The Activation of β2-Adrenergic Receptors in Naïve Rats Causes a Reduction of Blood Glutamate Levels: Relevance to Stress and Neuroprotection
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This study examines the effects of the activation of β1 and β2-adrenergic receptors on glutamate homeostasis in the blood of naïve rats. Forty five male Sprague–Dawley rats were randomly assigned into one of seven treatment groups that were treated with various β-adrenergic receptor agonist and antagonist drugs. Blood glutamate levels were determined at t = 0, 30, 60, 90, and 120 min. The activation of β1 and β2-adrenergic receptors via isoproterenol hydrochloride administration produced a marked sustained decrease in blood glutamate levels by 60 min after treatment (ANOVA, t = 60, 90 min: P < 0.05, t = 120 min: P < 0.01). Pretreatment with propranolol hydrochloride (a non-selective β-adrenergic receptor blocker) or butaxamine hydrochloride (a selective β2-adrenergic receptor blocker) occluded the isoproterenol-mediated decrease in blood glutamate levels. Propranolol alone had no effect on blood glutamate levels. Selective β1-adrenergic receptor blockade with metoprolol resulted in decreased blood glutamate levels (ANOVA, t = 90 min: P < 0.05, t = 120 min: P < 0.01). Butaxamine hydrochloride alone resulted in a delayed-onset increase in glutamate levels (ANOVA, t = 120 min: P < 0.05). The results suggest that the activation of β2 receptors plays an important role in the homeostasis of glutamate in rat blood.
Keywordsβ2-Adrenergic receptors Glutamate Recovery Traumatic brain injury
The authors thank Dorit Reymond for her superb technical assistance. This work was supported in part by grants to VIT from the Nella and Leon Benoziyo Center for Neurological Diseases; Braintact Ltd., the Irwin Green Fund for Studying the Development of the Brain, the Carl and Micaela Einhorn-Dominic Institute for Brain Research. VIT is the incumbent of the Louis and Florence Katz-Cohen Chair of Neuropharmacology.
Conflict of Interest
V.I.T received a grant from Braintact Ltd., as well as consultancy fees.
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