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ROLE OF THE CENTRAL MONOAMINERGIC SYSTEM IN THE CONTROL OF ARTERIAL BL(3)D PRESSURE IN THE RAT. MASAMI N - ~ * . . ~ S A S H ~ OGAWA*, SHUNICHI MAE~IL~A*, NAOKO TAKAMI*, KAZUNOBU SUG~WARA*, MASAYORI OZAKI, TERU.kKI KAWANO*, YUHZO FUJITA* and KAZUO I~IORI*. 2nd Dept. Pharmacol . and Dept. ~Teurosurgery, Sch. Med. , Nagasaki Univ. , Na~,~asak~ 8.52.

Normotensive ra t s : 6-Hydroxydopamine (6-OHDA), which is known to degenerate norepinephrine (NE) contaJn!~g neurons specifically~ ~ , ~ujected b i la tera l ly into the nucleus locus coeruleus (LC) at a dose of 6 - ~ ~ ~g. ~ e r the m . | e ~ ; ~ blood p r e s s u r e (BP) and hear t ra te increased significantly ah~, ,.lasted ~or about 12 days. Two weeks af ter the injection of 6-OHDA into the LC, the cont~nts of both serotonin (5~HT) and 5- H I ~ in the spinal cord and c e r e b r a l cor tex inc reas ~d significantly, a ~ the turnover ra te of 5-HT was also found to be increased . These resu l t s s~ggest tb~J/~ 5-HT containing neurons may be involved in the neural mechPuism which depressed BP.

3pontaneously hyper tens ive ra t s (SItRs): 6-hydrox--rlopa (6-OHDOPA) was injected on the 19th and 21st days of gestation. The NE content~. ~; d~e bra in cor tex and spinal cord at 12 w e e ~ of age ~ e r e markedly lower than that of non-t reated SHRs. The effect of a - methyldopa (a-MD) was significantly sma l l e r in 6-OKDOPA t rea ted S KRs and the content of a -methylnorepinephr ine (~-MeNE) in ~ e spinal cord was significantly lower in those SHRs. These rvsul ts appear to suggest that NE contai~dng neurons a r e involved in the control of BP at the level of the sp i ra l cord as wel l as~ im the lower bra in s tem.

P-RECEPTOR IN NORADRENERGIC INK[BITION OF SPII~AL TRIGEMINAL NUCLEUS NEURONS. MASASHI SASA and SHUJI TAKAORI. Dept. P h a r m a c o l . , Fac. Med. , Kyoto Univ. , Sakyo-kut Kyo~o 606.

The study was per formed on cats anesthet ized with a -ch lora lose to determine whether or not the noradrenerg ic inhibition of spinal trige~nmal nucleus (STN) neurons from the locus coeruleus (LC) is mediated by ~-adrenergic r ~ e p t o r s . Noradrenalinep isoproterenol~ sotalol, and glutamate were iontophoretically applied using a seven- ba r re led micropipet te at tached to a s i lver wi re mic roe lec t rede f~r recording STN neuron activiLy~ The effects of the drugs and s t imul i to the LC preceding the tes t s t imulus were examined in STN re lay neurr,ns, which were identified by orthodromic s t imulat ion of the infer ior a lveolar nerv~ and ant idromic s t imulat ion of ~le medial lemniscus .

Isoproterenol up t~ 200 nA inhibited the orthodromic spike generat ion of the STN re lay neurons as did noradrenaIine up to 200 nA and the LC c~mditioning st imulation, but failed to affect the ant idromic spike. Sotalol up to 200 nA antagoi~ized the inhibition of the or thedromic spike produced by ioatophoretic isoprotervnol and noradrenal ine as well ~s LC conditioning st imulat ion. However, glutamate- induced ~pike fir ing of the re lay neuron was r a r e ly affected by isopro~,erenol and noradrenal in~.

These resu l t s ~trongly suggest that the inhibition producvd by LC st imulation on t r ansmis s ion of the STN r e h y neurons is mediated by # - recep to rs probably located in the afferent t e rmina ls .