Hypothermic Effects of Dopamine D 3 Receptor Agonists in the Island of Calleja Magna. Potentiation by D 1 Activation

• Published in: Pharmacology, biochemistry and behavior Vol. 60; no. 2; pp. 313 - 319
• Main Authors: Barik, Samir, De Beaurepaire, Renaud
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01-06-1998
• Subjects: 7-OH-DPAT; Hypothermia; Locomotor activity; Microinjection; Nucleus accumbens; Quinelorane; Quinpirole; SKF 38393; Nucleus accumbens; Quinpirole; 7-OH-DPAT; Microinjection; SKF 38393; Quinelorane; Locomotor activity; Hypothermia
• ISSN: 0091-3057; 1873-5177
• DOI: 10.1016/S0091-3057(97)00560-1

The selective functions of D
3 receptors in the brain are still poorly understood, mainly because all the ligands active at dopamine D
3 receptors have also a high affinity for the D
2 receptors. However, it is possible to study selectively D
3 receptor function because some brain structures, such as the islands of Calleja, contain D
3 and not D
2 receptors. The position of the island of Calleja Magna in the rat brain makes it possible to inject dopamine D
3 ligands into the vicinity of these D
3 receptors, and to study their behavioral role, with no concomitant action on D
2 receptors. We studied the effects on body temperature and on locomotion of unilateral microinjections of D
2/D
3 receptors ligands into the island of Calleja Magna and into the adjacent nucleus accumbens. The results show that D
3 agonists injected into the island of Calleja Magna decrease body temperature and that this effect is potentiated by simultaneous injection of the D
1 agonist SKF 38393. D
3 agonists have no effect on locomotor activity in the island of Calleja Magna. In the nucleus accumbens, the D
3 agonists have only weak effects on body temperature, but, when associated with a D
1 agonist, strongly stimulate locomotor activity. The effects on body temperature of unilateral microinjections of dopamine agonists into unilaterally dopamine-depleted animals are the same as those in nondepleted ones. This indicates that the D
3 receptors are localized postsynaptically in the island of Calleja Magna.