Mechanisms mediating the brain stem control of somatosensory transmission in the dorsal horn of the cat's spinal cord: an intracellular analysis

Summary The effect of brainstem stimulation was studied on neurones recorded intracellularly in the superficial and deeper laminae of the lumbosacral dorsal horn of the spinal cord in anaesthetised cats. Stimulation in the nucleus locus coeruleus (LC) produced a hyperpolarisation in 4/13 multireceptive neurones and produced a biphasic action consisting of a hyperpolarisation which was followed by a depolarisation in 3/13 neurones. These actions were produced irrespective of whether the multireceptive neurone was located in the superficial or deeper laminae of the dorsal horn. Stimulation failed to produce postsynaptic potentials in the remaining 6/13 multireceptive neurones. The amplitude of hyperpolarisation was increased by the passage of depolarising pulses through the recording microelectrode and decreased by hyperpolarising pulses. Stimulation in other brainstem areas such as, the lateral (FTL), paralemniscal (FTP) and central (FTC) divisions of the tegmental field and the nuclei raphe magnus (NRM) and reticularis magnocellularis (RMc) also hyperpolarised neurones in the dorsal horn. The polarity of hyperpolarisation evoked from some brainstem areas (FTP, FTC, RMc) could be reversed to depolarisation by the passive diffusion of ions from the recording microelectrode containing 3M-KCl. Brainstem (LC, NRM, FTP, FTL) stimulation generated long lasting (700 ms) hyperpolarisation on 4/4 selectively nocireceptive neurones of lamina I. There was, however, no effect on the activity of 5/5 neurones recorded in laminae I/II which in addition to receiving excitatory cutaneous inputs were inhibited by heat stimuli. Stimulation in LC also produced dorsal root potentials (DRPs) and reduced the amplitude of simultaneously recorded excitatory postsynaptic potentials (EPSPs) generated by the activation of primary afferent fibres in 3 multireceptive neurones. It is concluded that inhibition of nociceptive transmission in the spinal cord from LC and other brainstem areas may involve both pre- and postsynaptic mechanisms.     

中缝大核内催产素在大鼠痛行为调制中的作用

目的：探讨中缝大核（NRM）内催产素（OT）在痛行为调制中的作用，及其和内源性5－HT在痛行为调制中的关系。方法：以钾离子透入法引起大鼠甩尾反应的电流强度（mA)为痛行为反应指标，测定动物痛阈，观察NRM内催产素对大鼠痛行为反应的影响。结果：NMR内注入催产素后，大鼠的痛阈明显增加；注入抗催产素血清后，大鼠的痛阈则明显降低。NRM内注入噻庚啶后，可阻断OT镇痛的效应。结论：NRM内的催产素在痛行为调制的复杂过程中发挥着一定作用，且其效应可能是通过内源性5－HT系统中介的。     

Excitation of neuronal function in rabbit caudal ventrolateral medulla elevates plasma vasopressin

Injection of L-glutamate into the caudal ventrolateral medulla of the rabbit caused a dose-dependent increase in plasma vasopressin. Activity of the A1 noradrenergic cells within the caudal ventrolateral medulla appears to excite the vasopressin-secreting neuroendocrine cells within the hypothalamus.     

The nuclei of origin of brain stem enkephalin and substance P projections to the rodent nucleus raphe magnus

The sites of origin of brain stem enkephalin and substance P projections to the rodent nucleus raphe magnus were studied utilizing the combined horseradish peroxidase retrograde transport-peroxidase-antiperoxidase immunohistochemical technique. Several brain stem areas were found to contain both enkephalin- and substance P-like immunoreactive double labeled neurons following injection of horseradish peroxidase into the raphe magnus. Nuclei providing both enkephalin and substance P inputs to the raphe magnus include the nucleus reticularis paragigantocellularis, the nucleus cuneiformis, the nucleus solitarius and the trigeminal subdivision of the lateral reticular nucleus. Enkephalin projections to the raphe magnus were also found to originate from the dorsal parabrachial nucleus, the nucleus reticularis gigantocellularis pars α and from an area which corresponds to the A5 group of Dahlström &; Fuxe. Additional neurons containing substance P-like immunoreactivity and horseradish peroxidase reaction product were identified in the superior central raphe nucleus and the nucleus pontis oralis. The midbrain periaqueductal gray contributes very few enkephalin and substance P fibers to the raphe magnus.The nucleus raphe magnus is a key structure in the intrinsic analgesia system and it has also been implicated in other diverse and non-nonciceptive functions. The present study identifies several brain stem sites which provide enkephalin and substance P input to this raphe nucleus. Several of these nuclei have been implicated in central analgesic mechanisms or in non-nociceptive autonomic functions. The present investigation raises the possibility that these brain stem regions may modulate neuronal activity in the raphe magnus via enkephalin or substance P projections and thus influence the involvement of the raphe magnus in both opiate related mechanisms of pain control and non-nociceptive functions.     

