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Gastric afferents to putative oxytocin-secreting neurons in the hypothalamic paraventricular nucleus — possible involvement of central catecholaminergic pathway
S88
RESPONSES OF CAT HYPOTHALAMIC PARAVENTRICULAR NEDROSECRETORY NEURONS TO RAPBE NUCLEI STIMIJLATION. SEIICHIRO KAWANO*, TOSHIKASA OSAKA, SWICHI KURAKAWA*, AED HIROSHI YAMASHITA, Dept. of Physiol., Univ. of OCCUP. and Environ. Health, Yahatanishi-ku, Kitakyushu 807, Japan Plasma concentration of vasopressin is increased by intraperitoneal administration in rats of a serotonin releaser or a serotonin agonist and this effect is inhibited by a 5-HT2 blocker. There is a serotonergic projection from the midbrain raphe nuclei to the hypothalamic paraventricular nucleus. Therefore we studied the effects of raphe nuclei stimulation on neurosecretory neurons in the paraventricular nucleus of the hypothalamus. Extracellular recordings were made from antidromically identified paraventricular neurosecretory neurons of hemispherectomized cats under pentobarbital anesthesia (35 mg/kg i.p.). Stimulating electrodes were introduced stereotsxically into dorsal, median, and pontine raphe nuclei. Stimulation of the dorsal, median, and pontine raphe nucleus excited 49 out of 160, 42 out of 145, and 10 out of 87 neurons tested, respectively, and inhibited 12 out of 160, 5 out of 145, and 9 out of 87. The typical excitatory response had a fast latency (20~6Oms) with short duration (20-80ms). But there were late excitatory responses with long latency and duration (longer than looms). The excitatory responses were blocked by the 5-HT2 antagonist cyproheptadine (1 mg/kg i.v.) in all 7 neurons tested. It is suggested that there is an excitatory serotonergic input from the midbrain raphe nuclei to the hypothalamic paraventricular nucleus and that the 5-HT2 receptor is involved in this system.
BC PAWVEr?lTuaW@ GASTRIC AFFEHWB TD PUTATIVEOXYlWIN-SECHEIDG IWJROMSINTHH YOICHI UEIl'A*,HIXISHI NUUEUS - poSSIHLE ItW3L~OFCEWHALCA~IC PAl'BWAY-A, Eept. of Physiol., & of Cccup. & hvx KAbEIAN,N?0KIAKAMARp*ANDHIROSHI shu, Japan 807. Health, -sch. of ~ahaZZii~K.ita@u Med. Cur orevious studvhes denunstrated that mutative oxvtccin(OKT)-secretinq neurosecretorv cells in the- hypotbelemi~ paraventricular nucleus (PVN) rec&ve excitatory syr&tic inputs f&n the stanach. l'be present study has been dcne to examine the possibility that catecholeminergic the brainstem is involved in the gastric afferent pathway. Kxtracellular projection fran !Itm recordings were made in rats anesthetized with a mixture of urethane and d-chloralose. effects of electrical stimuleticm( a train of 3 pulses, 0.5 ms duration, 100 Hz, 50-500 ).lA gastric &an&es were examined by means of peristimulus time of the vagal intensity ) histograms. To destroy the catecholamine terminel plexus in the WM, microinjection of neurotoxin 6-hydroq&pamine(6-OHW,wA) ( 5 ).q in 0.2 pl saline containing 0.02 % L-ascorbic acid ) or salineascorbate vehicle into the dorsolateral part of the PVN was performad approximately lo-24 hours by a before the experiment. Destruction of the PVN cetecholamine terminalplexuswas anfirmed catecholsmine histofluorescence technique. Electrical stimulation of the gastric branches excited 17 of 26 continuously firing cells in rats pretreated with vehicle, while only 3 out of 20 neurcms in rats pretreated with 6-OHDA. These results suggest that ths central catecholaminergic projection to putative OXT-secreting mrons in the PW may, at least in part, be involved in mediating ths excitatory effects fran the stamch.
ENDOTHNLIN EXCITES NEURONS IN THE ANTEROVENTRAL THIRD VEKTRICLE(AV3V) REGION OF RAT HYPOTHALAMIC KIYOTOSHI INFKAGA --9 MASANORI KASAI SLICE PREPARATIONS. HIROSHI YAMASHITA, --f SHIGEKI YAMAWOTO --9 Denartment of lat phy siolog~, Univ. of Occup. and Environ. Health, Yehatanishi-ku. Kitakyushu 807, Japan. Endothelin(ET) is a novel and potent vasoconetrictor peptide isolated from vascular endothelial cells. High affinity binding sites of ET were observed in the central nervoue systems(CNS) and intracerebroventricular injection of ET increased blood pressure, implying that ET may play an important role as a neuropeptide in the central regulatory system of the autonomic nervous system. To clarify actions of ET on neurons in the CNS, extracellular recordings were made from neurons in the region of the anteroventral third ventricle (AV3V) iporat hsp othalamic slice preparations. -3X10- M. Of 80 AV3V neuron8 tested ET-3 wae applied to the slice at concentrations of 10 14(18X) were excited, four(5%) slightly inhibited, end sixty-two(77X) unaffected threshold concentration to evoke a reeponae in the AV3V neurons was approximately IO-&. z:*t:: the neurons which were excited by ET existed in the rostal part of the AV3V region and near the re ion of the organum vaaculosum lamina terminalis. Excitatory responses to ET were observed in Ca4t-free medium. This result suggests that extracellular calcium ions are not always necessary to elicit ET responses.
