Role of the Dopaminergic Neurotransmission in the Central Nucleus of Amygdala in Cardiovascular Changes Induced by Intrategmental Microinjection of DiMe-C7

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Many evidences have been shown to support an involvement of central mesocorticolimbic dopaminergic system in stress response. The stimulation of the mesocorticolimbic dopaminergic system by local microinjection of the substance P analogue DiMe-C7 (10 fmol) into the ventral tegmental area (VTA) caused increases in the mean arterial blood pressure (MAP) and heart rate (HR) in chloral hydrate anaesthetized rats. The pressure response was associated with the increases in the dopamine (DA) level in the central nucleus of amygdala (CeA; 140  6 %), the plasma vasopressin (VP) concentration (8.6 ± 1.0 vs. 22.5 ± 2.4 pg/ml) and the inhibition of baroreflex response (BRR; 66 ± 5 %). Bilateral pretreatment with the DA antagonist, haloperidol, into the CeA totally blunted the increases of MAP, HR, and the inhibition of BRR after DiMe-C7 microinjection. However, the pretreatment had no effect on the increase of plasma VP concentration. Local application of DA agonist into the CeA had no effect on the AP, HR, and the plasma VP concentration, but significantly inhibited BRR (49 ± 2 %). Our results suggested that the DA neurotransmission in the CeA is involved in the elevation of the AP and HR after intrategmental DiMe-C7 injection, which is possibly through the inhibition of the BRR.