Participation of glutamic acid in the catecholamines release from the amygdala of rabbits

Abstract

Glutamic acid (Glu), as the most stimulating neurotransmitter, occurs in almost all structures of the central nervous system (CNS). Especially high concentrations are found in the structures of the motivational system (hypothalamus, hippocampus, amygdala, prefrontal cortex – mPFC) and the motor system (striatum, caudate nucleus, pallidum). Glu is also found in the autonomic nervous system (ANS), as well as in peripheral tissues and organs (in the adrenal glands, especially important in stress; the hypothalamic-pituitary-adrenal axis – HPA axis). Catecholamines (CA), including dopamine (DA), norepinephrine (NE), and/or epinephrine (E), are major neurotransmitters that mediate various CNS functions, such as motor control, cognition, emotion, memory processing, pain, stress, and endocrine modulation. The aim of the study was to investigate the in vitro effect of different concentrations of Glu (5, 50, and 200 μM in a volume of 1 ml of Krebs medium) on CA release from rabbit amygdala sections collected after decapitation of 12-week-old female rabbits. The same piece of tissue was transferred every 30 minutes to successive incubation wells containing Glu in an appropriate dose. The medium collected from the wells after 30, 60, and 90 minutes of incubation was frozen until DA, NE, and E analyses were performed by the RIA method. The results showed that Glu differently affected CA release from the amygdala. Generally, an inhibitory effect of Glu on CA release from the amygdala was observed. It was surprising to find the highest concentration of E in the amygdala compared to NA and even DA.