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Effects of 3,4-methylenedioxymethamphetamine on autonomic thermoregulatory responses of the rat
C J Gordon1, W P Watkinson, J P O'Callaghan
1Neurotoxicology Division, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711.
Abstract:
3,4-Methylenedioxymethamphetamine (MDMA), a substituted amphetamine analogue which stimulates serotonin release in the CNS, has been shown to induce near lethal elevations in core temperature in the rat. To characterize the effects of MDMA on temperature regulation, we measured metabolic rate (MR), evaporative water loss (EWL), motor activity (MA), and colonic temperature (Tc) in male, Long-Evans rats at 60 min following 30 mg/kg (SC) MDMA or saline at ambient temperature (Ta) of 10, 20 and 30 degrees C. MDMA caused an elevation in MR at Ta's of 20 and 30 degrees C but had no effect at 10 degrees C. At a Ta of 30 degrees C, MR of the MDMA group was double that of the saline group. EWL was elevated by MDMA, an effect which was potentiated with increasing Ta. MDMA also elicited an increase in MA at all three Ta's. MDMA led to a 3.2 degrees C increase in Tc at 30 degrees C, no change in Tc at 20 degrees C, and a 2.0 degrees C decrease in Tc at 10 degrees C. A second study found that treatment with 20 mg/kg MDMA failed to elicit an increase in blood flow to the tail in spite of a hyperthermic core temperature of 41.4 degrees C. Preliminary studies using radiotelemetry methodology suggested that MDMA lethality is preceded by precipitous elevations in heart rate and core temperature. The data suggest that, at relatively warm Ta's. MDMA-induced stimulation of serotonergic pathways causes an elevation in MR and peripheral vasoconstriction, thus producing life-threatening elevations in Tc.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
3,4-Methylenedioxymethamphetamine (MDMA) significantly impacts rat thermoregulation, increasing metabolic rate and motor activity, especially at warmer temperatures. This leads to potentially lethal core temperature elevations, suggesting peripheral vasoconstriction is involved.
Area of Science:
- Pharmacology
- Physiology
- Neuroscience
Background:
- 3,4-Methylenedioxymethamphetamine (MDMA) is known to stimulate serotonin release in the central nervous system (CNS).
- MDMA has been observed to induce potentially lethal increases in core body temperature in rats.
Purpose of the Study:
- To investigate the specific effects of MDMA on thermoregulation in rats.
- To characterize the impact of MDMA on metabolic rate, evaporative water loss, motor activity, and core body temperature across different ambient temperatures.
Main Methods:
- Male Long-Evans rats were administered MDMA (30 mg/kg, SC) or saline.
- Measurements of metabolic rate (MR), evaporative water loss (EWL), motor activity (MA), and colonic temperature (Tc) were taken at ambient temperatures (Ta) of 10, 20, and 30°C.
- A secondary study assessed tail blood flow, and preliminary radiotelemetry data on heart rate and Tc were collected.
Main Results:
- MDMA elevated MR at 20°C and 30°C Ta, but not at 10°C Ta.
- EWL increased with MDMA, potentiated by higher Ta, and MA increased at all tested Ta.
- MDMA caused a 3.2°C increase in Tc at 30°C Ta, no change at 20°C Ta, and a 2.0°C decrease at 10°C Ta.
- MDMA-induced hyperthermia (41.4°C Tc) did not increase tail blood flow.
Conclusions:
- MDMA-induced serotonergic stimulation elevates MR and causes peripheral vasoconstriction at warmer ambient temperatures.
- These physiological changes contribute to life-threatening increases in core body temperature.
- MDMA's effects on thermoregulation are temperature-dependent and involve complex cardiovascular and metabolic adjustments.