Donitriptan hydrochloride

Donitriptan hydrochloride is a potent, selective, high-efficacy agonist at 5-HT1B/1D receptors both in vivo and in vitro in neuronal and vascular models relevant to migraine.

Donitriptan hydrochloride has subnanomolar affinity for cloned human and nonhuman 5-HT1B and 5-HT1D receptors with Ki values ranging from 0.1-4.3 nM. It potently inhibits forskolin-induced cAMP accumulation mediated by recombinant human and nonhuman, stably transfected 5-HT1B and 5-HT1D receptors with mean EC50 values ranging from 0.2-1.9 nM [1].

In mammals, 5-hydroxytryptamine (5-HT) is important in regulating emotions and related behaviors as a neurotransmitter [2]. In C6 glioma cells transfected with human 5-HT1B or 5-HT1D receptors, donitriptan hydrochloride enhanced specific GTPγ35S binding at both 5-HT1B and 5-HT1D receptors to a greater extent, compared with rizatriptan, naratriptan, sumatriptan, dihydroergotamine and zolmitriptan, but to a level equivalent to which evoked by 5-HT. In guinea pig-isolated trigeminal ganglion neurons, treatment with donitriptan hydrochloride resulted in increase in Ca2+-dependent K+ current (pD2 = 7.3) [1].

Oral administration with donitriptan hydrochloride in guinea pigs resulted in hypothermic responses with an ED50 of 1.6 mg/kg. Compared with zolmitriptan, naratriptan and rizatriptan with an ED50 of 8.3, 9.9 and 12.3 mg/kg, respectively, donitriptan hydrochloride showed superior potency. There is likelihood that donitriptan hydrochloride gains access to the brain [1].Donitriptan hydrochloride is orally active and well tolerated by animals, displays unique craniovascular selectivity and a long duration of action, and gains access to the brain.

References:
[1].  Gareth W. John, Michel Perez, Petrus J. Pauwels, et al. Donitriptan, a Unique High-Efficacy 5-HT1B/1D Agonist: Key Features and Acute Antimigraine Potential. CNS Drug Reviews, 2000, 6(4): 278-289.
[2].  Liang Hua, QinWang, ZhenQin, et al. Detection of 5-hydroxytryptamine (5-HT) in vitro using a hippocampal neuronal network-based biosensor with extracellular potential analysis of neurons. Biosensors and Bioelectronics, 2015, 66:572-578.

Donitriptan, but not sumatriptan, inhibits capsaicin-induced canine external carotid vasodilatation via 5-HT1B rather than 5-HT1D receptors.[Pubmed:16880765]

Br J Pharmacol. 2006 Sep;149(1):82-91.

BACKGROUND AND PURPOSE: It has been suggested that during a migraine attack capsaicin-sensitive trigeminal sensory nerves release calcitonin gene-related peptide (CGRP), resulting in cranial vasodilatation and central nociception; hence, trigeminal inhibition may prevent this vasodilatation and abort migraine headache. This study investigated the effects of the agonists sumatriptan (5-HT(1B/1D) water-soluble), donitriptan (5-HT(1B/1D) lipid-soluble), PNU-142633 (5-HT(1D) water-soluble) and PNU-109291 (5-HT(1D) lipid-soluble) on vasodilator responses to capsaicin, alpha-CGRP and acetylcholine in dog external carotid artery. EXPERIMENTAL APPROACH: 59 vagosympathectomized dogs were anaesthetized with sodium pentobarbitone. Blood pressure and heart rate were recorded with a pressure transducer, connected to a cannula inserted into a femoral artery. A precalibrated flow probe was placed around the common carotid artery, with ligation of the internal carotid and occipital branches, and connected to an ultrasonic flowmeter. The thyroid artery was cannulated for infusion of agonists. KEY RESULTS: Intracarotid infusions of capsaicin, alpha-CGRP and acetylcholine dose-dependently increased blood flow through the carotid artery. These responses remained unaffected after intravenous (i.v.) infusions of sumatriptan, PNU-142633, PNU-109291 or physiological saline; in contrast, donitriptan significantly attenuated the vasodilator responses to capsaicin, but not those to alpha-CGRP or acetylcholine. Only sumatriptan and donitriptan dose-dependently decreased the carotid blood flow. Interestingly, i.v. administration of the antagonist, SB224289 (5-HT(1B)), but not of BRL15572 (5-HT(1D)), abolished the inhibition by donitriptan. CONCLUSIONS AND IMPLICATIONS: Our results suggest that the inhibition produced by donitriptan of capsaicin-induced external carotid vasodilatation is mainly mediated by 5-HT(1B), rather than 5-HT(1D), receptors, probably by a central mechanism.

