European Journal of Pharmacology, 184 (1990) 179-183 179 Elsevaer EJP 20670 Short communication Involvement of vasopressin in the cardiovascular effects of quinpirole Christine Damase-Mlchel 1, Jean-Louis Montastruc 1, Mane-Antoinette Tran :, Claude Gharlb 2, Gluslalne Geelen 2 and Paul Montastruc 1 t Laboratolre de Pharmacologte Mddzcale et Chmque, INSERM U317, Facult~ de M~decme, 37 Alldes Jules-Guesde, 31073 Toulouse C~dex, France and 2 Laboratolre de Phystologte, Facult~ de Mddecme Grange Blanche, 8 Avenue Rockfeller, 69373 Lyon C~dex, France Recetved 29 May 1990, accepted 5 June 1990 The effects of qumptrole, a specific dopanune D 2 receptor agomst, were investigated on cardxovascular responses and plasma levels of catecholamlnes and vasopressm m two groups of conscious dogs (1) control dogs and (2) dogs with chabetes mslpMus 0 e ammals surgically deprived of vasopressln) In normal dogs, i v qulnplrole (30 #g/kg) ehc~ted a decrease in blood pressure assocaated vath a nse m both plasma catecholamme and vasopressm levels In dogs with dmbetes mslptdus, i v qumplrole mduced a more marked decrease m blood pressure than m normal dogs Qumplrole did not change plasma noradrenalme and vasopressm levels m dogs with dmbetes mslpldus The present study demonstrates that the decrease m blood pressure ehclted by qumpxrole is assocmted with an mcrease m vasopressm release, wtuch counteracts the hypotenslve effect of the the dopanune D 2 receptor agomst Qtunplrole, [ArgS]vasopressm (AVP), Catecholamlnes, Dmbetes msxpldus, Blood pressure, Doparmne 1. Introduction The involvement of dopamlne D 2 receptors m the regulation of blood pressure has been dis- cussed in the hterature (Montastruc et al, 1990) However, recent studies using qmnp~role, a specific D 2 receptor agonlst, indicate that two mare mech- amsms are involved m the hypotenslve acUon of qumplrole firstly, a peripheral depressor action (mhlbmon of noradrenerg~c neurotransmlss~on xaa D 2 receptors located at a presynapttc level and/or autononuc gang, ha), and secondly, a central pres- sor component (revolving an increase m sym- patheuc tone) The relatwe importance of these two components may vary according to the experi- mental condxtlons (anesthesm, species, route of Correspondence to C Damase-Mlchel, Laborato~re de Phar- macologle M&hcale et Chmque, INSERM U317, Facult6 de M6decme, 37 All~es Jules-Guesde, 31073 Toulouse C&lex, France admlmstratxon), as suggested by Nagahama et al (1987) m rats and Damase-Mxchel et al (m press) m dogs Nagahama et al (1987) also suggested a role for vasopressm m the cardiovascular effects of qumplrole Tlus observation and the confhctmg results on the effects of D 2 agents on vasopressm release (Rack6 et al, 1984, Ctuodera et al, 1986) led us to compare the effects of qump:role on the cardxovascular responses as well as plasma catecholamlne and vasopressln levels in two groups of conscious dogs (1) normal control dogs and (2) dogs with diabetes mslp:dus 2. Materials and methods 2 1 Experimental protocol The effect of qumplrole was examined m six conscious normal dogs (13-20 kg body weight) and stx conscious dogs with diabetes mslpldus (15-24 0014-2999/90/$03 50 © 1990 Elsewer Science Pubhshers B V (Biomedical Division)