S167

ANDROGENIC REGULATION OF GAP JUNCTION mRNA EXPRESSION IN THE MOTONEURONS OF LUMBAR SPINAL CORDS IN ADULT MALE RATS. AKIRA MATSUMOTO (11, YASUMASA ARAI cl), AKIHISA URANO (2) AND SUSUMU HYODO+ (31, 71) Department of Anatomy, Juntendo University School of Medicine, Hongo, Tokyo 113, (2) Department of Molecular Biology Ocean Research Institute, University of Tokyo, Nakano, Tokyo 164, (3) Departmint of Biology, College of Arts and Sciences, University of Tokyo, Meguro, Tokyo 153, Japan.

Gap junctions are considered to play an important role in metabolic and electrical coupling between neurons. Androgenic influence on the expression of mRNA for gap junction protein was examined in the androgen-sensitive motoneurons in the spinal nucleus of the bulbocavernosus (SNB) by using in situ hybridiza- tion. Adult male rats (Wistar) were castrated and implanted with Silastic tubes containing testosterone or nothing. Animals were sacrificed 4 weeks later. A complementary DNA encoding rat liver gap junction protein (connexin 32, a gift from Dr. D.A. Goodenough) was applied on paraffin sections of the lumbar spinal cords. Autoradiographic signals for gap junction mRNA were found to be local- ized on the somata and proximal dendrites of the SNB motoneurons. The number of signals per motoneurons in castrates was significantly smaller than that in controls. This change was prevented by testosterone replacement. These results suggest that androgen regulates the expression of gap junction gene in the SNB motoneurons.

DISTRIBUTION OF c-fos mRNA POSITIVE CELLS IN THE HYPOTHALAMUS IN RATS INJECTED WITH HYPERTONIC SALINE, MITSUKO HAMAMURA', AND GARETH LENG', 'Dept. of Jichi Medical School Minamikawachi-machi --- -----_1_ Tochic& 329-04 Jam- __---_I----- -------L- -------- Institute of Animal Physiology and Genetics Research, Cambridge CB2 4AT, U.K.

We have sought to know whether or not c-fos mRNA expression is detected in the hypothalamus after hypertonic stimulus. Male rats were given hypertonic saline (1.5 M, 18 ml/kg, i.p.) and decapitated 30 min later. The brain sections (20 urn) were hybridised with 35 S-labelled anti-sense oligonucleotide probe specific to rat c-fos mRNA. The sections were-dipped in the autoradiographic emulsion and exposed for 9 weeks. The silver grains were distributed over most of the cells in the supraoptic nucleus, circular nucleus and both magno- and parvo-cellular part of the paraventricular nucleus. c-fos mRNA positive cells were scattered in the circumventricular organs (subfornical organs, AV3V regions and median preoptic nucleus), lateral septal nucleus, bed nucleus of the stria terminalis, dorsomedian thalamus and ventrolateral nucleus. No positive cells was found in rats injected with normal saline. These results indicate that c-fos mRNA expression is induced in the brain area which is involved in osmoregulation.

THYROIDECTOMY INDUCES FOS-LIKE IMMUNOREACTIVITY IN THE PARVOCELLULAR PARAVENTRICULAR HYPOTHALAMIC NUCLEUS OF THE RAT. NORIYUKI KOIBUCHI=, SADAO YAMAOKAI and MITSUO SUZUKI2 lDepartment of Physiology. Dokkyo University S&&i of Medicine, Mibu, Tochigi 321-02, Japan and =Institute of Endocrinology, Gunma University, Maebashi 371, Japan.

The expression of Fos-like immunoreactivity (IR) was examined in the adult rat hypothalamus as a function of surgical thyroidectomy (TX). Male Sprague Dawley rats (250-300 g) were used throughout. One, 3 and 6 days after surgery, rats were sacrificed by transcardial perfusion with 4 % paraformaldehyde. Blood was col- lected and plasma levels of thyrotropin (TSH) was subsequently measured. Brain was removed and 30.um frozen sections were cut and processed for Fos im- munocytochemistry. Within 6 days after TX, a specific increase in the number of Fos-like IR in cells in the parvocellular paraventricular nucleus of the hypothalamus (pPVN) was observed. In contrast, no change in the number of Fos- like IR cells was observed within any of the other brain areas examined TX. The time course for the effect of TX in the pPVN correlated with changes in the plasma levels of TSH. Furthermore, double-immunostaining for Fos and TRH showed that the increase in the number of Fos-IR cell following TX is induced specifi- cally within TRH-containing neurons located in the pPVN.