RESPONSES OF CAT HYPOTHALAMIC PARAVENTRICULAR NEDROSECRETORY NEURONS TO RAPBE NUCLEI STIMIJLATION. SEIICHIRO KAWANO*, TOSHIKASA OSAKA, SWICHI KURAKAWA*, AED HIROSHI YAMASHITA, Dept. of Physiol., Univ. of OCCUP. and Environ. Health, Yahatanishi-ku, Kitakyushu 807, Japan Plasma concentration of vasopressin is increased by intraperitoneal administration in rats of a serotonin releaser or a serotonin agonist and this effect is inhibited by a 5-HT2 blocker. There is a serotonergic projection from the midbrain raphe nuclei to the hypothalamic paraventricular nucleus. Therefore we studied the effects of raphe nuclei stimulation on neurosecretory neurons in the paraventricular nucleus of the hypothalamus. Extracellular recordings were made from antidromically identified paraventricular neurosecretory neurons of hemispherectomized cats under pentobarbital anesthesia (35 mg/kg i.p.). Stimulating electrodes were introduced stereotsxically into dorsal, median, and pontine raphe nuclei. Stimulation of the dorsal, median, and pontine raphe nucleus excited 49 out of 160, 42 out of 145, and 10 out of 87 neurons tested, respectively, and inhibited 12 out of 160, 5 out of 145, and 9 out of 87. The typical excitatory response had a fast latency (20~6Oms) with short duration (20-80ms). But there were late excitatory responses with long latency and duration (longer than looms). The excitatory responses were blocked by the 5-HT2 antagonist cyproheptadine (1 mg/kg i.v.) in all 7 neurons tested. It is suggested that there is an excitatory serotonergic input from the midbrain raphe nuclei to the hypothalamic paraventricular nucleus and that the 5-HT2 receptor is involved in this system.
BC PAWVEr?lTuaW@ GASTRIC AFFEHWB TD PUTATIVEOXYlWIN-SECHEIDG IWJROMSINTHH YOICHI UEIl'A*,HIXISHI NUUEUS - poSSIHLE ItW3L~OFCEWHALCA~IC PAl'BWAY-A, Eept. of Physiol., & of Cccup. & hvx KAbEIAN,N?0KIAKAMARp*ANDHIROSHI shu, Japan 807. Health, -sch. of ~ahaZZii~K.ita@u Med. Cur orevious studvhes denunstrated that mutative oxvtccin(OKT)-secretinq neurosecretorv cells in the- hypotbelemi~ paraventricular nucleus (PVN) rec&ve excitatory syr&tic inputs f&n the stanach. l'be present study has been dcne to examine the possibility that catecholeminergic the brainstem is involved in the gastric afferent pathway. Kxtracellular projection fran !Itm recordings were made in rats anesthetized with a mixture of urethane and d-chloralose. effects of electrical stimuleticm( a train of 3 pulses, 0.5 ms duration, 100 Hz, 50-500 ).lA gastric &an&es were examined by means of peristimulus time of the vagal intensity ) histograms. To destroy the catecholamine terminel plexus in the WM, microinjection of neurotoxin 6-hydroq&pamine(6-OHW,wA) ( 5 ).q in 0.2 pl saline containing 0.02 % L-ascorbic acid ) or salineascorbate vehicle into the dorsolateral part of the PVN was performad approximately lo-24 hours by a before the experiment. Destruction of the PVN cetecholamine terminalplexuswas anfirmed catecholsmine histofluorescence technique. Electrical stimulation of the gastric branches excited 17 of 26 continuously firing cells in rats pretreated with vehicle, while only 3 out of 20 neurcms in rats pretreated with 6-OHDA. These results suggest that ths central catecholaminergic projection to putative OXT-secreting mrons in the PW may, at least in part, be involved in mediating ths excitatory effects fran the stamch.
ENDOTHNLIN EXCITES NEURONS IN THE ANTEROVENTRAL THIRD VEKTRICLE(AV3V) REGION OF RAT HYPOTHALAMIC KIYOTOSHI INFKAGA --9 MASANORI KASAI SLICE PREPARATIONS. HIROSHI YAMASHITA, --f SHIGEKI YAMAWOTO --9 Denartment of lat phy siolog~, Univ. of Occup. and Environ. Health, Yehatanishi-ku. Kitakyushu 807, Japan. Endothelin(ET) is a novel and potent vasoconetrictor peptide isolated from vascular endothelial cells. High affinity binding sites of ET were observed in the central nervoue systems(CNS) and intracerebroventricular injection of ET increased blood pressure, implying that ET may play an important role as a neuropeptide in the central regulatory system of the autonomic nervous system. To clarify actions of ET on neurons in the CNS, extracellular recordings were made from neurons in the region of the anteroventral third ventricle (AV3V) iporat hsp othalamic slice preparations. -3X10- M. Of 80 AV3V neuron8 tested ET-3 wae applied to the slice at concentrations of 10 14(18X) were excited, four(5%) slightly inhibited, end sixty-two(77X) unaffected threshold concentration to evoke a reeponae in the AV3V neurons was approximately IO-&. z:*t:: the neurons which were excited by ET existed in the rostal part of the AV3V region and near the re ion of the organum vaaculosum lamina terminalis. Excitatory responses to ET were observed in Ca4t-free medium. This result suggests that extracellular calcium ions are not always necessary to elicit ET responses.