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Silenieks LB, Carroll NK, Van Niekerk A, Van Niekerk E, Taylor C, Upton N, Higgins GA. Evaluation of Selective 5-HT 2C Agonists in Acute Seizure Models. ACS Chem Neurosci 2019; 10:3284-3295. [PMID: 31082204 DOI: 10.1021/acschemneuro.8b00739] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The 5-HT releaser/reuptake inhibitor fenfluramine has been recently reported to provide benefit as an adjunctive treatment for Dravet and Lennox-Gastaut syndromes, two types of severe childhood epilepsy. Despite its enhancement of 5-HT function, many effects of fenfluramine have been demonstrated to be dependent on 5-HT2C receptor activation, suggesting that 5-HT2C receptor activation may have an anticonvulsant property. The present study was designed to evaluate fenfluramine and 5-HT agonists of varying 5-HT2C agonist selectivity, the relatively nonselective mCPP and Ro 60-0175, and the selective 5-HT2C agonists lorcaserin and CP-809101 across a variety of acute seizure tests conducted in adult rats and mice, which have been instrumental in identifying the majority of clinically efficacious antiepileptic drugs. Tests included the maximal electroshock seizure (MES), MES threshold, and 6 Hz electrical convulsive seizure models and the chemoconvulsant pentylenetetrazole test. The effect of mCPP, lorcaserin, and CP-809101 against electrically evoked seizures in amygdala kindled rats was also investigated. Overall, at doses known to interact with 5-HT2CR, there was no clear class-related effect of these agonists in any test. The only notable antiseizure effect of fenfluramine was inhibition of MES-induced tonic seizures in the rat. The current preclinical studies using the classical acute seizure tests and an amygdala kindling model do not identify a reliable antiseizure effect of fenfluramine, an agent now used in the treatment of human epilepsies, including Dravet syndrome and Lennox-Gastaut syndrome. Given the nature of these epilepsies, early life and/or genetic models may have better construct validity and be more appropriate for further study.
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Affiliation(s)
- Leonardo B. Silenieks
- Intervivo Solutions Inc, Toronto, ON M5A 4K2, Canada
- Vivocore, Toronto, ON N1M 2W4, Canada
| | | | | | | | | | - Neil Upton
- Transpharmation Ltd, London NW10NH, United Kingdom
| | - Guy A. Higgins
- Intervivo Solutions Inc, Toronto, ON M5A 4K2, Canada
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON ON M5S, Canada
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Higgins GA, Silenieks LB, Patrick A, De Lannoy IAM, Fletcher PJ, Parker LA, MacLusky NJ, Sullivan LC, Chavera TA, Berg KA. Studies To Examine Potential Tolerability Differences between the 5-HT 2C Receptor Selective Agonists Lorcaserin and CP-809101. ACS Chem Neurosci 2017; 8:1074-1084. [PMID: 28338324 DOI: 10.1021/acschemneuro.6b00444] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Lorcaserin (LOR) is a selective 5-HT2C receptor agonist that has been FDA approved as a treatment for obesity. The most frequently reported side-effects of LOR include nausea and headache, which can be dose limiting. We have previously reported that in the rat, while LOR produced unconditioned signs characteristic of nausea/malaise, the highly selective 5-HT2C agonist CP-809101 (CP) produced fewer equivalent signs. Because this may indicate a subclass of 5-HT2C agonists having better tolerability, the present studies were designed to further investigate this apparent difference. In a conditioned gaping model, a rodent test of nausea, LOR produced significantly higher gapes compared to CP consistent with it having higher emetogenic properties. Subsequent studies were designed to identify features of each drug that may account for such differences. In rats trained to discriminate CP-809101 from saline, both CP and LOR produced full generalization suggesting a similar interoceptive cue. In vitro tests of functional selectivity designed to examine signaling pathways activated by both drugs in CHO (Chinese hamster ovary) cells expressing h5-HT2C receptors failed to identify evidence for biased signaling differences between LOR and CP. Thus, both drugs showed similar profiles across PLC, PLA2, and ERK signaling pathways. In studies designed to examine pharmacokinetic differences between LOR and CP, while drug plasma levels correlated with increasing dose, CSF levels did not. CSF levels of LOR increased proportionally with dose; however CSF levels of CP plateaued from 6 to 12 mg/kg. Thus, the apparently improved tolerability of CP likely reflects a limit to CNS levels attained at relatively high doses.
