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Biomedical subjects

J Donnerer

Publications and source records attributed to J Donnerer.

At least 37 records · Page 2Linked to original sources
PubMed1995

Neuroantibodies: ectopic expression of a recombinant anti-substance P antibody in the central nervous system of transgenic mice.

Recombinant antibodies are efficiently secreted by cells of the nervous system. Thus, their local expression in the CNS of transgenic mice could be used to perturb the function of the corresponding antigen. As a first application of this approach, we have generated transgenic mice that express antibodies against the neuropeptide substance P, under the transcriptional control of the promoter of the neuronal gene vgf. The transgenic antibodies are expressed in a tissue-specific and developmentally regulated manner and are effective in competing with the endogenous substance P, as demonstrated by a marked inhibition of neurogenic inflammation and by motor deficits. This phenotypic knockout approach may provide a complementary alternative to gene knockout by homologous recombination.

Animals↗
PubMed1994

Human and rat primary C-fibre afferents store and release secretoneurin, a novel neuropeptide.

Secretoneurin is a recently discovered neuropeptide derived from secretogranin II (SgII). Since this peptide could be detected in the dorsal horn of the spinal cord we studied whether it is localized in and released from primary afferent neurons. Secretoneurin was investigated with immunocytochemistry and radioimmunoassay in spinal cord, dorsal root ganglia and peripheral organs. SgII mRNA was determined in dorsal root ganglia. Normal rats and rats pre-treated neonatally with capsaicin to destroy selectively polymodal nociceptive (C-) fibres were used. Slices of dorsal spinal cord were perfused in vitro for release experiments. Immunocytochemistry showed a distinct distribution of secretoneurin-immunoreactivity (IR) in the spinal cord and, lower brainstem. A particularly high density of fibres was found in lamina I and outer lamina II of the caudal trigeminal nucleus and of the spinal cord. This distribution was qualitatively identical in rat and human post-mortem tissue. Numerous small diameter and some large dorsal root ganglia neurons were found to contain SgII mRNA. Capsaicin treatment led to a marked depletion of secretoneurin-IR in the substantia gelatinosa, but not in other immunopositive areas of the spinal cord and to a substantial loss of small (< 25 microns) SgII-mRNA-containing dorsal root ganglia neurons. Radioimmunoassay revealed a significant decrease of secretoneurin-IR in the dorsal spinal cord, the trachea, heart and urinary bladder of capsaicin-treated rats. Perfusion of spinal cord slices with capsaicin as well as with 60 mM potassium led to a release of secretoneurin-IR. In conclusion, secretoneurin is a neuropeptide which is stored in and released from capsaicin-sensitive, primary afferent (C-fibre) neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Neonatal capsaicin treatment does not prevent splanchnic vasodilatation in portal-hypertensive rats.

It has been suggested that the peripheral sensory neurons are involved in the splanchnic hemodynamic changes of portal hypertension. Therefore the influence of permanent ablation of sensory neurons by neonatal capsaicin pretreatment (50 mg/kg, subcutaneously) on the development of the hyperdynamic splanchnic circulation in portal-hypertensive rats was studied. In adulthood, portal hypertension was induced with partial portal vein ligation. In study 1, systemic and splanchnic hemodynamics were measured by means of a radiolabeled-microsphere technique in portal-hypertensive rats, under ketamine anesthesia, pretreated with capsaicin or vehicle. Mean arterial pressure, heart rate, cardiac index, systemic and splanchnic vascular resistance, portal pressure, portal venous inflow, portal-collateral resistance and portal-systemic shunting were not significantly different between capsaicin-pretreated and vehicle-pretreated rats. In study 2, gastric mucosal blood flow, measured by means of hydrogen gas clearance, and the hemoglobin and oxygen content of the gastric mucosa, as assessed with reflectance spectrophotometry, were not significantly different in the two groups of anesthetized portal-hypertensive rats pretreated with capsaicin or vehicle. In study 3, we confirmed the effectiveness of neonatal capsaicin pretreatment by measuring calcitonin gene-related peptide content of the gastric corpus wall. Capsaicin pretreatment caused a depletion of calcitonin gene-related peptide by at least 98% compared with that in vehicle-pretreated rats. These results do not support a role of capsaicin-sensitive sensory neurons that innervate the gastrointestinal tract in the development of the splanchnic vasodilatation characteristically observed in chronic portal hypertension.

Animals↗
PubMed1994

Bradykinin-induced sensitization of afferent neurons in the rat paw.

