s43

CHARACTERIZATION AND LOCALIZATION OF VASOPRESSIN BINDING SITES IN RAT BRAIN AND PERIPHERAL TISSUES RYO SAITO, YUKIO TAKANO, YASUHISA NAKAYAMA. AND HIRO-0 KAMIYA, Department of Pharmacology, Faculty of Pharmaceutical Sciences, Fukuoka University, Fukuoka 814-01, Japan.

There is considerable evidence that arginine vasopressin (AVP) may play important roles in the central control of blood pressure and in the memory processes. The two types of AVP receptor (Vl and VZ) have been distinguished based on their respective second messengers. Recently, a nonpeptide and selective Vl antagonist, OPC-21268, was synthesized. The present study was aimed to examine the regional distribution and characterization of Vi and V2

binding sites in rats using the selective antagonist and other drugs. The 3H-AVP binding sites were examined in the membrane preparations from liver, kidney and various brain regions. Specific binding to Vl receptor subtypes were appeared in the liver and the hind brain. The VZ receptor was identified only in the kidney. Now, we are studying on the regional distribution of Vl and VZ receptor in rat brain using quantitative autoradiography.

DISIRIBUTION OF Cq INTHERATHJNDBIWN RYOHACHI ARAI’, DAVID M. JACOBOWIT2?, AND TOSHIHIRO MAEDA’, ‘Department of Anatomy, Shiga University of Medical Science, Otsu 520-21, Japan, and ‘Laboratory of Clinical Science, National Institute of Mental Health, Bethesda, MD 20892, USA

The distribution of the calcium-bindine nrotein (calretinin) in the hindbrain of the rat was examined by an immunoperoxidase -m&hod, using an antiserum against calretinin purified from the guinea pig brain. Calretinin immunoreactivity was found within neuronal elements. The distribution of calretinin-immunoreactive cell bodies and fibers is presented in schematic drawings, and summarized in a table. Major calretinin-immunoreactive neurons were found in the lateral and medial geniculate nuclei, substantia nigra, ventral tegmental area, interpeduncular nucleus, periaqueductal gray, mesencephalic trigeminal nucleus, superior and inferior colliculi, pontine nuclei, parabrachial nucleus, dorsal and laterodorsal tegmental nuclei, cochlear nuclei, vestibular nuclei, medullary reticular nuclei, nucleus of the solitary tract, area postrema, substantia gelatinosa of the spinal trigeminal nucleus, and cerebellum.

7. Enzymes

Neurochemical properties of L-glutamate transport into Xenopus oocytes injected with rat brain mRNA Sfisashi Urushihara, Michihis_a Tohda ~_, and Yasuyuki Nomura, Department of Pharmacology, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060, JAPAN.

Neurochemical properties of brain L-glutamate (Glu) transporter were investigated using Xenopus oocytes injected with rat brain mRNA. The 13H]Glu transport activity into mRNA-injected oocytes was higher than into native oocytes,suggesting reconstitution of functional Glu transporters in oocytes. The c3HlGlu transport activity into mRNA-injected oocytes was sensitive to Na' or CaZ+ and inhibited by pretreatment with ouabain and addition of Glu or tryptophan. The [3HlGlu transport into non-injected oocytes was also inhibited by omission of CaZ', ouabain-treatment and Glu but not bv omission of Na' or addition of tryptophan. It is suggested that brain Glu transporters, which seem to differ from the native Glu transporter, are functionally expressed in oocytes by injection of mRNA.