Changes in serotonin contents in brain affect metabolic heat production of rabbits in cold

Elevating serotonin (5-HT) contents in brain with 5-hydroxytryptophan (5-HTP) reduced rectal temperature (Tre) in rabbits after peripheral decarboxylase inhibition with the aromatic-L-amino-acid decarboxylase inhibitor R04-4602 at two ambient temperatures (Ta), 2 and 22 degrees C. The hypothermia was brought about by both an increase in respiratory evaporative heat loss (Eres) and a decrease in metabolic rate (MR) in the cold. At a Ta of 22 degrees C, the hypothermia was achieved solely due to an increase in heat loss. Depleting brain contents of 5-HT with intraventricular, 5,7-dihydroxytryptamine (5,7-DHT) produced an increased Eres and ear blood flow even at Ta of 2 degrees C. Also, MR increased at all but the Ta of 32 degrees C. However, depleting the central and peripheral contents of 5-HT with p-chlorophenylalanine (pCPA) produced lower MR accompanied by lower Eres in the cold compared to the untreated control. Both groups of pCPA-treated and 5,7-DHT-treated animals maintained their Tre within normal limits. The data suggest that changes in 5-HT content in brain affects the MR of rabbits in the cold. Elevating brain content of 5-HT tends to depress the MR response to cold, while depleting brain content of 5-HT tends to enhance the MR response to cold.

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Effects of brain monoamine depletion on chlorpromazine-induced hypothermia in rabbits

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y79-002 ◽

1979 ◽

Vol 57 (1) ◽

pp. 16-23 ◽

Cited By ~ 25

Author(s):

M. T. Lin

Keyword(s):

Blood Flow ◽

Heat Production ◽

Intraperitoneal Administration ◽

Induced Hypothermia ◽

Evaporative Heat Loss ◽

Ambient Temperatures ◽

Normal Limits ◽

Wide Range ◽

Monoamine Depletion ◽

6 Hydroxydopamine

The thermal responses of three groups of control, 6-hydroxydopamine (6-OHDA) treated and 5,7-dihydroxytryptamine (5,7-DHT) treated rabbits to the administration of chlorpromazine (CPZ) were assessed at three different ambient temperatures (Ta: 2, 22, and 32 °C). Depleting catecholamines (CA) in brain with 6-OHDA produced a decrease in metabolic rate, in respiratory evaporative heat loss, and in ear blood flow at both Ta's of 2 and 22 °C, while depleting 5-hydroxytryptamine (5-HT) contents in brain with 5,7-DHT produced the opposite responses at the same Ta's. However, these amine-depleted animals maintained their rectal temperatures within normal limits over a wide range of Ta's tested. Furthermore, intraperitoneal administration of CPZ produced hypothermia at both Ta's of 2 and 22 °C. The major cause of the CPZ-induced hypothermia was an inhibition of metabolic heat production at Ta of 2 °C. At Ta of 22 °C, the CPZ-induced hypothermia was due to both a decrease in heat production and an increase in ear blood flow. However, CPZ hypothermia was attenuated in the CA-depleted animals, but was potentiated in the 5-HT-depleted animals. The data indicate that brain monoamines are involved in the central mechanisms of CPZ-induced hypothermia.

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The aromatic amino acid decarboxylase inhibitor, NSD-1015, increases release of dopamine: Response characteristics

Neuropharmacology ◽

10.1016/0028-3908(92)90050-y ◽

1992 ◽

Vol 31 (12) ◽

pp. 1223-1229 ◽

Cited By ~ 8

Author(s):

D. Dluzen ◽

A. Reddy ◽

J. McDermott

Keyword(s):

Amino Acid ◽

Aromatic Amino Acid ◽

Acid Decarboxylase ◽

Decarboxylase Inhibitor ◽

Amino Acid Decarboxylase ◽

Aromatic Amino Acid Decarboxylase ◽

Response Characteristics

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Effects of phentolamine on thermoregulatory functions of rats to different ambient temperatures

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y79-207 ◽

1979 ◽

Vol 57 (12) ◽

pp. 1401-1406 ◽

Cited By ~ 20

Author(s):

M. T. Lin ◽

Andi Chandra ◽

T. C. Fung

Keyword(s):

Heat Loss ◽

Rectal Temperature ◽

Heat Production ◽

Room Temperature ◽

Metabolic Heat Production ◽

Central Component ◽

Evaporative Heat Loss ◽

Central Administration ◽

Ambient Temperatures ◽

Metabolic Heat

The effects of both systemic and central administration of phentolamine on the thermoregulatory functions of conscious rats to various ambient temperatures were assessed. Injection of phentolamine intraperitoneally or into a lateral cerebral ventricle both produced a dose-dependent fall in rectal temperature at room temperature and below it. At a cold environmental temperature (8 °C) the hypothermia in response to phentolamine was due to a decrease in metabolic heat production, but at room temperature (22 °C) the hypothermia was due to cutaneous vasodilatation (as indicated by an increase in foot and tail skin temperatures) and decreased metabolic heat production. There were no changes in respiratory evaporative heat loss. However, in the hot environment (30 °C), phentolamine administration produced no changes in rectal temperature or other thermoregulatory responses. A central component of action is indicated by the fact that a much smaller intraventricular dose of phentolamine was required to exert the same effect as intraperitoneal injection. The data indicate that phentolamine decreases heat production and (or) increases heat loss which leads to hypothermia, probably via central nervous system actions.

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