View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Digital.CSIC The Journal of Neuroscience, August 1994, 14(8): 4839-4846 Dopaminergic Regulation of the Serotonergic Raphe-Striatal Pathway: Microdialysis Studies in Freely Moving Rats Sergi Ferre, Roser Cartes, and Francesc Artigas Department of Neurochemistry, Centro de Investigacibn y Desarrollo, C.S.I.C., 08034 Barcelona, Spain Morphological evidence demonstrates the existence of do- The dorsal raphe nucleus(DRN) (B6 and B7 areasof Dahlstrom paminergic afferent pathways and dopamine (DA)-contain- and Fuxe, 1964) is a morphologically well-defined structure of ing neurons in the dorsal raphe nucleus (DRN). In a recent the midbrain that contains, by far, the highest number and report, a DA D,-like receptor-mediated regulation of sero- concentration of serotonergic (5HT) cell bodies of the mam- tonin (5-HT) extracellular concentration in DRN has been malian brain (Wiklund et al., 198 1; Descarries et al., 1982). found. Given the existence of somatodendritic 5-HT,, au- Serotonergic neurons from the dorsal raphe project mainly to toreceptors in the DRN, changes of the extracellular con- the basalganglia, particularly the striatum (dorsal and ventral), centration of 5-HT in the vicinity of cell bodies and dendrites the substantianigra (SN), and the ventral tegmental area (VTA) may be relevant for the control of the activity of ascending (A9 and A10 areas of Dahlstrom and Fuxe, 1964) (Van der serotonergic pathways. In the present brain microdialysis Kooy and Hattori, 1980; Herve et al., 1987) and to the frontal study we have used a chromatographic method (HPLC) en- cortex (O’Hearn and Molliver, 1984). These areasare involved abling the simultaneous measurement of DA, 5-HT, and their in the parallel processing of motor function (Alexander and main metabolites dihydroxyphenylacetic acid (DOPAC) and Crutcher, 1990) and are the source of and targets for the mes- 5-hydroxyindoleacetic acid (5-HIAA). The presence of a neu- encephalicdopaminergic systems (Bjorklund and Lindvall, 1984). ronal pool of DA within the DRN was revealed by the local These morphological data suggestthat DRN serotonergic neu- infusion of amphetamine (10 PM), which significantly in- rons modulate the function of brain dopaminergic systems.In- creased the extracellular concentration of both amines. The deed, dopamine (DA)-containing structures display moderate local striatal infusion (10 PM) of the selective DA D,-like to high densities of several 5-HT receptor subtypes (5-HT,,,,,, agonist SKF-38393, the selective DA D,-like agonist quin- 5-HT,, 5-HT,) (Pazos and Palacios, 1985; Pazos et al., 1985; pirole (LY 171,555), or the nonselective DA agonist apo- Waeber et al., 1989, 1990; Hoyer, 1990) and there is functional morphine markedly decreased DA and DOPAC extracellular evidence of a 5-HT-mediated regulation of mesencephalicdo- concentrations and failed to modify 5-HT or 5-HIAA in the paminergic systems, both at the somatodendritic (Nedergaard striatum, indicating the lack of terminal (striatal) control of et al., 1988; Guan and McBride, 1989) and at the terminal level 5-HT release by dopaminergic transmission. In contrast, the (Blandina et al., 1989; Benloucif and Galloway, 1991; Chen et systemic administration of apomorphine (2.8 wmol/kg, s.c.) al., 1991; Parsonsand Justice, 1993). significantly increased the extracellular concentration of 5-HT Less is known, however, about a possibledopaminergic reg- in the DRN and decreased it in the striatum. The reduction ulation of serotonergic DRN neurons, despite morphological of striatal 5-HT extracellular concentration was prevented evidence indicating the existence of projections from SN and by the previous administration of the selective 5-HT,, re- VTA to the DRN (Afifi and Kaelber, 1965; Pasquieret al., 1977; ceptor antagonist WAY 100135 (17.6 rmol/kg, s.c.), which Sakai et al., 1977; Lee and Geyer, 1984; KalCn et al., 1988) and by itself did not change extracellular 5-HT in striatum. These of DA-containing neurons within the DRN (Hokfelt et al., 1976; results support that dopaminergic neurotransmission inhib- Geffard et al., 1987; KalCn et al., 1988). Also, the DRN contains its the activity of DRN-striatal neurons by increasing 5-HT a fairly high density of DA D,-like but not of DA D,-like re- extracellular concentration in DRN and, consequently, by ceptors (Bouthenet et al., 1987; Palaciosand Pazos, 1987). Fur- increasing somatodendritic 5-HT,, autoreceptor stimulation thermore, electrophysiological studieshave shown that the elec- in this nucleus. trical stimulation of SN induces cessation of firing of DRN [Key words: dorsal raphe nucleus, striatom, serotonin, do- neurons (Stern et al., 1981; for review, see Aghajanian et al., pamine, dopamine D,-like receptors, dopamine D,-like re- 1987; Jacobs and Azmitia, 1992). ceptors, serotonin 5-HT,, receptors, in vivo microdialysis] The study of the complex interrelationships between both aminergic systemsis relevant