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1831 Catecholaminergic regulation of spinally projecting serotonin neurons in the rat rostral ventromedial medulla oblongata
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A ROLE OF NITRIC OXIDE-- CYCLIC GMP PATHWAY IN THE MECHANISM OF PERIPHERAL HYPERALGESIA. AKIHIRO NAKAMURA, MANABU FUJITA AND HIROHITO SHIOMI,
Dep. of Pharmacol., Fac. of Pharmacy and Pharmaceut. Sci., Fukuyama University, Gakuen-cho, Fukuyama 729-02, Japan. Recently, we have demonstrated that nitric oxide (NO) - cyclic GMP (cGMP) pathway is involved in the mechanism of bradykinin (BK) -induced peripheral hyperalgesia. In the present study, we investigated whether NO - cGMP pathway also plays a role in production of hyperalgesia induced by other chemical mediators. Nociceptive thresholds of rat hind paw were measured by a paw-pressure test. Intradermal administration of adenosine, serotonin (5-HT) or prostaglandin E 2 (PGE2) pr6duccd significant hyperalgesia. Adenosine-induced hyperalgesia was significantly blocked by simultaneous administration of N%nitro-L-arginine methyl ester (L-NAME), a NO synthase inhibitor. However, L-NAME did not produce any significant effect on 5-HT and PGE 2 - induced hyperalgesia. These results show that activation of NO - cGMP pathway was involved in the mechanism of BK- and adenosine - induced hyperalgcsia, but not 5-HT- and PGEz- induced one. Taking our previous findings into consideration, activation of cGMP second messenger system, which probably participates in production of peripheral hyperalgesia, is mediated via either NO or other messenger systems.
"183]
CATECHOLAMINERGIC REGULATION OF S P I N A L L Y PROJECTING SEROTONIN NEURONS IN THE R A T ROSTRAL V E N T R O M E D I A L MEDULLA OBLONGATA. M A S A K I T A N A K A I, H I T O S H I OKAMURA 2, YOSHITAKA T A M A D A 2 AND YASUHIKO I B A T A 2, Dept. of 1 A n e s t h . a n d ' 2 A n a t . , K v o t o Pref. Univ. of Medicine, K a w a r a m a c h i - H i r o k o i i , K v o t o 602. Japan
The midline of rostrai ventral medulla (RVM) is the portion in which man)' serotonin neurons (nucleus raphe magnus and rostral nucleus raphe pallidus) and dense catecholamine (noradrenaline and, to a lesser degree, adrenaline ) fibers are distributed. These serotonin neurons are known to project to the spinal cord and to be involved in pain modulation and cardiovascular pressure control. In this study, we have investigated the connection between spinally projecting serotonin neurons and catccholamincrgic fibers in the rat RVM by light and electron microscopic immunocytochcmistry. First, light microscopic immunocytochemistry using triple labeling method revealed that serotonin-immunorcative (IR) neuron (visualized by avidin-biotin peroxidase complex and diaminobenzidine) which contains retrograde tracer (cholera toxin B subunit) injected in the cervical cord (labeled by FITC) was observed to be intimately surrounded by tyrosine hydroxylase (TH)-IR fibers (labeled by Rhodamine). Second, Silver-gold intensified TH-IR axon terminals were ftmnd to make synaptic contacts with serotonin-IR neuronal perikarya and dendrites by double labeling immunoelectron microscopy. These results suggest that spinally projecting serotonin neurons, presumed to be involved in pain modulation or cardiowtscular control are directly regulated by catecholamincrgic neurons at the level of RVM.
] 832
INNERVATION OF THE TOOTH PULP BY THE MESENCEPHALIC TRIGEMINAL N U C L E U S , AS D E M O N S T R A T E D B Y R E T R O G R A D E T R A N S P O R T O F H R P A N D WALLERIAN AXONAL DEGENERATION. KENICHI YOSHINO AND NIICHIRO AMANO, Dept. o f Oral Neurosci., K y u s h u Dent. Col., K i t a k y u s h u 803, Japan. Although several investigators searched the trigeminal ganglion and mesencephalic trigeminal nucleus (MTN) for labeled neuronal cell bodies after HRP injection into the tooth pulp (TP) in a variety of mammals, all but Chiego et al. ('80) and us (Amano, et al., '87; Yoshino, et al., '89) have denied the presence of labeled cell bodies in the MTN. In our studies, following application of a total of 1-2,u I of 30% HRP in saline to the unilateral 4 mandibular TPs of the adult cat, dog, monkey, rabbit, and rat, a maximum of 33, 33, 13 labeled neurons have been found in the MTN on *~e side ipsilateral to the application of HRP in the former 3 animals, respectively; whereas no labeled neurons were found in the MTN of the rabbit and rat. The achievement of labeling of TP-neurons of the MTN was considered as a result of previous treatment with prednisolone, an anti-inflammatory synthetic steroid, which-succeeded in neutralizing inhibition of axonal transport of HRP resulting from local pressure effects due to edema formation in the sealed pulp chambers. Surgical destruction of the unilateral MTN in 3 cats resulted in degeneration of substantial numbers of myelinated axons in the upper and lower canine TPs, as well as in the inferior alveolar nerve, on the operated side as compared to.almost no degenerating myelinated axons found on the non-operated side.
