Selective labeling of serotonin receptors by d-[3H]lysergic acid diethylamide in calf caudate.
Proceedings of the National Academy of Sciences December 1, 1978 DOI: 10.1073/pnas.75.12.5783 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | In vitro radioligand binding study Peer reviewed |
|---|---|
| Population | Crude homogenates of calf caudate |
| Topics | LSD Serotonin |
| Keywords | Caudate nucleus Animals Cattle Norepinephrine Receptors, dopamine Receptors, serotonin Neurotransmitter agents Binding, competitive Kinetics |
| Key points | Adding phentolamine, apomorphine, and spiperone (50 nM each) to block catecholamine receptors reduced [3H]LSD binding sites in calf caudate homogenates from 1100 to 300 fmol/mg and lowered the serotonin IC50 from 1000 nM to 35 nM, eliminating norepinephrine and dopamine effects. Ergots showed similar IC50 values against [3H]serotonin and [3H]LSD, while tryptamines were more selective against [3H]serotonin; the authors suggest this may indicate two types of serotonin receptors. |
Abstract
Since it was known that d-lysergic acid diethylamide (LSD) affected catecholaminergic as well as serotoninergic neurons, the objective in this study was to enhance the selectivity of [3H]LSD binding to serotonin receptors in vitro by using crude homogenates of calf caudate. In the presence of a combination of 50 nM each of phentolamine (added to preclude the binding of [3H]LSD to alpha-adrenoceptors), apomorphine, and spiperone (added to preclude the binding of [3H]LSD to dopamine receptors), it was found by Scatchard analysis that the total number of [3H]LSD sites went down to 300 fmol/mg, compared to 1100 fmol/mg in the absence of the catecholamine-blocking drugs. The IC50 values (concentrations to inhibit binding by 50%) for various drugs were tested on the binding of [3H]LSD in the presence of 50 nM each of apomorphine (A), phentolamine (P) and spiperone (S). With this combination, the IC50 for serotonin was 35 nM (compared to 1000 nM without it), indicating that [3H]LSD had become considerably more selectively displaceable by serotonin under these conditions whereas the effects of norepinephrine and dopamine on [3H]LSD binding were eliminated. Various ergots had approximately equal IC50 values against [3H]serotonin and [3H]LSD but tryptamines were much more selective against [3H]serotonin; the data may indicate the existence of the two types of serotonin receptors.
Comparable studies
Other preclinical and animal studies on LSD, most cited first.
Citations in the library
Cites 7
- Lysergic Acid Diethylamide: Sensitive Neuronal Units in the Midbrain Raphe Science August 16, 1968
- Evidence for a central 5‐hydroxytryptamine receptor stimulation by lysergic acid diethylamide British Journal of Pharmacology September 1, 1968
- Antagonism of histamine-activated adenylate cyclase in brain by D-lysergic acid diethylamide. Proceedings of the National Academy of Sciences December 1, 1977
- Effects of Hallucinogenic and Tranquilizing Drugs on Serotonin Evoked Uterine Contractions. Experimental Biology and Medicine 1956
- Stereospecific receptor sites for d-lysergic acid diethylamide in rat brain: effects of neurotransmitters, amine antagonists, and other psychotropic drugs. Molecular Pharmacology July 1, 1976
and 2 more in the library