Splenic, renal, and cardiac nerves have unequal dependence upon tonic supraspinal inputs

Meckler, R. L.; Weaver, Lynne C.

doi:10.1016/0006-8993(85)90254-9

Cited by 50 publications

(20 citation statements)

References 26 publications

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“…The discharge rate of the renal units that continued to fire after severing the spinal cord was not different from their discharge rate in the intact state, indicating that the profound decrease in multifibre renal nerve activity following spinal cord transection was due to the cessation of activity of a subpopulation of renal neurones, rather than a general decrease in the spontaneous discharge of all neurones. These results, and those of other studies (Ninomiya & Irisawa, 1975;Meckler & Weaver, 1985;Meckler & Weaver, 1987), suggest that ongoing sympathetic outflow directed to the splanchnic capacitive circulation is less dependent upon supraspinal drive than is that directed to the kidney.…”

Section: Discussionsupporting

confidence: 74%

“…Systemic arterial pressure was monitored using Gould-Statham P-23 ID transducers, displayed on a Grass polygraph, and recorded on electromagnetic tape. In thirteen cats pressoreceptor-sensitive multifibre activity of mesenteric and renal nerves was simultaneously recorded, using standard electrophysiological techniques (Meckler & Weaver, 1985). All neural activity was monitored on oscilloscopes and recorded on electromagnetic tape.…”

Section: Methodsmentioning

confidence: 99%

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Multi‐ and single‐fibre mesenteric and renal sympathetic responses to chemical stimulation of intestinal receptors in cats.

Stein

Weaver

1988

The Journal of Physiology

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SUMMARY1. In cats anaesthetized with a-chloralose and artificially respired, stimulation of intestinal receptors with bradykinin caused greater reflex excitation of mesenteric than of renal efferent multifibre nerve activity and significant pressor responses.2. Activity of all nerve bundles used in this study was inhibited by stimulation of pressoreceptors. Increases in systemic arterial pressure caused inhibition of activity of renal nerves which was significantly greater than that of mesenteric nerves.3. Spinal transection caused significant decreases in tonic renal nerve activity without altering the ongoing discharge rate of mesenteric nerves. Stimulation of intestinal receptors in spinal cats still caused significant increases in discharge of mesenteric and renal nerves, indicating that this reflex contains a spinal component.4. Recordings of activity of individual fibres within mesenteric (21) and renal (23) nerves provided information regarding the basis for the multifibre responses to stimulation of intestinal receptors. The same proportion of fibres from both nerves was excited, but the increase in activity of mesenteric fibres was significantly greater than that of renal fibres.5. Mesenteric fibres could be classified into two groups, based on their sensitivity to pressoreceptor influences. Fibres that exhibited pressoreceptor-independent discharge had the greatest responses to stimulation of intestinal receptors.6. Following spinal transection the majority of mesenteric fibres continued to fire, whereas most renal fibres became quiescent.7. The non-uniform pattern of neuronal excitation to chemical stimulation of intestinal receptors was manifest after spinal transection, demonstrating that exclusively spinal pathways can mediate this differential response pattern.8. These results support the hypothesis that viscero-sympathetic reflexes may be organized to cause preferential excitation of neural activity directed to the organ from which the reflex originates.

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Section: Discussionsupporting

confidence: 74%

Section: Methodsmentioning

confidence: 99%

Multi‐ and single‐fibre mesenteric and renal sympathetic responses to chemical stimulation of intestinal receptors in cats.

Stein

Weaver

1988

The Journal of Physiology

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“…Many renal and splenic units discharged in the expiratory phase of the respiratory cycle, perhaps due to influences of vagal afferent fibres in these artificially respired animals (Cohen, Gootman & Feldman, 1980). In general, the higher proportion of renal than splenic fibres with ongoing discharge related to respiratory or cardiac cycles parallels differences in dependence of renal and splenic nerve discharge on supraspinal sources of tonic excitatory drive (Meckler & Weaver, 1985). Indeed, firing of more than half of the renal fibres ceased, whereas 78 % of the splenic fibres continued to fire after spinal cord transection.…”

Section: Discussionmentioning

confidence: 93%

Characteristics of ongoing and reflex discharge of single splenic and renal sympathetic postganglionic fibres in cats.

Meckler

Weaver

1988

The Journal of Physiology

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SUMMARY1. Electrical discharge of thirty-nine single splenic and renal postganglionic nerve fibres was recorded in artificially respired, chloralose-anaesthetized cats.2. Ongoing discharge rates, averaged over 10 s periods, did not differ between renal and splenic fibres. All neurones of both groups had irregular discharge frequencies.3. Half of the splenic population and all renal fibres had cardiac-related discharge patterns. Of those tested for respiratory-related firing, 30 % of the splenic fibres and 69% of the renal fibres exhibited this pattern.4. Firing of splenic fibres was less inhibited than that of renal fibres by stimulation of pressoreceptors with phenylephrine-induced increases in blood pressure. Firing of splenic fibres also was less excited than that of renal fibres by unloading pressoreceptors with depressor doses of sodium nitroprusside.5. Chemical stimulation of splenic afferent nerves with bradykinin consistently elicited greater increases in splenic than renal nerve discharge by causing large increases in firing of all splenic fibres and smaller excitatory responses in 75 % of the renal fibres.6. Application of bradykinin to the intestinal serosa produced greater increases in renal than splenic nerve discharge by consistently causing increased firing of renal fibres and by causing excitation, inhibition, or no change in splenic fibre discharge.7. Responses of splenic and renal fibres to stimulation of splenic and intestinal afferent nerves after spinal cord transection were similar to those responses elicited when the neuraxis was intact.8. In conclusion, the differerntial reflex responses of splenic and renal neuronal populations can be due to the heterogeneity or to the intensity of responses within a neuronal population.

