Intermediolateral Column Of Spinal Cord Research Articles

Pre and postganglionic innervation of rat adrenal gland by fluorescent tract tracer – Fast blue

IntroductionTo search for pre and postganglionic neurons innervating the adrenal gland by injecting retrograde tract tracer fast blue in the adrenal medulla. MethodsThe motor innervation of rat adrenal gland was studied by a fluorescent tract tracer fast blue. 5 μl of 2% aqueous suspension of fast blue was injected into left adrenal gland. After a survival period of 4–5 days, spinal cord, sympathetic ganglia, suprarenal ganglion, coeliac ganglion and left adrenal gland were dissected out and 15 μm thick plastic sections (JB4 Polysciences) were examined under a fluorescent microscope. ResultsRetrogradely labeled preganglionic neurons were observed in the ipsilateral intermediolateral column of spinal cord from T3 to L2 spinal segments with maximum concentration of labeled neurons from T6 to T11. The labeled neurons were multipolar, spherical or fusiform in shape with transverse diameter 10–20 μm and vertical diameter varying from 12 to 30 μm. Postganglionic labeled neurons were also observed in the left suprarenal ganglion and left sympathetic ganglia (T5 –L2) with maximum concentration from T6 to L1. Labeled neurons varied from 12 to 30 μm in diameter and were randomly distributed throughout the ganglion. DiscussionThe preganglionic neurons from T3 to L2 spinal segments and postganglionic nerve fibers from ipsilateral sympathetic ganglia (T5 –L2) and suprarenal ganglion supplying the adrenal gland might be responsible for the hormone release by regulating blood flow and also by directly innervating the parenchymal cells.

Different sub‐populations of pre‐sympathetic neurons are revelead by acute hypoxia in brainstem slices of adult rats (710.7)

In this study we evaluated, in brainstem slices from adult rats, the effects of acute hypoxia (AH) on the firing rate of pre‐sympathetic neurons in rostral ventrolateral medulla sending projections to the intermediolateral column of spinal cord (RVLM‐IML neurons). Anesthetized male Wistar rats (PO 30) were submitted to microinjection of fluorescent retrograde tracer into the spinal cord (T3‐T5) to label the RVLM‐IML neurons. Five days later the rats were anesthetized to obtain brainstem coronal slices. The RVLM‐IML neurons were recorded using whole‐cell patch‐clamp and the firing rate was analyzed before and after perfusion of slice to AH for 2 minutes with hypoxic solution (95% N2 and 5% CO2) in the presence of synaptic blockers. After the AH protocol the viability of RVLM‐IML neurons were verified by the perfusion with normal solution (95% O2 and 5% CO2). All recorded RVLM‐IML neuronsof adult rats (n=17) presented intrinsic spontaneous firing activity. Three sub‐populations of RVLM‐IML neurons were identified after AH exposure: a) 3 neurons decreased their firing rate after AH(‐ 34,10%, p= 0,0225); b) 4 neurons increased their firing rate after AH (+ 40,86%, p= 0,0249) and c) 10 neurons were not affected by AH(± 3,54%, p= 0,5380. Hypoxia produced no changes in input resistance and resting membrane potential in these neurons. The data show that pre‐sympathetic neurons in the brainstem slices of adult rats present pacemaker activity and different sub‐populations of pre‐sympathetic neurons are revealed in response to AH.Grant Funding Source: Supported by FAPESP and CNPQ

Heart failure‐induced changes in rostral ventral lateral medulla neurotransmitter receptor mRNA expression