Projections of the bed nucleus of the stria terminalis to the mesencephalon,pons, and medulla oblongata in the cat

Summary Injections of HRP in the nucleus raphe magnus and adjoining medial reticular formation in the cat resulted in many labeled neurons in the lateral part of the bed nucleus of the stria terminalis (BNST) but not in the medial part of this nucleus. HRP injections in the nucleus raphe pallidus and in the C2 segment of the spinal cord did not result in labeled neurons in the BNST. Injections of ³H-leucine in the BNST resulted in many labeled fibers in the brain stem. Labeled fiber bundles descended by way of the medial forebrain bundle and the central tegmental field to the lateral tegmental field of pons and medulla. Dense BNST projections could be observed to the substantia nigra pars compacta, the ventral tegmental area, the nucleus of the posterior commissure, the PAG (except its dorsolateral part), the cuneiform nucleus, the nucleus raphe dorsalis, the locus coeruleus, the nucleus subcoeruleus, the medial and lateral parabrachial nuclei, the lateral tegmental field of caudal pons and medulla and the nucleus raphe magnus and adjoining medial reticular formation. Furthermore many labeled fibers were present in the solitary nucleus, and in especially the peripheral parts of the dorsal vagal nucleus. Finally some fibers could be traced in the marginal layer of the rostral part of the caudal spinal trigeminal nucleus. These projections appear to be virtually identical to the ones derived from the medial part of the central nucleus of the amygdala (Hopkins and Holstege 1978). The possibility that the BNST and the medial and central amygdaloid nuclei must be considered as one anatomical entity is discussed.Abbreviations AA anterior amygdaloid nucleus - AC anterior commissure - ACN nucleus of the anterior commissure - ACO cortical amygdaloid nucleus - AL lateral amygdaloid nucleus - AM medial amygdaloid nucleus - APN anterior paraventricular thalamic nucleus - AQ cerebral aqueduct - BC brachium conjunctivum - BIC brachium of the inferior colliculus - BL basolateral amygdaloid nucleus - BNSTL lateral part of the bed nucleus of the stria terminalis - BNSTM medial part of the bed nucleus of the stria terminalis - BP brachium pontis - CA central nucleus of the amygdala - Cd caudate nucleus - CI inferior colliculus - CL claustrum - CN cochlear nucleus - CP posterior commissure - CR corpus restiforme - CSN superior central nucleus - CTF central tegmental field - CU cuneate nucleus - D nucleus of Darkschewitsch - EC external cuneate nucleus - F fornix - G gracile nucleus - GP globus pallidus - HL lateral habenular nucleus - IC interstitial nucleus of Cajal - ICA internal capsule - IO inferior olive - IP interpeduncular nucleus - LC locus coeruleus - LGN lateral geniculate nucleus - LP lateral posterior complex - LRN lateral reticular nucleus - MGN medial geniculate nucleus - MLF medial longitudinal fascicle - NAdg dorsal group of nucleus ambiguus - NPC nucleus of the posterior commissure - nV trigeminal nerve - nVII facial nerve - OC optic chiasm - OR optic radiation - OT optic tract - P pyramidal tract - PAG periaqueductal grey - PC cerebral peduncle - PO posterior complex of the thalamus - POA preoptic area - prV principal trigeminal nucleus - PTA pretectal area - Pu putamen - PUL pulvinar nucleus - R red nucleus - RF reticular formation - RM nucleus raphe magnus - RP nucleus raphe pallidus - RST rubrospinal tract - S solitary nucleus - SC suprachiasmatic nucleus - SCN nucleus subcoeruleus - SI substantia innominata - SM stria medullaris - SN substantia nigra - SO superior olive - SOL solitary nucleus - SON supraoptic nucleus - spV spinal trigeminal nucleus - spVcd spinal trigeminal nucleus pars caudalis - ST stria terminalis - TRF retroflex tract - VC vestibular complex - VTA ventral tegmental area of Tsai - III oculomotor nucleus - Vm motor trigeminal nucleus - VI abducens nucleus - VII facial nucleus - Xd dorsal vagal nucleus - XII hypoglossal nucleus     

