Interactions between neuropeptide Y and alpha 2-adrenoceptors in selective rat brain regions.
Neuropeptide Y significantly reduced the potassium-stimulated release of [3H]norepinephrine [( 3H]NE) from slices of rat hippocampus, hypothalamus and frontal cortex but not from slices of parieto-occipital cortex. The NPY-induced inhibition of [3H]NE release from frontal cortical slices was concentration dependent, reaching statistical significance at 10 nM. The alpha 2-adrenoceptor partial agonist, clonidine, also reduced the potassium-stimulated release of [3H]NE. The combination of NPY and clonidine in hippocampal slices produced a greater reduction of stimulated [3H]NE release than either of the two compounds alone, suggesting a potentiation of their activity, whereas in frontal cortical slices, the effect was additive. When NPY and clonidine were added to frontal cortical slices, they independently produced a significant concentration-dependent reduction in forskolin-stimulated cAMP accumulation. However, NPY and clonidine combined did not produce a further reduction in forskolin-induced cAMP accumulation than either compound when used alone. These results suggest that the ability of NPY to potentiate alpha 2-adrenoceptor-induced inhibition of [3H]NE release in discrete brain regions does not depend on the reductions in cAMP.
Widdowson
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PS
Department of Psychiatry, Case Western Reserve University, Cleveland, OH.
Masten
T
T
Halaris
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D000818:Animals; D001921:Brain / Q000187:drug effects*; D003000:Clonidine / Q000494:pharmacology; D005576:Colforsin / Q000037:antagonists & inhibitors; D000242:Cyclic AMP / Q000096:biosynthesis; D066298:In Vitro Techniques; D008297:Male; D009478:Neuropeptide Y / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism; D011188:Potassium / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*
D009478:Neuropeptide Y; D011942:Receptors, Adrenergic, alpha; D005576:Colforsin; D000242:Cyclic AMP; D003000:Clonidine; D011188:Potassium; D009638:Norepinephrine