Donitriptan decreases jugular venous oxygen saturation in rats in the absence of cranial vasoconstriction: an overlooked mechanism of antimigraine action?[Pubmed:16027226]

J Pharmacol Exp Ther. 2005 Nov;315(2):849-57.

The aim of the present study was to determine whether donitriptan and sumatriptan decreased jugular venous oxygen saturation and increased carbon dioxide partial pressure in venous blood. However, previous studies conducted with these compounds cannot discriminate whether the decrease of venous oxygen saturation is dependent of cranial vasoconstrictor. In the present study, vehicle (n = 10), donitriptan (2.5, 10, and 40 microg/kg; n = 8) or sumatriptan (630 microg/kg; n = 8) were infused into the carotid artery in the anesthetized rat. Regional blood flows were evaluated in the presence of donitriptan (10 microg/kg; n = 6) or vehicle (n = 6). Jugular venous oxygen saturation was significantly decreased by donitriptan (from 10 microg/kg) with maximal changes of -32.9 +/- 8.0%. Jugular carbon dioxide partial pressure was increased by donitriptan, reaching maximal changes of 17.7 +/- 4.6% (P < 0.05 versus vehicle). Similarly, sumatriptan significantly decreased venous oxygen saturation and increased jugular carbon dioxide partial pressure. These changes induced by donitriptan are abolished by the 5-hydroxytryptamine (5-HT)(1B/1D) receptor antagonist GR 127935 (N-[4-methoxy-3-(4-methyl-1-piperazinyl)phenyl]-2-[-methyl-4(5-methyl-1,2,4)-oxad iazol-3-yl]-(1,1 biphenyl)-4-carboxamide dihydrochloride). In addition, donitriptan was devoid of significant effects on systemic arterial pressure, heart rate, or regional blood flows, including systemic arterial-jugular venous anastomotic, systemic, or cranial. The results demonstrate that donitriptan increases cerebral oxygen consumption by 5-HT(1B/1D) receptor activation in the absence of cranial vasoconstriction.

Donitriptan selectively decreases jugular venous oxygen saturation in the anesthetized pig: further insights into its mechanism of action relevant to headache relief.[Pubmed:12606602]

J Pharmacol Exp Ther. 2003 May;305(2):749-54.

The effects of donitriptan on systemic arterial-jugular venous oxygen saturation difference were evaluated in pentobarbitone-anesthetized pigs. Oxygen and carbon dioxide partial pressures in systemic arterial and jugular venous blood as well as hemoglobin oxygen saturation were determined by conventional blood gas analysis. Vehicle (40% polyethyleneglycol in saline, n = 9) or donitriptan (0.01, 0.04, 0.16, 0.63, 2.5, 10, and 40 microg/kg, n = 7) were cumulatively infused over 15 min/dose. The involvement of 5-hydroxytryptamine(1B) (5-HT(1B)) receptors was assessed in the presence of the 5-HT(1B/1D) receptor antagonist, GR 127935. Donitriptan decreased markedly and dose dependently jugular venous oxygen saturation [ED(50) 0.5 (0.3-1.1) microg/kg], in parallel with increases in carotid vascular resistance [ED(50) 0.9 (0.7-1.1) microg/kg]. Since arterial oxygen saturation and partial pressure remained unchanged, donitriptan significantly increased arteriovenous oxygen saturation difference from 0.63 microg/kg (maximal variation: 57 +/- 18%, P < 0.05 compared with vehicle). Unexpectedly, donitriptan from 2.5 microg/kg induced marked and significant increases in carbon dioxide partial pressure (pVCO(2)) in venous blood (maximal increase 18.8 +/- 5.7%; P < 0.05 compared with vehicle). Pretreatment with GR 127935 (0.63 mg/kg, n = 5) abolished the fall in venous oxygen saturation and the increase in carotid vascular resistance and reduced the increases in pVCO(2) induced by donitriptan. The results demonstrate that donitriptan, via 5-HT(1B) receptor activation, decreases the oxygen saturation of venous blood draining the head, concomitantly with cranial vasoconstriction. Since donitriptan also increased pVCO(2), an effect upon cerebral oxygen consumption and metabolism is suggested in addition to cranial vasoconstriction, which may be relevant to its headache-relieving effects.