Adrenoreceptors metabolic effects

The catecholamines epinephrine and norepinephrine (adrenaline and noradrenaline) originate in the inner medullar region of the adrenal glands. Stimulation of the adrenal by the sympathetic nervous system leads to secretion of catecholamines into the bloodstream. In addition, adipose tissue is itself directly innervated by the sympathetic nervous system. Various types of metabolic stress trigger the sympathetic nervous system to release its neurotransmitter, norepinephrine, directly into adipose where its effects on the adipocyte are mediated by specific plasma membrane adrenoreceptors. Rapid reflex responses are primarily stimulated by the sympathetic nervous system, whereas more long-term (i.e., on the scale of hours, days, and weeks) and/or basal effects are subject to regulation by catecholamine secretion. 

Savaki, H. E., Kadekaro, M., Jehle, J., and Sokoloff, L., 1978, a- and p-adrenoreceptor blockers have opposite effects on energy metabolism on the central auditory system. Nature (London) 276 521-523. 

Considering that, studies have been developed to establish the toxicological profile of p-synephrine. The acute administration of C. aurantium extract (2.5 % p-synephrine) and p-synephrine produced reduction in locomotor activity, gasping, exophthalmia, piloerection, and salivation, corroborating to the hypothesis that p-synephrine acts not only in p3-adrenoreceptors but also in other adrenergic receptors. However, all the effects were reversible and persisted for 3 h. The adrenergic stimulation alerts for the same possible side effects of p-synephrine and C. aurantium [78]. The subchronic toxicity of Citrus aurantium extract and p-synephrine were also determined and indicated a low subchronic toxicity in mice but a possible alteration in the oxidative metabolism [79]. 

---