Quantification of 5-hydroxytryptamine1A receptors in the cerebellum of normal and X-irradiated rats during postnatal development.
5-Hydroxytryptamine1A receptors were studied in rats during the first postnatal month in the normal cerebellum and in the granule cell-deprived cerebellum produced by X-irradiation at postnatal day 5. Quantitative autoradiographic studies on sagittal sections of cerebellar vermis, using [1251]BH-8-MeO-N-PAT as radioligand or specific anti-receptor antibodies, revealed that 5-hydroxytryptamine1A receptors existed in the molecular/Purkinje cell layer but at variable density from one lobule to another. Thus, in both normal and X-irradiated rats, the posterior lobules were more heavily labelled than the anterior ones, and the density of 5-hydroxytryptamine1A sites decreased progressively in all the cerebellar folia down to hardly detectable levels at postnatal day 21. However, the intensity of labelling remained higher at postnatal day 8 and postnatal day 12 in X-irradiated rats than in age-paired controls. Measurements of [3H]8-OH-DPAT specific binding to membranes from whole cerebellum confirmed that the density of 5-hydroxytryptamine1A sites per mg membrane protein (Bmax) was higher in X-irradiated animals than in age-paired controls. However, on a "per cerebellum" basis, no significant difference could be detected between the total number of 5-hydroxytryptamine1A sites, which progressively increased in both control and X-irradiated animals during the first postnatal month. These results therefore show that 5-hydroxytryptamine1A receptors are not located on developing granule cells. The progressive decrease in 5-hydroxytryptamine1A receptor density during the first postnatal month did not reflect a transient expression of 5-hydroxytryptamine1A receptors in the cerebellum of newborn rats, but resulted from the progressive "dilution" of these sites in this growing structure. The higher density of 5-hydroxytryptamine1A sites in X-irradiated rats simply reflected a lower "dilution" due to the delayed growth of the cerebellum in these animals.
Matthiessen
L
L
Département de Cytologie, CNRS UA 1199, Université Pierre et Marie Curie, Paris, France.
Daval
G
G
Bailly
Y
Y
Gozlan
H
H
Hamon
M
M
Vergé
D
D
D000375:Aging / Q000378:metabolism*; D000818:Animals; D001345:Autoradiography; D002462:Cell Membrane / Q000378:metabolism; D002531:Cerebellum / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects*; D007150:Immunohistochemistry; D007457:Iodine Radioisotopes; D008024:Ligands; D011689:Purkinje Cells / Q000378:metabolism / Q000528:radiation effects; D051381:Rats; D017208:Rats, Wistar; D011985:Receptors, Serotonin / Q000378:metabolism* / Q000528:radiation effects*; D013764:Tetrahydronaphthalenes / Q000378:metabolism; D014965:X-Rays
D007457:Iodine Radioisotopes; D008024:Ligands; D011985:Receptors, Serotonin; D013764:Tetrahydronaphthalenes; C055126:8-methoxy-2-(N-propyl-N-(3'-iodo-4'-hydroxyphenyl)-propionamido-N'-propylamino)tetralin