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Footshock affects heart and brain MAO and MAO inhibitory activity and open field behavior in rats
A P Lemoine1, I Armando, J C Brun
1Laboratorio de Neurofisiologia y Fisiologia del Comportamiento, IBYME, CONICET, Buenos Aires, Argentina.
Abstract:
This study examined the effects, after 1 min or 2 hr, of one footshock session on the activity of MAO in rat heart and brain, the MAO inhibitory activity of these tissues, and the animal's behavior in an open field. Internal ambulation was reduced at both times; the lowest score was registered at 1 min. The number of boluses emitted during the test was higher in the group tested at 2 hr than in the other groups. One min after shocks MAO activity in heart and brain was decreased. In the heart MAO was still decreased 2 hr later, then reaching the lowest levels, while at that time, brain MAO was not different from controls. When assayed separately (MAO A and B), only the A form was found to change. MAO inhibitory activity in heart was increased at both times, the highest activity observed 2 hr after footshock. Brain MAO inhibitory activity was increased only in the 1-min group. Ex vivo competition experiments with clorgyline suggested presence in vivo of a reversible MAO inhibitor. The time-dependent response to stress of both MAO activity and MAO inhibitory activity in the tissues correlates with the responses observed in the open field test. These findings suggest that the observed biochemical changes might be related to increased autonomic activity and to the state of fear and anxiety evoked by the stressful procedure.
Insights
Stress from footshock significantly alters monoamine oxidase (MAO) activity and MAO inhibitory activity in rat heart and brain. These biochemical changes correlate with behavioral responses, suggesting a link to autonomic activity, fear, and anxiety.
Area of Science:
- Neuroscience
- Biochemistry
- Pharmacology
Background:
- Stress impacts physiological and behavioral responses.
- Monoamine oxidase (MAO) plays a crucial role in neurotransmitter metabolism.
- Understanding MAO's role in stress is vital for neurological and psychiatric research.
Purpose of the Study:
- To investigate the effects of acute stress (footshock) on MAO activity and MAO inhibitory activity in rat heart and brain.
- To correlate biochemical changes with behavioral alterations in an open field test.
Main Methods:
- Rats were subjected to a single footshock session.
- MAO activity and MAO inhibitory activity were measured in heart and brain tissues at 1 min and 2 hr post-stress.
- Behavioral analysis was conducted using an open field test.
- MAO A and B isoforms were assayed separately.
- Ex vivo competition experiments were performed.
Main Results:
- Footshock reduced ambulation and increased bolus emission in rats.
- MAO activity decreased in heart and brain at 1 min post-stress; heart MAO remained decreased at 2 hr, while brain MAO normalized.
- MAO A isoform was primarily affected.
- MAO inhibitory activity increased in the heart at both time points and in the brain at 1 min.
- Evidence suggested the presence of a reversible MAO inhibitor in vivo.
Conclusions:
- Acute stress induces time-dependent changes in MAO activity and inhibitory activity in rat tissues.
- These biochemical alterations correlate with behavioral changes observed in the open field test.
- Findings suggest a relationship between stress-induced MAO modulation, autonomic activity, and emotional states like fear and anxiety.