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Adrenergic Agonists: Mixed-Action Agents

Adrenergic Agonists: Mixed-Action Agents

Mixed-action adrenergic agonists, like ephedrine and pseudoephedrine, directly and indirectly affect adrenergic receptors. These agents stimulate adrenoceptors and indirectly release stored neurotransmitters, amplifying the adrenergic response.
Ephedrine and pseudoephedrine lack a catecholamine group, making them less susceptible to degradation by metabolic enzymes. They have increased oral bioavailability and lipophilicity, resulting in a longer duration of action. Their response is reduced by...

Adrenergic Agonists: Chemistry and Structure-Activity Relationship

Adrenergic Agonists: Chemistry and Structure-Activity Relationship

Adrenergic agonists' structure-activity relationship (SAR) determines their selectivity and efficacy. These agonists comprise a phenylethylamine moiety with an aromatic ring and an ethylamine side chain.
Aromatic ring substitutions: Substituting the aromatic ring with –OH groups at positions 3 and 4 yields catecholamines (e.g., epinephrine), which have a high affinity for adrenoceptors. Hydrogen bonding between –OH groups and receptors enhances adrenergic activity.
Separation of the aromatic...

Sympathetic Activation

Sympathetic Activation

The sympathetic division can influence tissues and organs by releasing norepinephrine at peripheral synapses and distributing epinephrine and norepinephrine through the bloodstream. In times of crisis or stress, sympathetic activation occurs, which is regulated by sympathetic centers in the hypothalamus. As a result, sympathetic activation prepares the body for physical exertion, rapid ATP production, and heightened alertness, allowing individuals to respond effectively to challenging or...

Adrenergic Agonists: Direct-Acting Agents

Adrenergic Agonists: Direct-Acting Agents

Drugs that mimic the action of endogenous catecholamines like noradrenaline and adrenaline are called adrenergic agonists or sympathomimetics. Based on their mechanism of action, sympathomimetics can be classified as direct-, indirect-, or mixed-acting sympathomimetics. Direct-acting adrenergic agonists activate adrenoceptors without affecting presynaptic neurons, making them independent of neuronal catecholamine-depleting agents like reserpine and guanethidine.
These agents can be classified...

Antiarrhythmic Drugs: Class II Agents as β-Adrenergic Blockers

Antiarrhythmic Drugs: Class II Agents as β-Adrenergic Blockers

Adrenergic stimulation generally impacts cardiac rate and rhythm. Specifically, stimulation of the β-adrenoceptors triggers an increase in intracellular calcium ion influx and pacemaker currents, which may cause arrhythmias. Catecholamines like adrenaline also demonstrate β2-adrenoceptor-mediated hypokalemia, impacting cardiac action potential and disrupting the normal cardiac rhythm. Class II antiarrhythmic drugs are β-adrenoceptor antagonists or β-blockers, which indirectly block calcium...

Drugs Affecting Neurotransmitter Release or Uptake

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Certain drugs can affect how neurotransmitters called catecholamines, are released or taken back up in the adrenergic neuron. They can have different effects on the body's sympathetic transmission. Reserpine, a natural compound found in the Rauwolfia shrub, blocks a transporter called vesicular monoamine transporter (VMAT), which leads to a buildup of catecholamines in the cell and reduces sympathetic transmission. Another drug called guanethidine works in multiple ways, including blocking...

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Related Experiment Video

Updated: Jul 5, 2026

Contractions of Human-iPSC-derived Cardiomyocyte Syncytia Measured with a Ca-sensitive Fluorescent Dye in Temperature-controlled 384-well Plates

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Published on: October 18, 2018

[Chronotropic activity of semax].

E B Arushanian, A V Popov

Eksperimental'Naia I Klinicheskaia Farmakologiia

|May 21, 2008

Summary

This summary is machine-generated.

The nootropic drug Semax normalized circadian rhythms in rats, improving locomotor activity and reducing biological timekeeping irregularities. This suggests Semax may enhance cognitive function by synchronizing biological rhythms.

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Preparation of Human Myocardial Tissue for Long-Term Cultivation

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Contractions of Human-iPSC-derived Cardiomyocyte Syncytia Measured with a Ca-sensitive Fluorescent Dye in Temperature-controlled 384-well Plates

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Published on: October 18, 2018

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Area of Science:

Neuroscience
Chronobiology
Pharmacology

Context:

Circadian rhythms regulate numerous physiological processes, and their disruption is linked to cognitive impairment.
Nootropic drugs are being investigated for their potential to enhance cognitive function.
Semax, a peptide analog of ACTH (4-10), is a known nootropic agent.

Purpose:

To investigate the effects of chronic Semax administration on circadian locomotor rhythms in a rat model.
To determine if Semax exhibits chronobiological effects beyond its known cognitive-enhancing properties.

Summary:

Chronic administration of Semax led to the normalization of circadian locomotor rhythm in rats.
Specific effects observed included increased rhythm amplitude, acrophase shift, and altered spectral characteristics.
Semax also reduced the integral chronobiological index, indicating a more consolidated rhythm.

Impact:

The findings suggest that Semax possesses rhythm-synchronizing chronotropic activity.
This chronotropic activity may contribute to the specific cognitive-enhancing effects of Semax.
This study highlights a potential novel mechanism of action for nootropic drugs in regulating biological rhythms.