A pharmacological validation of radiotelemetry in conscious, freely movingrats

Two reference substances were used in the present study. d-Amphetamine is a direct catecholamine-releasing agent which has a marked stimulant effect u pon locomotor activity at low to moderate doses and induces stereotypy at h igher doses. (+/-)8-Hydroxy-2-(di-n-propylamino)-tetraline [(+/-)8-OH-DPAT] is a selective 5-HT1A receptor agonist which produces a well-defined behav ioral syndrome and a dose-dependent hypothermia. The first aim of this stud y was to validate that the d-amphetamine-induced activity monitored by tele metry correlated to that concomitantly measured in automated cages and comp lement these measures with an ethologically based direct observational tech nique, d-Amphetamine (2.5 and 5.0 mu mol/kg s.c.) stimulated locomotion as assessed with radiotelemetry, in automatic cages and by observation. Accomp anying these behavioral effects was a concurrent increase (assessed by radi otelemetry) in heart rate but not in blood pressure. The second part of thi s study examined the pharmacological effects of (+/-)8-OH-DPAT (0.09-6.1 mu mol/kg s.c.) on behavior (observation and activity) and temperature and on the cardiovascular system. (+-)8-OH-DPAT induced the classical serotonergi c syndrome of lower lip retraction, forepaw treading, and flattened body po sture (observation), and this was accompanied by a concomitant hypothermia (radiotelemetry). (+/-)8-OH-DPAT also induced a dose-dependent and signific ant decrease in heart rate for 50 min of the 1-h long observation period. T his was not accompanied by an increase in blood pressure in spite of the in creased activity as seen with all three methods. These results show that ra diotelemetry can be used as a tool to measure activity, core temperature, a nd the cardiovascular parameters in animals that are less stressed than tho se that are restrained for similar more invasive measurements, and that thi s technique can be used in combination with others to produce a more comple te ethogram of the animal's responses to pharmacological challenges. (C) 19 99 Elsevier Science Inc.