Activation of the sympathetic nervous system occurs in heart failure (HF) and in response to acute bouts of hyperthermia. However, our previous work has demonstrated that rats with HF display attenuated sympathetic nerve discharge (SND) responses to an acute bout of hyperthermia and that SND responses to hyperthermia are mediated via brainstem neural circuits. Despite this, HF-induced changes in excitatory (NMDA) and inhibitory (GABA) neurotransmitter systems within brainstem nuclei are not well understood. The rostral ventral lateral medulla (RVLM) has substantial sympathetic efferent projections to the intermediolateral column of spinal cord. Thus, we hypothesized that the RVLM of rats with HF may be characterized by altered expression of NMDA and GABAA receptor subunits. Using real-time PCR analysis we compared NMDA and GABAA receptor subunit expression in the RVLM of sham-operated and HF rats. Results of these preliminary studies indicate that in rats with HF mRNA expression of NMDA receptor subunits NR1, NR2A, and NR2B are increased between two and ten fold, whereas GABAA receptor subunits are increased two-fold or less. These results suggest that although basal levels of GABAA receptor mRNA are only slightly elevated in rats with HF, expression of excitatory neurotransmitter receptor subunits in the RVLM are significantly increased. Neurotransmitter receptor subunit expression following an acute bout of hyperthermia continues to be determined, however, we hypothesize that GABAA and NMDA receptor subunit expression will be increased and decreased respectively in rats with HF, thereby contributing to the inability of HF rats to increase SND in response to a thermal challenge. Supported by NIH HL-65346 and HL-69755 (MJK) and AHA Postdoctoral Grant 0520105Z (BGH).

Identification of NPY-induced c-Fos expression in hypothalamic neurones projecting to the dorsal vagal complex and the lower thoracic spinal cord.

Neuropeptide Y exerts profound effects on body weight and glucose homeostasis. We have investigated the effect of centrally administered neuropeptide Y on the activity of descending neurones of the hypothalamic paraventricular nucleus by combining retrograde tract tracing with c-Fos immunocytochemistry. Male rats were injected with True Blue into the dorsal vagal complex and with FluoroGold into the intermediolateral column of the lower thoracic spinal cord. One week after the last surgical procedure, animals were injected centrally with an orexigenic dose of neuropeptide Y (5 microg) and sacrificed 60 to 240 minutes following this injection. Temporal analysis of NPY-induced c-Fos expression showed a peak at 90 minutes, which was nearly returned to basal levels between 120 and 240 minutes. Expression of c-Fos was prominent in several of the subnuclei of the paraventricular nucleus and in the adjacent perifornical nucleus. Neurones projecting to the spinal cord were prominent in the dorsal, lateral, and ventral portion of the medial parvicellular subnuclei of the PVN. About 15% of IML projecting neurones of the medial parvicellular subnucleus were Fos-positive, whereas less than 5% of IML projecting neurones from other subnuclei were Fos-positive. Hardly any PVN neurones projecting to the dorsal vagal complex were concomitantly Fos-positive. A considerably larger (>10%) proportion of perifornical neurones projecting to the nucleus of the solitary tract were c-Fos-immunopositive. In conclusion, NPY induces c-Fos in paraventricular neurones projecting to intermediolateral column of the spinal cord and in neurones of the perifornical nucleus projecting to the dorsal vagal complex.

Nitric oxide-synthesizing neurons originating at several different levels innervate rat penis

While the crucial role of neurally produced nitric oxide in mediating penile erection is well established, the understanding of the peripheral neuroanatomy of the nitric oxide-ergic pathways is still incomplete. This study was designed to elucidate further the distribution of nitric oxide synthase, and its relation to the distribution of neuropeptides and tyrosine hydroxylase in all penis-projecting neural pathways. A triple-labelling technique was employed, with the retrograde tracer Fluoro Gold combined with neuropeptide immunohistochemistry and nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase histochemistry, a marker of nitric oxide synthase. The presence within the penis of scattered nerve cell bodies exhibiting NADPH-diaphorase activity was revealed. Most (76%) of the penis-projecting neurons in the major pelvic ganglion exhibited NADPH-diaphorase activity and immunoreactivity to vasoactive intestinal peptide, while none of them contained tyrosine hydroxylase. Sympathetic paravertebral postganglionic neurons, in turn, contained tyrosine hydroxylase, but did not exhibit NADPH-diaphorase activity. In the afferent, sensory neurons projecting to the penis from the dorsal root ganglia, NADPH-diaphorase activity coexisted with immunoreactivity to both substance P (8%) and calcitonin gene-related peptide (26%). Preganglionic neurons originating in the spinal cord intermediolateral column at the thoracolumbar level T11-L3 terminated, not only in the major pelvic ganglion, but also within the penis. The majority (81%) of the penis-projecting neurons exhibited NADPH-diaphorase activity. The results indicate that the rat penis receives several different nitric oxide-ergic neural projections. It is therefore possible that nitric oxide affects penile erection at several neuronal levels.