Phenylephrine is a powerful vasoconstrictor. It is used as a nasal decongestant and cardiotonic agent. Phenylephrine is a postsynaptic α1-receptor agonist with little effect on β-receptors of the heart. Parenteral administration of phenylephrine causes a rise in systolic and diastolic pressures, a slight decrease in cardiac output, and a considerable increase in peripheral resistance; most vascular beds are constricted, and renal, splanchnic, cutaneous, and limb blood flows are reduced while coronary blood flow is increased. Phenelephrine also causes pulmonary vessel constriction and subsequent increase in pulmonary arterial pressure. Vasoconstriction in the mucosa of the respiratory tract leads to decreased edema and increased drainage of sinus cavities. In general, α1-adrenergic receptors mediate contraction and hypertrophic growth of smooth muscle cells. α1-receptors are 7-transmembrane domain receptors coupled to G proteins, Gq/11. Three α1-receptor subtypes, which share approximately 75% homology in their transmembrane domains, have been identified: α1A (chromosome 8), α1B (chromosome 5), and α1D (chromosome 20). Phenylephrine appears to act similarly on all three receptor subtypes. All three receptor subtypes appear to be involved in maintaining vascular tone. The α1A-receptor maintains basal vascular tone while the α1B-receptor mediates the vasocontrictory effects of exogenous α1-agonists. Activation of the α1-receptor activates Gq-proteins, which results in intracellular stimulation of phospholipases C, A2, and D. This results in mobilization of Ca2+ from intracellular stores, activation of mitogen-activated kinase and PI3 kinase pathways and subsequent vasoconstriction. Phenylephrine produces its local and systemic actions by acting on α1-adrenergic receptors peripheral vascular smooth muscle. Stimulation of the α1-adrenergic receptors results in contraction arteriolar smooth muscle in the periphery. Phenylephrine decreases nasal congestion by acting on α1-adrenergic receptors in the arterioles of the nasal mucosa to produce constriction; this leads to decreased edema and increased drainage of the sinus cavities. Phenylephrine is mainly used to treat nasal congestion, but may also be useful in treating hypotension and shock, hypotension during spinal anaesthesia, prolongation of spinal anaesthesia, paroxysmal supraventricular tachycardia, symptomatic relief of external or internal hemorrhoids, and to increase blood pressure as an aid in the diagnosis of heart murmurs.

alpha-yohmbine (aka rauwloscine) is a diastereomer of yohimbine and shares many of the same properties. Rauwolscine acts as an alpha-2-adrenergic antagonist and is therefore used as an unregulated nutritional supplement for fat-burning and CNS stimulation. Rauwolscine is also an antagonist of the HT2B receptor and has been investigated for the potential to mitigate blood vessel spasms.

PNU-282987 is a potent and selective a7 nAChR agonist. This compound showed high affinity for the rat a7 nAChR (Ki = 26 nM) and activity at the a7–5-HT3 chimera (EC50 = 128 nM). In addition, PNU-282987 was found to be inactive at all tested monoamine, muscarine, glutamate, and GABA receptors at 1 uM concentration, except 5-HT3 receptors (Ki = 930 nM). The highly selective and potent a7 nAChR agonist PNU-282987 enhances GABAergic synaptic activity in the hippocampus in vitro, and reverses amphetamine induced auditory gating deficit in anesthetized rats. In addition, PNU-282987 improves the inherent gating deficit observed in a subset of rats and enhances amphetamine induced hippocampal activity. These results support the concept that a7 nAChR agonists represent a novel, potential pharmacotherapy in treatment of schizophrenia. It also has being shown that acute lung injury is reduced by PNU-282987 through changes in the macrophage profile.

A-582941 was found to exhibit high-affinity binding and agonism at alpha-7 nicotinic acetylcholine receptor (α7-nAChR), with acceptable pharmacokinetic properties and excellent distribution to the central nervous system. In vitro and in vivo studies indicated that A-582941 activates signaling pathways known to be involved in cognitive function such as ERK1/2 and CREB phosphorylation. A-582941 enhanced cognitive performance in behavioral assays including the monkey delayed matching-to-sample, rat social recognition, and mouse inhibitory avoidance models that capture domains of working memory, short-term recognition memory, and long-term memory consolidation, respectively. AbbVie is developing α7-nAChR agonists including A-582941 as neuroprotective agents for the treatment of cognitive disorders such as Alzheimer's disease and schizophrenia. Development is at the preclinical stage.

Indoramin is an alpha-1 selective antagonist of adrenergic receptor, sold under trade names Baratol and Doralese, and now available as a generic. It has no reflex tachycardia and direct myocardial depression action and is used to treat benign prostate hyperplasia (as 20 mg tablets) or reduce blood pressure (as 25 mg strength tablets). It was also investigated as a treatment of a migraine and congestive heart failure.

Mianserin is a tetracyclic antidepressant used for the treatment of depression. It was investigated as an adjuvant for reduction of negative and cognitive symptoms of schizophrenia, as an aid for opioid detoxification therapy (where it reduced symptoms but lead to higher drop-out rate), and for the treatment of post-traumatic stress disorder (where it was ineffective). Mianserin has a broad spectrum of activity with the most potent binding to 5-HT2A, 5-HT2C, H1, alpha2A and alpha2C receptor.