for understandingthe serotonergic changes occurring in neurological diseaseswhere DA is the Received Sept. 30, 1993; revised Jan. 25, 1994; accepted Feb. 8, 1994. transmitter primarily involved (e.g., Parkinson’s disease)(Scat- This work was supported by grants from the Fondo de Investigaci6n Sanitaria ton et al., 1984; Cross, 1988). Besides,DA-5-HT interactions (FIS 92/0268) and the EEC (STEP contract CT9 l-005). We gratefully acknowledge the technical assistance of Josefa Torres and Letizia Campa. We thank Wyeth are thought to play a role in the mechanismof action of atypical Research UK (Maidenhead, UK) for the supply of WAY 100 135. Citalopram was neuroleptics (Tamminga and Gerlach, 1987; Meltzer, 1992)and a generous gift of Lundbeck (Copenhagen, DK). dopaminergic transmission appears to participate in the 3,4- Correspondence should be addressed to Dr. Francesc Artigas, Department of Neurochemistry, C.S.I.C., Jordi Girona 18-26, E-08034 Barcelona. methylenedioxyamphetamine (MDMA)-induced degeneration Copyright 0 1994 Society for Neuroscience 0270-6474/94/144839-08$05.00/O of serotonergic terminals (see McKenna and Peroutka, 1990, 4840 Fern5 et al. - Dopamine Regulation of RaphsStriatal Serotonin Pathway r 1 I I 2 4 6 8 min Figure 2. HPLC trace of a basal (predrug) striatal dialysatesample showingthe presenceof DA, DOPAC. S-HT, and 5-HIAA. Absolute amountsof thesecompounds in this sample(I 5 11)of DA, DOPAC, 5-HT, and 5-HIAA were (in fmol) 175, 185,225,16, and 22.560,re- spectively. for review). Using the microdialysis technique, we recently found a DA D,-like receptor-mediated regulation of 5-HT extracel- lular concentration in the DRN of unanesthetized rats. Local infusion of the nonselective DA receptor agonist apomorphine or the selective DA D,-like receptor agonist quinpirole induced an increaseof extracellular 5-HT in the DRN that was antag- onized by the DA D,-like receptor antagonist raclopride, but not by the DA D,-like antagonist SCH 23390 (Ferre and Artigas, 1993). The existence of somatodendritic S-HT,, autoreceptors that inhibit electrical activity (Sprouse and Aghajanian, 1987, 1988) S-HT synthesis(Hjorth and Magnusson, 1988; Hutson et al., 1989; Invernizzi et al., I99 I), and 5-HT releasein pro- jection areas(Hutson et al., 1989; Sharp et al.. 1989a; Bonvento et al., 1992; Adell et al., 1993) is well documented (Pazos and Palacios, 1985: Verge et al., 1986; Sotelo et al., 1990).Therefore, an increaseddopaminergic transmission within the DRN may inhibit the activity of ascending DRN serotonergic neurons through an enhancementof 5-HT extracellular concentration in DRN and further activation of 5-HT,, autoreceptors. Indeed, pharmacologically induced increasesof extracellular 5-HT in the raphe nuclei reduce terminal 5-HT synthesisand/or release, as measuredwith the push-pull cannula in the cat (Becquet et al., 1990) or in riro microdialysis in awake, freely moving rats (Adell and Artigas, I99 I). In the present study, we have examined the effects of dopa- minergic agentson extracellular 5-HT in the DRN and DA and 5-HT in the striatum. The data obtained support the view that + Fl.igLlrcI. Locationof the dialysisprobes. .4. Photomicrographfrom a cresylviolet-stained section through the DRN (urea delirnmd b.v dots) showing the track left by the microdialysisprobe. The schetnatrcdruwing ofthc probe represents its actual size and position.The dialysismem- brane corresponds to the part between arrowheuds and the crosshatched urea is the tip of the probe(epoxy resin).B, Dark-heldphotomicrograph from an autoradiogram of the DRN at a level similar to that in A. Serotonergiccell bodieshave beenlabeled with a “S-oligonucleotide directedagainst the 5-HT transportermRNA by rn srtu hybridization as describedelsewhere (Cartes et al., 1993). C, Section through the striatum showing the track left by the microdialysis membrane (arrow). Scalebar: 250 wrnfor A and B, I mm for C. The Journal of Neuroscience, August 1994, 14(8) 4841 an increaseddopaminergic activity results in opposite changes 200 l -•DA of extracellular 5-HT in DRN and striatum. A-A 5-HT 175 I - 1 Materials and Methods z -g 150 .4nima/s. Male Wistar rats weighing 290-3 10 gm were used. They were > housed four per cage and kept in a controlled environment (I 2 hr light/ dark cycle and 22 * 2°C room temperature). Food and water were : 125 provided ad libitum. Animal care followed the Spanish legislation on “Protection ofAnimals Used in Experimental and Other Scientific Pur- poses,” in agreement with the European (E.E.C.) regulations (O.J. of E.C. L358/1 18/12/1986). Surgery. Concentric dialysis probes were made as previously de- amphetamine scribed (Adell and Artigas, 1991), with the exception that the length of 50 ! I the membrane exposed to the brain tissue was either I.5 mm or 4.0 0 1 2 3 4 5 6 7 8 9 10 mm long (0.25 mm o.d.). Before implantation, rats were anesthetized with so&urn pentobarbital (60 mg/kg, i.p.) and placed in a stereotaxic sample (30 min/somple) frame.