A ROLE OF NITRIC OXIDE-- CYCLIC GMP PATHWAY IN THE MECHANISM OF PERIPHERAL HYPERALGESIA. AKIHIRO NAKAMURA, MANABU FUJITA AND HIROHITO SHIOMI,
Dep. of Pharmacol., Fac. of Pharmacy and Pharmaceut. Sci., Fukuyama University, Gakuen-cho, Fukuyama 729-02, Japan. Recently, we have demonstrated that nitric oxide (NO) - cyclic GMP (cGMP) pathway is involved in the mechanism of bradykinin (BK) -induced peripheral hyperalgesia. In the present study, we investigated whether NO - cGMP pathway also plays a role in production of hyperalgesia induced by other chemical mediators. Nociceptive thresholds of rat hind paw were measured by a paw-pressure test. Intradermal administration of adenosine, serotonin (5-HT) or prostaglandin E 2 (PGE2) pr6duccd significant hyperalgesia. Adenosine-induced hyperalgesia was significantly blocked by simultaneous administration of N%nitro-L-arginine methyl ester (L-NAME), a NO synthase inhibitor. However, L-NAME did not produce any significant effect on 5-HT and PGE 2 - induced hyperalgesia. These results show that activation of NO - cGMP pathway was involved in the mechanism of BK- and adenosine - induced hyperalgcsia, but not 5-HT- and PGEz- induced one. Taking our previous findings into consideration, activation of cGMP second messenger system, which probably participates in production of peripheral hyperalgesia, is mediated via either NO or other messenger systems.
"183]
CATECHOLAMINERGIC REGULATION OF S P I N A L L Y PROJECTING SEROTONIN NEURONS IN THE R A T ROSTRAL V E N T R O M E D I A L MEDULLA OBLONGATA. M A S A K I T A N A K A I, H I T O S H I OKAMURA 2, YOSHITAKA T A M A D A 2 AND YASUHIKO I B A T A 2, Dept. of 1 A n e s t h . a n d ' 2 A n a t . , K v o t o Pref. Univ. of Medicine, K a w a r a m a c h i - H i r o k o i i , K v o t o 602. Japan
The midline of rostrai ventral medulla (RVM) is the portion in which man)' serotonin neurons (nucleus raphe magnus and rostral nucleus raphe pallidus) and dense catecholamine (noradrenaline and, to a lesser degree, adrenaline ) fibers are distributed. These serotonin neurons are known to project to the spinal cord and to be involved in pain modulation and cardiovascular pressure control. In this study, we have investigated the connection between spinally projecting serotonin neurons and catccholamincrgic fibers in the rat RVM by light and electron microscopic immunocytochcmistry. First, light microscopic immunocytochemistry using triple labeling method revealed that serotonin-immunorcative (IR) neuron (visualized by avidin-biotin peroxidase complex and diaminobenzidine) which contains retrograde tracer (cholera toxin B subunit) injected in the cervical cord (labeled by FITC) was observed to be intimately surrounded by tyrosine hydroxylase (TH)-IR fibers (labeled by Rhodamine). Second, Silver-gold intensified TH-IR axon terminals were ftmnd to make synaptic contacts with serotonin-IR neuronal perikarya and dendrites by double labeling immunoelectron microscopy. These results suggest that spinally projecting serotonin neurons, presumed to be involved in pain modulation or cardiowtscular control are directly regulated by catecholamincrgic neurons at the level of RVM.
] 832
INNERVATION OF THE TOOTH PULP BY THE MESENCEPHALIC TRIGEMINAL N U C L E U S , AS D E M O N S T R A T E D B Y R E T R O G R A D E T R A N S P O R T O F H R P A N D WALLERIAN AXONAL DEGENERATION. KENICHI YOSHINO AND NIICHIRO AMANO, Dept. o f Oral Neurosci., K y u s h u Dent. Col., K i t a k y u s h u 803, Japan. Although several investigators searched the trigeminal ganglion and mesencephalic trigeminal nucleus (MTN) for labeled neuronal cell bodies after HRP injection into the tooth pulp (TP) in a variety of mammals, all but Chiego et al. ('80) and us (Amano, et al., '87; Yoshino, et al., '89) have denied the presence of labeled cell bodies in the MTN. In our studies, following application of a total of 1-2,u I of 30% HRP in saline to the unilateral 4 mandibular TPs of the adult cat, dog, monkey, rabbit, and rat, a maximum of 33, 33, 13 labeled neurons have been found in the MTN on *~e side ipsilateral to the application of HRP in the former 3 animals, respectively; whereas no labeled neurons were found in the MTN of the rabbit and rat. The achievement of labeling of TP-neurons of the MTN was considered as a result of previous treatment with prednisolone, an anti-inflammatory synthetic steroid, which-succeeded in neutralizing inhibition of axonal transport of HRP resulting from local pressure effects due to edema formation in the sealed pulp chambers. Surgical destruction of the unilateral MTN in 3 cats resulted in degeneration of substantial numbers of myelinated axons in the upper and lower canine TPs, as well as in the inferior alveolar nerve, on the operated side as compared to.almost no degenerating myelinated axons found on the non-operated side.