Effects of central application of naloxone on the skin temperature response in morphine-dependent rats.
This study was designed to identify if the surge in tail skin temperature (TST) observed following systemic administration of naloxone to morphine-dependent rats is mediated by a specific brain locus. Female rats were fitted with cannula located either in the preoptic area-anterior hypothalamus, locus coeruleus, or the frontal cortex. TST was monitored every 5 min for 60 min following central administration of naloxone (1-40 micrograms/0.4 microliters), in morphine-dependent rats. Regardless of the central site of naloxone injection, TST was significantly increased 4-5 degrees C. A threshold dose of 20 micrograms/0.4 microliters (10 micrograms/0.2 microliters, bilaterally) of naloxone was identified to produce this surge in TST in all three brain regions. These results suggest that morphine dependency sensitizes several brain regions to administration of naloxone such that the narcotic antagonist produces a similar change in TST as is observed following its systemic administration. These data further support the use of our morphine-dependent rat model to study the central mechanisms of the menopausal hot flush, and provide additional evidence that the flush response is centrally mediated.
D000818:Animals; D007025:Anterior Hypothalamic Nucleus / Q000187:drug effects; D001921:Brain / Q000187:drug effects* / Q000503:physiopathology; D004305:Dose-Response Relationship, Drug; D005260:Female; D005625:Frontal Lobe / Q000187:drug effects; D008125:Locus Coeruleus / Q000187:drug effects; D009021:Morphine Dependence / Q000503:physiopathology*; D009270:Naloxone / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D012881:Skin Temperature / Q000187:drug effects*; D013997:Time Factors
D009270:Naloxone