大鼠延髓腹面降压区微量注射L—精氨酸对心血管活动的影响

目的：观察NO前体L－精氨酸（L－Arg)微量注入大鼠延髓腹面降压区（VSMd）对心血管活动的影响及其和L－谷氨酸（L－Glu)降压作用的关系。方法：采用延髓腹外侧部微量注射法,以整体灌流肾为模型观察与NO有关的药物对心血管活动的影响。结果：①VSMd内微量注入L－Arg,动脉血压（AP）呈剂量依赖性升高,肾灌流压（PPK）与AP同步上升,与注入生理盐水对照,差异均具有显著意义,但L－Arg对心率无显著影响;②预先在VSMd内注入甲基蓝可取消L－Arg的升压、升PPK作用;③VSMd内注入L－Glu,AP下降。如预先注入L－Arg后5min再注入L－Glu,L-Glu的降压效应被衰减,其衰减程度依赖于L－Arg剂量。结论：VSMd的L－Arg-NO通路参与延髓心血管中枢对AP的调控,其机制之一可能是通过cGMP抑制VSMd内的谷氨酸能神经突触。     

Neurokinin-1 receptor-expressing cells regulate depressor region of rat ventrolateral medulla

Intraparenchymal injection of the saporin conjugate [Sar9, Met (O2)11] substance P-saporin (SSP-SAP) into the ventrolateral medulla (VLM) destroys neurokinin-1 receptor-immunoreactivity (NK1R-ir) neurons selectively. This treatment attenuates the hypotension caused by injection of DL-homocysteic acid (DLH) into the caudal VLM (CVLM). Here we ask whether SSP-SAP creates this deficit by destroying the CVLM GABAergic interneurons that mediate the sympathetic baroreflex (baroactivated depressor neurons) or by destroying other VLM neurons. Two weeks after unilateral SSP-SAP treatment (97% loss of VLM NK1R-ir neurons) DLH-induced hypotension and sympathetic tone inhibition were blunted on the lesioned side. Unlesioned or unilaterally lesioned rats received phenylephrine (PE) while awake to identify CVLM baroactivated depressor neurons by the presence of Fos-ir nuclei. Although CVLM Fos-ir cells were not NK1R-ir, their number was reduced approximately 60-70% on the SSP-SAP-injected side. SSP-SAP spared VLM neurons devoid of NK1R-ir, such as the catecholaminergic cells and the precerebellar glutamatergic neurons. In the pre-B?tzinger region of the VLM the toxin killed glutamatergic neurons while sparing glycinergic and GABAergic inhibitory neurons. In the CVLM region approximately 26% of the inhibitory cells were destroyed. In conclusion, the baroactivated depressor neurons of the CVLM do not appear to express NK1Rs but their activity is probably modulated by a population of excitatory NK1R-ir cells located in the VLM. The results also suggest that a region located below the CVLM (subCVLM) may contain an unrelated population of GABAergic depressor neurons that are NK1R-ir but are either not barosensitive or do not express Fos during baroreceptor stimulation.     

The effect of the lateral reticular nucleus of the medulla oblongata on the cerebellar cortex

It was established as a result of a laminar analysis of evoked potentials (EP) in the paramedian lobe of the cerebellum of unanesthetized cats that in response to stimulation of the lateral reticular nucleus (LRN) excitation of granulosa cells develops which is not accompanied by excitation of Purkinje cells. Destruction of the lateral nucleus leads to a considerable decrease in the "diffuse" component of the EP which develop during stimulation of the somatic nerves. The results obtained show that the afferent pathway whose fibers innervate granulosa cells of a special type, which have been previously described, passes through the LRN. These cells have extensive receptive fields and do not directly affect the activity of Purkinje cells. A hypothesis is proposed on the basis of the results obtained and data in the literature that the extensive receptive fields of the LRN cells and of the granulosa cells innervated by them are due to interneuronal connections within the lateral nucleus.Institute of Problems of Information Transmission, Academy of Sciences of the USSR, Moscow. Laboratory on the Use of Mathematical Methods in Biology, Moscow University. Translated from Neirofiziologiya, Vol. 2, No. 6, pp. 581–586, November–December, 1970.     