大鼠中缝大核突触囊泡在电针后的变化及其图象分析

应用透射电镜和图象分析方法,对电针后大鼠中缝大核突触前终扣内突触囊泡的数量以及突触前终扣内容物的量的变化进行了研究。结果表明:电针后,中缝大核突触前终扣内圆形清亮囊泡和颗粒囊泡的数量明显减少,突触囊泡聚集并向突触活性带集中。图象分析结果:电针后,突触前终扣内容物的量较对照组明显减少,而且内容物分布不均匀并在突触膜附近集中。本实验为针刺镇痛的理论研究提供了形态学依据。     

Properties of ipsilateral retinogeniculate afferents in albino and hooded rats

By recording single unit activities from the dorsal lateral geniculate nucleus in albino and hooded rats, physiological properties of the ipsilateral retinogeniculate afferents were compared with those of the contralateral ones. The results show that the ipsilateral retinogeniculate pathway was characterized by intermediate conduction velocities, relatively high incidence of the tonic response and the visual field representation of central 30° from the vertical midline on both sides.     

Repeated Baclofen treatment ameliorates motor dysfunction,suppresses reflex activity and decreases the expression of signaling proteins in reticular nuclei and lumbar motoneurons after spinal trauma in rats

The interruption of supraspinal input to the spinal cord leads to motor dysfunction and the development of spasticity. Clinical studies have shown that Baclofen (a GABA_B agonist), while effective in modulating spasticity is associated with side-effects and the development of tolerance. The aim of the present study was to assess if discontinued Baclofen treatment and its repeated application leads antispasticity effects, and whether such changes affect neuronal nitric oxide synthase (nNOS) in the brainstem, nNOS and parvalbumin (PV) in lumbar α-motoneurons and glial fibrillary acidic protein in the ventral horn of the spinal cord. Adult male Wistar rats were exposed to Th9 spinal cord transection. Baclofen (30 mg/b.w.) diluted in drinking water, was administered for 6 days, starting at week 1 after injury and then repeated till week 4 after injury. The behavior of the animals was tested (tail-flick test, BBB locomotor score) from 1 to 8 weeks. Our results clearly indicate the role of nitric oxide, produced by nNOS in the initiation and the maintenance of spasticity states 1, 6 and 8 weeks after spinal trauma. A considerable decrease of nNOS staining after Baclofen treatment correlates with improvement of motor dysfunction. The findings also show that parvalbumin and astrocytes participate in the regulation of ion concentrations in the sub-acute phase after the injury.     

Role of glutamatergic receptors located in the nucleus raphe magnus on antinociceptive effect of morphine microinjected into the nucleus cuneiformis of rat

Neurons in the nucleus cuneiformis (CnF), located just ventrolateral to the periaqueductal gray, project to medullary nucleus raphe magnus (NRM), which is a key medullary relay for descending pain modulation and is critically involved in opioid-induced analgesia. Previous studies have shown that antinociceptive response of CnF-microinjected morphine can be modulated by the specific subtypes of glutamatergic receptors within the CnF. In this study, we evaluated the role of NMDA and kainate/AMPA receptors that are widely distributed within the NRM on morphine-induced antinociception elicited from the CnF. Hundred and five male Wistar rats weighing 250-300 g were used. Morphine (10, 20 and 40 microg) and NMDA receptor antagonist, MK-801 (10 microg) or kainate/AMPA receptor antagonist, DNQX (0.5 microg) in 0.5 microl saline were stereotaxically microinjected into the CnF and NRM, respectively. The latency of tail-flick response was measured at set intervals (2, 7, 12, 17, 22, 27 min after microinjection) by using an automated tail-flick analgesiometer. The results showed that morphine microinjection into the CnF dose-dependently causes increase in tail-flick latency (TFL). MK-801 microinjected into the NRM, just 1 min before morphine injection into the CnF, significantly attenuated antinociceptive effects of morphine. On the other hand, DNQX microinjected into the NRM, significantly increased TFL after local application of morphine into the CnF. We suggest that morphine related antinociceptive effect elicited from the CnF is mediated, in part, by NMDA receptor at the level of the NRM whereas kainite/AMPA receptor has a net inhibitory influence at the same pathway.