Acta Physiol Scand zyxwvut 1987, 130, 307-31 I zyxwvutsrqp Effects of subacute treatment with toluene on cerebrocortical zyxw a- and P-adrenergic receptors in the rat. Evidence for an increased number and a reduced affinity of P-adrenergic receptors zy K. FUXE, M. MARTIRE, G. VON EULER, L. F. AGNATI,* T. HANSSON,t K. ANDERSSON, zyxwvu J.-k GUSTAFSSONt and A. HARFSTRAND Departments of Histology, Karolinska Institute, Stockholm, Sweden, *Human Physiology, University of Modena, Italy, and tMedical Nutrition, Karolinska Institute, Huddinge University Hospital, Huddinge, Sweden FUXE, K., MARTIRE, M., VON EULER, G., AGNATI, L. F., HANSSON, T., ANDERSSON, K., GUSTAFSSON, J.-A. zyxwvuts & H~RFSTRAND, A. Effects of subacute treatment with toluene on cerebrocortical a- and /3-adrenergic receptors in the rat. Evidence for an increased number and a reduced affinity ofi3-adrenergic receptors. Acta PhysiolScand 130,307-31 I. Received 6 October 1986, accepted 19 January 1987. ISSN 0001-6772. Departments of Histology, Karolinska Institute, Stockholm, Sweden, Human Physiology, University of Modena, Italy, and Medical Nutrition, Karolinska Institute, Huddinge University Hospital, Huddinge, Sweden. Subacutetreatment with toluene (80-1 zyxw 500 p.p.m.) produces a dose-dependent reduction of affinity and increase in density of the /3-adrenergic antagonist [3HIdihydroalprenolol binding sites in the frontoparietal cortex of the male rat, while the binding characteristics of a,-adrenergic ([3H]WB 4101) and a,-adrenergic ([3Hlp-aminoclonidine) binding sites in the same region is unaffected by this treatment as evaluated in vitro. Therefore, it is suggested that the cortical /3-adrenergic receptors are particularly vulnerable to the action of toluene in vivo. It is speculated that as a result cortical /3-adrenergic neurotransmission may be altered following exposure to low concentrations of toluene, possibly related to the physico-chemical properties of toluene, leading to changes in membrane fluidity. Key words ; /I-, a,-and a,-adrenergic receptors, p-[3H]aminoclonidine, [3H]dihydroal- prenolol, frontoparietal cortex, rat, toluene, [3H]WB 4101. Previous studies have demonstrated that sub- acute treatment with toluene in the rat leads to a reduced affinity in [3H]~-hydroxytryptarnine ([~HIs-HT) binding sites in the frontoparietal cortex and a reduced affinity in striatal [3H]spiperone binding sites (Celani et al. 1983). It was suggested that these effects observed in vitro following in vivo treatment with toluene reflect a reduced transmission at dopamine receptors of the D, type in the striatum and in s-HT,-receptors in the frontoparietal cortex, Correspondence : Professor Kjell Fuxe, Department of Histology, Karolinska Institute, Box 60400, S-104 01 Stockholm, Sweden. since the synapses concerned may have to operate at higher concentrations of DA and s-HT, respectively. In the present paper, the same exposure to toluene in vivo has been performed to analyse how toluene modulates the binding characteristics of [3H](z-(2,-6-dimethoxy) (phenoxy-ethy1amino)-meth yl-benzodioxan) ([3H]WB 4101) binding sites labelling a,- adrenergic receptors, of p-[3H]aminoclonidine ([3H]PAC) binding sites labelling a,-adrenergic receptors and [3H]dihydroalprenoloI ([3H]DHA) binding sites labelling p-adrenergic receptors, in the frontoparietal cortex of the rat (Bylund & Snyder 1976, U’Prichard et al. 1977). 307