3,4-Methylenedioxymethamphetamine- and 8-hydroxy-2-di-n-propylamino-tetralin-induced hypothermia: role and location of 5-hydroxytryptamine 1A receptors.

Abstract

The popular drug of abuse 3,4-methylenedioxymethamphetamine (MDMA) has complex interactions with thermoregulatory systems, resulting in either hyperthermia or hypothermia. MDMA induces hypothermia when given to animals housed at a low ambient temperature. In this study we report that MDMA (7.5 mg/kg i.p.) given at normal ambient temperatures of 24 to 25 degrees C caused, in conscious freely moving rats, hypothermia (mean decrease from baseline of 1.1 +/- 0.06 degrees C at 40 min). Pretreating animals with a 0.5 mg/kg i.p. dose of the 5-hydroxytryptamine 1A (5-HT(1A)) antagonist N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-2-pyridinylcyclohexanecarboxamide (WAY 100635) not only prevented MDMA-induced hypothermia, but resulted in the development of hyperthermia (mean temperature increase from baseline of 0.74 +/- 0.2 degrees C at 120 min). After treatment with WAY 100635, MDMA also elicited an enhanced tachycardia (mean increases in heart rate from baseline of 110 +/- 16 beats/min at 90 min). To identify the location of 5-HT(1A) receptors responsible for hypothermia induced by MDMA, we first investigated the role of 5-HT(1A) receptors in the rostral raphe pallidus (rRP) in decreases in temperature evoked by the known 5-HT(1A) agonist 8-hydroxy-2-di-n-propylamino-tetralin (DPAT). Microinjections of 0.5 nmol of WAY 100635 into the rRP significantly attenuated DPAT (0.2 mg/kg i.p.)-elicited hypothermia. In parallel experiments, we found that microinjections of WAY 100635 into the rRP, while significantly augmenting MDMA-mediated tachycardia, did not alter body temperature. These results demonstrate that although hypothermia mediated by both MDMA and DPAT shares a common dependence on the activation of 5-HT(1A) receptors, the location of these receptors is different for each drug.

• Authors: Daniel E Rusyniak, Maria V Zaretskaia, Dmitry V Zaretsky, Joseph A DiMicco
• Journal: The Journal of pharmacology and experimental therapeutics (J Pharmacol Exp Ther) Vol. 323 Issue 2 Pg. 477-87 (Nov 2007) ISSN: 0022-3565 [Print] United States
• PMID: 17702902 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• Piperazines
• Pyridines
• Receptor, Serotonin, 5-HT1A
• N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridinyl)cyclohexanecarboxamide
• 8-Hydroxy-2-(di-n-propylamino)tetralin
• N-Methyl-3,4-methylenedioxyamphetamine

Topics

• 8-Hydroxy-2-(di-n-propylamino)tetralin (analysis, pharmacology)
• Animals
• Blood Pressure (drug effects)
• Body Temperature (drug effects)
• Dose-Response Relationship, Drug
• Heart Rate (drug effects)
• Male
• Motor Activity (drug effects)
• N-Methyl-3,4-methylenedioxyamphetamine (pharmacology)
• Piperazines (pharmacology)
• Pyridines (pharmacology)
• Raphe Nuclei (drug effects, physiology)
• Rats
• Rats, Sprague-Dawley
• Receptor, Serotonin, 5-HT1A (physiology)