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Affiliation(s)
- Guy A. Higgins
- InterVivo Solutions Inc., 120 Carlton Street, Toronto, Ontario M5A 4K2, Canada
- Department of Pharmacology & Toxicology, University of Toronto, 1 King’s College Circle, Toronto, Ontario M5S 1A8, Canada
| | | | - Amy Patrick
- InterVivo Solutions Inc., 120 Carlton Street, Toronto, Ontario M5A 4K2, Canada
| | | | - Paul J. Fletcher
- Centre for Addiction and Mental Health, 250
College St, Toronto, Ontario M5T 1L8, Canada
- Department of Psychology & Psychiatry, University of Toronto, 100 St. George Street, Toronto, Ontario M5S 3G3, Canada
| | - Linda A. Parker
- Department
of Psychology, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada
| | - Neil J. MacLusky
- Ontario Veterinary College, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada
| | - Laura C. Sullivan
- Department of Pharmacology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, Texas 78229, United States
| | - Teresa A. Chavera
- Department of Pharmacology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, Texas 78229, United States
| | - Kelly A. Berg
- Department of Pharmacology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, Texas 78229, United States
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Higgins GA, Silenieks LB, Altherr EB, MacMillan C, Fletcher PJ, Pratt WE. Lorcaserin and CP-809101 reduce motor impulsivity and reinstatement of food seeking behavior in male rats: Implications for understanding the anti-obesity property of 5-HT2C receptor agonists. Psychopharmacology (Berl) 2016; 233:2841-56. [PMID: 27241709 DOI: 10.1007/s00213-016-4329-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Accepted: 05/09/2016] [Indexed: 12/28/2022]
Abstract
RATIONALE The 5-HT2C receptor agonist lorcaserin (Belviq®) has been approved by the FDA for the treatment of obesity. Impulsivity is a contributory feature of some eating disorders. OBJECTIVE Experiments investigated the effect of lorcaserin and the highly selective 5-HT2C agonist CP-809101 on measures of impulsivity and on reinstatement of food-seeking behaviour, a model of dietary relapse. The effect of both drugs on 22-h deprivation-induced feeding was also examined, as was the effect of prefeeding in each impulsivity test. RESULTS Lorcaserin (0.3-0.6 mg/kg SC) and CP-809101 (0.6-1 mg/kg SC) reduced premature responding in rats trained on the 5-CSRTT and improved accuracy in a Go-NoGo task by reducing false alarms. At equivalent doses, both drugs also reduced reinstatement for food-seeking behaviour. Neither drug altered impulsive choice measured in a delay-discounting task. Lorcaserin (1-3 mg/kg SC) and CP-809101 (3-6 mg/kg SC) reduced deprivation-induced feeding but only at higher doses. CONCLUSIONS These results suggest that in addition to previously reported effects on satiety and reward, altered impulse control may represent a contributory factor to the anti-obesity property of 5-HT2C receptor agonists. Lorcaserin may promote weight loss by improving adherence to dietary regimens in individuals otherwise prone to relapse and may be beneficial in cases where obesity is associated with eating disorders tied to impulsive traits, such as binge eating disorder.
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Affiliation(s)
- Guy A Higgins
- InterVivo Solutions Inc., 120 Carlton Street, Toronto, ON, M5A 4K2, Canada. .,Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON, M5S 4K2, Canada.
| | - Leo B Silenieks
- InterVivo Solutions Inc., 120 Carlton Street, Toronto, ON, M5A 4K2, Canada
| | - Everett B Altherr
- Department of Psychology, Wake Forest University, Winston-Salem, NC, 27109, USA
| | - Cam MacMillan
- Vivocore, 120 Carlton Street, Toronto, ON, M5A 4K2, Canada
| | - Paul J Fletcher
- Department of Psychiatry, University of Toronto, Toronto, ON, M5T 1R8, Canada.,Department of Psychology, University of Toronto, Toronto, ON, M5S 3G3, Canada.,Centre for Addiction and Mental Health, 250 College Street, Toronto, ON, M5T 1R8, Canada
| | - Wayne E Pratt
- Department of Psychology, Wake Forest University, Winston-Salem, NC, 27109, USA
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