Immunohistochemical mapping of adrenomedullin in the human medulla oblongata

We studied by immunocytochemistry the expression of adrenomedullin (AM) in the human medulla oblongata, sampled from 13 adult subjects (mean age: 38 years), whose medical history was negative for neurological and neurovascular pathologies. Immunoreactive neurons were found in the medulla oblongata with statistically significant differences among the various nuclei (one-way ANOVA, P < 0.001). The hypoglossal nucleus showed higher AM expression than that of the spinal tract of the trigeminal nerve (P < 0.05), solitary tract nucleus (P < 0.05), nucleus intercalatus (P < 0.05), and area postrema (P < 0.05). The arcuate nucleus and inferior olivary nuclear complex showed lower AM expression than the hypoglossal nucleus (P < 0.001), vestibular nuclei (P < 0.01), cuneate and gracile nuclei (P < 0.05), lateral column of the reticular formation (P < 0.05), and nucleus ambiguous (P < 0.05). Furthermore the nuclei were grouped with reference to their function, into somatic sensitive nuclei, somatic motor nuclei, visceral nuclei, reticular formation, and nuclei involved in cerebellar functions. The ANOVA revealed statistically significant differences (P < 0.001) in mean AM scores among the different groups. Nuclei involved in cerebellar function showed the lowest mean AM score (P < 0.05). The difference in AM score between somatic motor nuclei and visceral nuclei was also statistically significant (P < 0.05). Widespread AM immunoreactivity in the nuclei of the medulla oblongata may account for the role of the peptide in neuronal function and regulation of regional blood flow. Differences in the expression of AM in the nuclei studied indicate the different involvement of AM in neurotransmission and neuromodulation.     

Development of catecholaminergic neurons in the human medulla oblongata

Distribution and maturation of catecholaminergic (CA) neurons have been studied by tyrosine hydroxylase immunohistochemistry in the medulla oblongata of human fetuses aged 14.5-25 weeks of gestation. Already at 14.5 weeks, CA neurons were observed in two longitudinally oriented cell clusters, one located ventrolaterally in the area of the lateral reticular and ambiguous nuclei, the other one dorsomedially forming 4 groups related to the dorsal vagal nucleus, the commissural nucleus of the vagus, the nucleus of the tractus solitarius and the area postrema. CA neurons in the area postrema were often found close to blood vessels. Scattered intermediate CA neurons were seen between these two larger clusters. CA neurons still appeared immature exhibiting bipolar morphology with only one or two short stout processes, which hardly branched. At 21 weeks, CA neurons occupied essentially the same location, but had a more mature morphology. Though still bipolar in shape, they had thinner and much longer processes which frequently branched. Both in the ventrolateral and the dorsomedial cell clusters, these processes were frequently lying close to blood vessels. At 25 weeks, CA cells had matured into multipolar neurons with long thin processes forming fine fiber networks in the ventrolateral medulla as well as around and within the dorsal vagal and solitarius nuclei. Only at this stage, a distinct CA fiber tract was seen located in the region of the tractus solitarius. Our results indicate that CA neurons in the human medulla, which are presumably involved in the control of ventilation and blood pressure, though generated rather early during development, mature relatively late.     

Electrical activity of the sympathetic ganglia during the depressor reflex

Tonic activity of neurons of the superior cervical sympathetic ganglion was recorded by the "sucrose gap" method and in the 4th and 5th lumbar sympathetic ganglia with the aid of focal nonpolarizing electrodes in acute experiments on anesthetized cats and rabbits. The preganglionic fibers of the ganglia were left intact. Stimulation of the depressor nerve not only sharply inhibited the tonic activity of the ganglia but also led to the appearance of electropositive potentials of 0.7 ± 0.2 mV in the superior cervical ganglion and 20–250 µV in the lumbar ganglia. The amplitude of this potential was unchanged by atropine (1 · 10^–6M). A similar effect occured without stimulation of the depressor nerve, after division of the preganglionic fibers or blocking of their conduction; it is attributed to the cessation of preganglionic tonic impulses which induce not only spikes, but also many EPSPs in neurons of the ganglion. Their frequency in the lumbar ganglia was 4/sec. Summation of these EPSPs leads to constant electronegativity of the ganglion surface relative to the postganglionic fibers, and its disappearance is recorded as a positive potential. Stimulation of the depressor nerve thus does not induce IPSPs in the ganglion; consequently, the inhibition of synaptic activity observed under these circumstances is located in the CNS and not in the ganglion.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 6, No. 5, pp. 519–524, September–October, 1974.