Journal of the autonomic nervous system
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J. Auton. Nerv. Syst. · Feb 1989
Dermorphin inhibits micturition reflex in rats at a central site of action.
Intrathecal dermorphin (0.8-80 ng) or [D-Ala2, D-Leu5]-enkephalin (DADLE, 5.7-171 ng) produced a dose-related marked inhibition of reflex micturition in urethane-anesthetized rats until voiding was suppressed and overflow incontinence ensued. These effects of dermorphin or DADLE were promptly abolished by i.v. naloxone (0.2 mg/kg). The inhibitory effect of dermorphin but not that of DADLE was partially prevented by systemic capsaicin desensitization (50 mg/kg s.c., 4 days before). Intravenous dermorphin had little or no effect on micturition up to 8 micrograms/kg.
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J. Auton. Nerv. Syst. · Mar 1988
Immunohistochemical localisation and electrophysiological actions of GABA in prevertebral ganglia in guinea-pig.
Immunohistochemical techniques were used to detect the presence of a GABA-like material in prevertebral sympathetic ganglia in guinea-pigs. Varicose, immunolabelled nerve fibres were observed in close proximity to sympathetic neurones in inferior mesenteric ganglia and coeliac ganglia. Non-varicose, immunolabelled nerve fibres were observed in lumbar colonic nerves and superior coeliac nerves, i.e. in nerve bundles peripheral to prevertebral ganglia. ⋯ The reversal potential of the GABA-induced slow depolarisation was -37 mV, a value close to the chloride equilibrium potential for sympathetic neurones. The actions of GABA were reversibly reduced by the GABAA antagonist, bicuculline, and were modulated in a predictable manner by substituting chloride ions with methane-sulphonate ions. These results indicated that GABA, and presumably GABAergic nerves in prevertebral ganglia, modulate the excitability of sympathetic neurones by acting on GABAA receptors linked to a chloride ionophore.
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J. Auton. Nerv. Syst. · Aug 1987
Comparative StudyOxytocin administered intrathecally preferentially increases heart rate rather than arterial pressure in the rat.
Oxytocin was administered intrathecally at a dose of 6.5 nmol to the 9th or 2nd thoracic level of the spinal cord in the rat. This increased heart rate but had no effect on arterial pressure. The increase in heart rate began within 1 and 5 min and reached a peak at 10-30 min; the maximum increase, at 10 min after administration, at the second thoracic level was 65.4 +/- 13.8 (S. ⋯ It is concluded that the intrathecal administration of reached a maximum of 0.6% of the total injected by 30 min after administration. It is concluded that the intrathecal administration of oxytocin increases heart rate via an action in the spinal cord, presumably on sympathetic preganglionic neurons. Our results are consistent with earlier suggestions that oxytocin may be a chemical mediator of synaptic transmission onto sympathetic preganglionic neurons.
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J. Auton. Nerv. Syst. · Mar 1986
Properties of femoral venous afferent inputs and lumbosacral distribution of spinal evoked activity.
The present studies were done to determine details of the anatomical and physiological characteristics of femoral-saphenous venous afferent input to the lumbar spinal cord. Gross anatomical examination revealed that afferent bundles could be seen coursing from the saphenous nerve to the femoral-saphenous vein. Compound action potentials elicited by femoral-saphenous venous afferent stimulation were recorded from the femoral nerve and in dorsal rootlets of the 6th lumbar cord segment. ⋯ L6 was also the cord segment from which the largest amplitude cord dorsum negative potentials were recorded, while action potentials with large late positive waves were recorded from more caudal cord segments. These observations suggested that the L6 segment contained the largest number of spinal neurons responding to primary femoral-saphenous venous afferent input, and that input reached the more caudal segments via intersegmental connections. A proposed physiological role of these afferents is briefly described.
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J. Auton. Nerv. Syst. · Jul 1985
An intracellular study of the synaptic input to sympathetic preganglionic neurones of the third thoracic segment of the cat.
In chloralose anaesthetized, paralyzed and artificially ventilated cats intracellular recordings were obtained from sympathetic preganglionic neurones (SPN) of the third thoracic segment of the spinal cord identified by antidromic stimulation of the white ramus T3. The synaptic input to SPNs was assessed, in cats with intact neuraxis or spinalized at C3, by electrical stimulation of segmental afferent fibres in intercostal nerves and white rami of adjacent thoracic segments and by stimulation of the ipsi- and contralateral dorsolateral funiculus and of the dorsal root entry zone of the cervical spinal cord. In both preparations SPNs showed on-going synaptic activity which predominantly consisted of excitatory post-synaptic potentials (EPSPs). ⋯ EPSPs of these various groups were elicited in a varying percentage in SPNs. EPSPs of the most rapidly conducting pathway were subthreshold for the generation of action potentials; some EPSPs of this group had a constant latency suggesting a monosynaptic pathway to SPNs. Stimulation of the dorsal root entry zone at the cervical level yielded essentially the same results as stimulation of the dorsolateral funiculus.(ABSTRACT TRUNCATED AT 400 WORDS)