate on the physiology of the fight or flight response, by prolonged exposure. However, the persistence of an unstable enzyme complex turns the enzyme inactive. Effect concordant, with the observation that prolonged exposure to adrenaline, participate in the etiology of stress triggered pathologies. At the cell physiological level AC responsiveness to hormones could be modulated by the concentration of Chelating Metabolites. These ones produce the release of free ATP4-, a negative modulator of AC and the Mg2+ activated insulin receptor tyrosine kinase (IRTK). Thus, allowing an integration of the hormonal response of both enzymes by ionic controls. This effect could supersede the metabolic feedback control by energy-charge. Accordingly, maximum hormonal response of both enzymes, to high Mg2+ and low free ATP4-, allows a correlation with the known effects of low caloric intake increasing average life expectancy.