Stress modulates instrumental action in favor of habitual stimulus-response processes that are insensitive to changes in outcome value and at the expense of goal-directed action-outcome processes. The neuroendocrine mechanism underlying this phenomenon is unknown. Here, we tested the hypothesis that concurrent glucocorticoid and noradrenergic activity bias instrumental behavior toward habitual ...

The selectivity and specificity of CH-38083 [7,8-(methylenedioxi)-14-alpha-hydroxyalloberbane HCl], a berbane derivative for alpha adrenoceptors has been studied and compared with yohimbine and idazoxan in peripheral tissues and in the central nervous system. In isolated tissue experiments CH-38083 was a competitive antagonist at presynaptic alpha-2 adrenoceptors on the axon terminals of the ra...

Intravenous sodium lactate infusions or the noradrenergic agent yohimbine reliably induce panic attacks in humans with panic disorder but not in healthy controls. However, the exact mechanism of lactate eliciting a panic attack is still unknown. In rats with chronic disruption of GABA-mediated inhibition in the dorsomedial hypothalamus (DMH), achieved by chronic microinfusion of the glutamic ac...

Increased vascular resistance during systemic nitric oxide synthase (NOS) inhibition is dependent on adrenergic vasoconstriction. This study tested the hypothesis that increased vascular sensitivity to adrenergic agonists contributes to this vasoconstriction. Superior mesenteric arteries and thoracic aortae from male Sprague-Dawley rats drinking water containing N ω-nitro-l-arginine (l-NNA; 14 ...

The effects of pharmacological modulation of adrenergic receptors on colonic motor and sensory function are unclear. We studied 40 healthy volunteers in a single-blind design; 12 received saline, and the remaining 28 received either clonidine, yohimbine, phenylephrine, or ritodrine. A barostat-manometric assembly in the left colon recorded drug effects on fasting and postprandial motor function...

Several studies have shown that noradrenergic mechanisms are important for locomotion. For instance, L-dihydroxyphenylalanine (L-DOPA) can initiate "fictive" locomotion in immobilized acutely spinalized cats and alpha(2)-noradrenergic agonists, such as 2,6,-dichloro-N-2-imidazolidinylid-enebenzenamine (clonidine), can induce treadmill locomotion soon after spinalization. However, the activation...

Platelets possess a2-adrenergic and serotonergic (5-hydroxytryptamine) receptors which are thought to mediate the in vitro proaggregatory effects of epinephrine and serotonin, respectively. However, their importance in platelet aggregation in vivo is uncertain. In the present study, we evaluate the ability of yohimbine and ketanserin, relatively selective o2-adrenergic and serotonin antagonists...

BACKGROUND Amitraz, an insecticide used to prevent tick and mite infestation of cattle, crops and dogs, is an alpha2-adrenergic receptor agonist that inhibits GnRH release and the ovulatory LH surge in rats. Noradrenalin, the physiological ligand for adrenergic receptors, inhibits progesterone production by IVF-derived granulosa cells, but the effects of amitraz are unknown. METHODS Luteinize...

Extinction of classically conditioned fear, like its acquisition, is active learning, but little is known about its molecular mechanisms. We recently reported that temporal massing of conditional stimulus (CS) presentations improves extinction memory acquisition, and suggested that temporal spacing was less effective because individual CS exposures trigger two opposing processes: (1) fear extin...

Adrenoceptor-mediated Cl- transport in cultured rabbit corneal endothelium was examined using a Cl(-)-sensitive fluorescent dye. The intracellular Cl- concentration ([Cl-]i) in the endothelial cells was estimated to be about 30 mM. Noradrenaline (0.001-0.1 mM) transiently decreased the [Cl-]i in a dose-dependent manner. Such a decrease in [Cl-]i was completely antagonized by pretreatment with t...