Evidence for D2-Dopamine Receptors Modulating Noradrenaline Release in the Rat Frontal Cortex
The frontal cortex of the rat receives dopaminergic and noradrenergic nerve terminals from the ventral tegmental area and the locus coeruleus, respectively. Different categories of catecholamine receptors are present in this area, including alpha2-adrenoceptors and D1 and D2 dopamine (DA) receptors. However the location and the role of such receptors are not clear. Peripheral noradrenergic nerve terminals have both alpha2 and D2 presynaptic receptors, the stimulation of either ones resulting in the inhibition of noradrenaline (NA) release (see 1). In the central noradrenergic nerve terminals the presence of presynaptic alpha2-adrenoceptors has been shown in vitro by using brain slices and synaptosomes (2,3) and, more recently, by the use of the technique of brain dialysis in anesthetized rats (4). In the latter study the cortical outflow of NA was shown to be inhibited by clonidine, an alpha2-adrenoceptor agonist, and to be increased by idazoxan, a blocker of alpha2-adrenoceptors.
KeywordsFrontal Cortex Ventral Tegmental Area Locus Coeruleus Dopamine Autoreceptors Catecholamine Receptor
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