Thursday, December 22, 2005

Specific CYP displacement of 3HDPAT

1 ug/ml of CYP ( 2.85 micromolar ) displaces 83% of 3HDPAT, a 5HT1a ligand. 0.36 ug/ml CYP ( 1.03 micromolar ) displaces 40% of 3HDPAT.

3-0H CYP is somewhat better as a displacing drug (ligand) with total displacement of 3HDPAT by 1 ug/ml 3-OH CYP and 52% displacement by 0.36 ug/ml. This would make the concentration necessary for 50% displacement of the ligand, by 3-OH cyproheptadine, ~ 1.03 micromolar, assuming a molecuar weight of 3-OH cyproheptadine of 303 this, the IC50, would be 1.2 micromolar. See data, which is preliminary, below.

The IC50 for cyproheptadine relative to 3H-8-OH-DPAT was, in -log IC 50, M, 6.01, cf. Josee E. Leysen in Neurophamacology of Serotonin, p. 86. In this book, p. 302, is also reported "Cyproheptadine and methysergide inhibit the firing of raphe neurons when applied locally (Haigler and Aghajanian 1974)." This is consistent with a locus coeruleus action posited in my 1991 case reports re: nightmares.


A. Richard Green (ed), Neuropharmacology of Serotonin, Oxford University Press, 1985

In Green, for IC50, cited:
Gozlan,H, et al., Hamon, M (1983), Identification of presynaptic autoreceptors using a new ligand: 3H-PAT. Nature 305, 140; Leysen JE (1981) Serotonergic receptors in brain tissue: Properties and idientification of various [3H]ligand binding sites in vitro. J. Physiol. 77, 351

Haigler, HJ, and Aghajanian, GK (1974) J. Neural. Transm., 35, 257.

re HT1a agonist effects and reversal:
Trickelbank, MD (1984a) Behavioural effects of 8-hydroxy-2-(di-n-propylamine) tetralin, Br. J. Pharmac. 81, 26P, see also 140P.
Oberlander L cited in Green p 363 also has contributions.


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