Involvement of serotoninergic receptors in the anteroventral preoptic region on hypoxia-induced hypothermia.
Hypoxia causes a regulated decrease in body temperature (Tb). There is circumstantial evidence that the neurotransmitter serotonin (5-HT) in the anteroventral preoptic region (AVPO) mediates this response. However, which 5-HT receptor(s) is (are) involved in this response has not been assessed. Thus, we investigated the participation of the 5-HT receptors (5-HT1, 5-HT2, and 5-HT7) in the AVPO in hypoxic hypothermia. To this end, Tb of conscious Wistar rats was monitored by biotelemetry before and after intra-AVPO microinjection of methysergide (a 5-HT1 and 5-HT2 receptor antagonist, 0.2 and 2 microg/100 nL), WAY-100635 (a 5-HT(1A) receptor antagonist, 0.3 and 3 microg/100 nL), and SB-269970 (a 5-HT7 receptor antagonist, 0.4 and 4 micro/100 nL), followed by 60 min of hypoxia exposure (7% O2). During the experiments, the mean chamber temperature was 24.6 +/- 0.7 degrees C (mean +/- SE) and the mean room temperature was 23.5 +/- 0.8 degrees C (mean +/- SE). Intra-AVPO microinjection of vehicle or 5-HT antagonists did not change Tb during normoxic conditions. Exposure of rats to 7% of inspired oxygen evoked typical hypoxia-induced hypothermia after vehicle microinjection, which was not affected by both doses of methysergide. However, WAY-100635 and SB-269970 treatment attenuated the drop in Tb in response to hypoxia. The effect was more pronounced with the 5-HT7 antagonist since both doses (0.4 and 4 microg/0.1 microL) were capable of attenuating the hypothermic response. As to the 5-HT(1A) antagonist, the attenuation of hypoxia-induced hypothermia was only observed at the higher dose. Therefore, the present results are consistent with the notion that 5-HT acts on both 5-HT(1A) and 5-HT7 receptors in the AVPO to induce hypothermia, during hypoxia.
Gargaglioni
Luciane H
LH
Department of Animal Morphology and Physiology, State University of Sao Paulo-FCAV at Jaboticabal, SP, Brazil. lucihel@fcav.unesp.br
Steiner
Alexandre A
AA
Branco
Luiz G S
LG
D000818:Animals; D001831:Body Temperature / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D007035:Hypothermia / Q000209:etiology / Q000378:metabolism*; D000860:Hypoxia / Q000150:complications; D008297:Male; D008845:Microinjections / Q000379:methods; D015999:Multivariate Analysis; D011301:Preoptic Area / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D011985:Receptors, Serotonin / Q000145:classification / Q000502:physiology*; D012702:Serotonin Antagonists / Q000494:pharmacology
D011985:Receptors, Serotonin; D012702:Serotonin Antagonists