The medial preoptic area modulates the increase in plasma glucose and free fatty acid mobilization induced by acute cold exposure.
The effect of cold exposure (0 degrees C, 1 h) on free fatty acid (FFA) mobilization and plasma glucose was studied in freely moving male rats injected with adrenergic blockers (phentolamine or propranolol) into the medial preoptic area (MPOA). The rats were implanted with chronic jugular catheters for blood sampling and with unilateral intracerebral cannulas placed just above the MPOA. Blood samples were taken 2 min before and 10, 20, 40 and 60 min after cold exposure. After cold exposure plasma glucose and plasma FFA levels rose rapidly, reaching a peak at 20 min post-stimulus. Previous administration of phentolamine (50 nmol), but not propranolol (100 nmol), into the MPOA blocked the glycemic response to cold exposure. On the other hand, previous administration of propranolol, but not phentolamine, into the MPOA blocked the increased FFA mobilization in response to cold exposure. On the basis of these results, we propose that MPOA alpha-adrenergic synapses relay impulses activating the sympathetic outflow expressed by neurally mediated hyperglycemia, and beta-adrenergic synapses relay impulses activating the sympathetic outflow to the adipose tissue, increasing FFA acid mobilization.
Ferreira
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ML
Department of Physiology and Biophysics, Institute of Biological Science, Federal University of Minas Gerais, Belo Horizonte, Brazil.
Marubayashi
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U
Coimbra
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D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D019540:Area Under Curve; D001786:Blood Glucose / Q000378:metabolism*; D003080:Cold Temperature / Q000009:adverse effects*; D005230:Fatty Acids, Nonesterified / Q000378:metabolism*; D008297:Male; D009475:Neurons, Afferent / Q000502:physiology; D009638:Norepinephrine / Q000502:physiology; D010646:Phentolamine / Q000494:pharmacology; D011301:Preoptic Area / Q000502:physiology*; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar
D000317:Adrenergic alpha-Antagonists; D000319:Adrenergic beta-Antagonists; D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D011433:Propranolol; D009638:Norepinephrine; D010646:Phentolamine