We previously reported that injection of PGF2α into the third cerebral ventricle produces hyperglycemia and hyperthermia associated with catecholamine secretion in anesthetized rats. We have also studied the potency of catecholamine secretion induced by injecting PGE2 or PGF2α into the third cerebral ventricle and the effect of the GABA-selective agonist, muscimol, on the catecholamine secretion induced by PGE2 or PGF2α. Administration of 50 μg of PGE2 into the third cerebral ventricle increased norepinephrine secretion to a greater extent than the same dose of PGF2α, whereas the latter increased epinephrine secretion to a greater degree. These effects pararelled the potencies of the hyperglycemic and hyperthermic effects of PGF2α and PGE2, respectively. Simultaneous injection of 2.5 nmol of muscimol into the third cerebral ventricle with 50μg of PGF2α or PGE2 completely suppressed epinephrine and norepinephrine secretion induced by PGF2α or PGE2. These findings suggest that central PGF2α and PGE2 stimulate epinephrine and norepinephrine secretion with different potencies, and that brain GABAA receptors suppress catecholamine secretion induced by PGF2α or PGE2.
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