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“…Urapidil differed from these four drugs in that it caused a uniform reduction in sympathetic nerve activity at all the levels being recorded. These observations combined with the large amount of evidence that descending projections can selectively influence certain sympathetic outflows (Futuro-Neto & Coote, 1982b;Barman et al, 1984;Meckler & Weaver, 1985;Stein et al, 1989) suggest that such patterning may be dependent on the chemical transmitter that is released by a particular descending pathway. 5-HT-containing neurones, which are found in the raphe and the ventrolateral medulla, have been shown to project to preganglionic sympathetic motoneurones in the intermediolateral cell column (Bowker et al, 1981;Loewy & Neil, 1981;Jacobs et al, 1984;Marson & Loewy 1985;Ciriello et al, 1986;1988).…”

Section: Resultsmentioning

confidence: 99%

Evidence that different regional sympathetic outflows vary in their sensitivity to the sympathoinhibitory actions of putative 5‐HT_1A and α₂‐adrenoceptor agonists in anaesthetized cats

Ramage

Wilkinson

1989

British J Pharmacology

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1 An investigation was carried out to determine whether the centrally acting hypotensive drugs whose mechanisms of action are due either to activation of 5-HTIA receptors (flesinoxan, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and urapidil also an a,-adrenoceptor antagonist) or to activation of M2-adrenoceptors (clonidine and moxonidine) cause differential sympathoinhibition. 2 Cats were anaesthetized with a-chloralose and simultaneous recordings were made of whole cardiac, splanchnic and renal nerve activity, blood pressure and heart rate. Cumulative doseresponse (i.v.) curves were constructed in separate experiments for the above hypotensive agents on these parameters. 3 Renal nerve activity was found to be more sensitive to the sympathoinhibitory action of flesinoxan and 8-OH-DPAT when compared with cardiac nerve activity, whereas the reverse was observed for clonidine and moxonidine, cardiac being more sensitive than renal nerve activity. Splanchnic nerve activity was similarly affected by all drugs. Furthermore at the highest dose, all drugs tended to cause complete inhibition in all regional sympathetic nerve outflows. 4 Urapidil differed from all the above hypotensive drugs in that it caused a similar degree of sympathoinhibition in all sympathetic outflows at all doses. It is suggested that this may be due to the ability of urapidil to block central a,-adrenoceptors in addition to stimulation of 5-HTlA receptors. IntroductionThere is a large amount of evidence to suggest that 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and flesinoxan activate 5-HTlA receptors to cause their hypotensive action McCall et al., 1987;Ramage & Fozard, 1987;Doods et al., 1988;Wouters et al., 1988;Laubie et al., 1989) and that such an action is entirely within the central nervous system. However, only moderate thoracic preganglionic sympathoinhibition is observed in anaesthetized cats (Ramage & Fozard, 1987;Ramage et al., 1988). One explanation for this lack of correlation between the thoracic sympathoinhibitory action and the hypotensive action of 8-OH-DPAT and flesinoxan is that these drugs could be having a more potent sympathoinhibitory action at a different level or levels of sympathetic outflow. In this respect the sympathoinhibitory action of flesinoxan on renal ' Author for correspondence.outflow, when compared with other sympathetic outflows has been shown to be greater (Ramage et al., 1988). However a weakness of this latter investigation was that the recordings made from different sympathetic outflows were carried out in separate animals and further, that some of the outflows were recorded from preganglionic, while others were recorded from postganglionic nerves. In order to overcome these weaknesses the present experiments were carried out in which the sympathoinhibitory actions of flesinoxan and 8-OH-DPAT were studied on cardiac, splanchnic and renal nerve activity recorded simultaneously in the same animal. Further, the effects of other hypotensive agents, urapidil (which has also been shown to bind...

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Splenic, renal, and cardiac nerves have unequal dependence upon tonic supraspinal inputs

Cited by 50 publications

References 26 publications

Multi‐ and single‐fibre mesenteric and renal sympathetic responses to chemical stimulation of intestinal receptors in cats.

Multi‐ and single‐fibre mesenteric and renal sympathetic responses to chemical stimulation of intestinal receptors in cats.

Characteristics of ongoing and reflex discharge of single splenic and renal sympathetic postganglionic fibres in cats.

Evidence that different regional sympathetic outflows vary in their sensitivity to the sympathoinhibitory actions of putative 5‐HT_1A and α₂‐adrenoceptor agonists in anaesthetized cats

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Splenic, renal, and cardiac nerves have unequal dependence upon tonic supraspinal inputs

Cited by 50 publications

References 26 publications

Multi‐ and single‐fibre mesenteric and renal sympathetic responses to chemical stimulation of intestinal receptors in cats.

Multi‐ and single‐fibre mesenteric and renal sympathetic responses to chemical stimulation of intestinal receptors in cats.

Characteristics of ongoing and reflex discharge of single splenic and renal sympathetic postganglionic fibres in cats.

Evidence that different regional sympathetic outflows vary in their sensitivity to the sympathoinhibitory actions of putative 5‐HT1A and α2‐adrenoceptor agonists in anaesthetized cats

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Evidence that different regional sympathetic outflows vary in their sensitivity to the sympathoinhibitory actions of putative 5‐HT_1A and α₂‐adrenoceptor agonists in anaesthetized cats