Determination of the thermal nociceptive threshold in the rat hind paw was used to investigate the participation of postganglionic sympathetic neurons and of capsaicin-sensitive afferent neurons to bradykinin-induced thermal hyperaesthesia. Intraplantar injection of 0.5 microgram bradykinin or of 0.3 microgram prostaglandin E2 significantly lowered paw withdrawal latencies, whereas injection of [des-Arg9]bradykinin was ineffective. The B-2 receptor antagonist HOE 140 (0.1 mg/kg) prevented bradykinin- but not prostaglandin E2-induced thermal hyperaesthesia. While morphine (1 mg/kg) antagonized the effect of bradykinin and prostaglandin E2, indomethacin (10 mg/kg) reduced only bradykinin-induced sensitization. Although this can be taken as indication that bradykinin-induced sensitization of heat-sensitive fibres is mainly mediated via local prostanoid formation, we failed to obtain evidence for an involvement of sympathetic postganglionic fibres in this process: chemical sympathectomy, which lowered the tissue concentration of noradrenaline by more than 90%, did not influence the ability of bradykinin to induce a decrease in thermal nociceptive threshold. The target of bradykinin/prostaglandin E2 action seemed to be capsaicin-sensitive afferents, since in rats which had been treated with capsaicin to destroy this group of afferents, both substances were completely ineffective in producing sensitization. We suggest therefore that in the rat paw, bradykinin, independently from sympathetic postganglionic neurons, lowers the thermal nociceptive threshold mainly via B-2 receptor-mediated formation of cyclo-oxygenase products which, in turn, act exclusively on capsaicin-sensitive afferent neurons.

Animals↗
PubMed1992

Time-course of capsaicin-evoked release of calcitonin gene-related peptide from rat spinal cord in vitro. Effect of concentration and modulation by Ruthenium Red.

The capsaicin-evoked release of calcitonin gene-related peptide (CGRP) from rat superfused dorsal spinal cord slices was investigated during sustained capsaicin exposure thought to represent equilibrium conditions. The dose-effect relationship for total peptide release evoked by single capsaicin doses (26 min exposure) was very steep with a threshold at 0.06 microM and a maximum at 0.3 microM capsaicin. With concentrations of capsaicin within this range the slow decline of the peptide release in the presence of capsaicin was not a consequence of exhaustion of an available peptide pool nor of neuronal impairment because potassium depolarization was still able to release CGRP. In contrast, with concentrations of capsaicin at 1.5 microM and above, there was a much faster decay of the release after the peak, most probably due to a loss of the secretion capacity caused by neuronal inactivation. When cumulative dose regimens for capsaicin were employed, release of CGRP could be stimulated only up to a dose of 1-1.5 microM capsaicin; further increase in capsaicin concentration was ineffective. This was also most probably due to a loss of the secretion capacity caused by neuronal inactivation and not caused by depletion of a releaseable peptide pool. Release of CGRP evoked by capsaicin concentrations in the range of 0.1-0.3 microM in either dosage protocol was reduced in the presence of Ruthenium Red (RR, 2.5 microM). RR did not reduce neuropeptide release evoked by capsaicin concentrations at or above 1-1.5 microM, nor did it affect the inactivation of the release process at such high capsaicin concentrations. The results demonstrate that, upon sustained exposure to capsaicin, different ranges of concentration can be established at which either only stimulatory or a mixture of stimulatory and inhibitory effects determine the amount of neuropeptides released.

Animals↗
PubMed1992

CP-96,345, a non-peptide antagonist of substance P: II. Actions on substance P-induced hypotension and bronchoconstriction, and on depressor reflexes in mammals.

In order to extend the in vivo pharmacological profile of CP-96,345 ((2S,3S)-cis-2-(diphenylmethyl)-N-((2-methoxyphenyl)- methyl)-1-azabicyclo[2.2.2]octan-3-amine dihydrochloride), a non-peptide antagonist of substance P, the compound was tested against substance P-induced effects on blood pressure in rabbits and on respiration pressure in guinea-pigs. In addition, CP-96,345, and its inactive (2R,3R)-enantiomer, CP-96,344, were also tested in 2 models involving presumably substance P-mediated reflexes in the rat. The fall in blood pressure evoked by i.v. injections of substance P in the rabbit was inhibited by 0.3 mumol kg-1 CP-96,345 i.v. for at least 30 min, and almost abolished, for at least 2 h, by 3 mumol kg-1. In guinea-pigs, the bronchoconstriction induced by i.v. injections of substance P, but not that in response to histamine or bradykinin, was inhibited by CP-96,345 (0.6 and 6.0 mumol kg-1, i.v.) in a dose-dependent manner and this inhibition lasted for 40 min and 70 min, respectively. CP-96,345 (3-20 mumol kg-1, i.v.) reduced depressor reflexes in response to stimulation of peripheral capsaicin-sensitive neurones in the rat. However, the inhibition was not dose-dependent and was also seen with the inactive enantiomer, CP-96,344. This effect can hardly be attributed to receptor-specific effects of CP-96,345 and may be related to unspecific actions such as those involved in the cardiac depression exhibited by both enantiomers. The present results show that CP-96,345 is a potent antagonist of substance P in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

CP-96,345, a non-peptide antagonist of substance P. III. Cardiovascular effects in mammals unrelated to actions on substance P receptors.

The cardiovascular effects of CP-96,345, a non-peptide antagonist of substance P, were analyzed in vivo and in vitro. In the anaesthetized rat, the i.v. injection of 3 mumol kg-1 of CP-96,345 induced a fall in mean arterial blood pressure and a reduction in heart rate. Similar effects were obtained with the enantiomer CP-96,344 (2R,3R)-cis-isomer of CP-96,345) which does not interact with substance P receptors. Both enantiomers, at a concentration of 10 microM, decreased the beating frequency of the isolated atria and of the isolated perfused heart of the guinea-pig to a similar extent, and caused transient coronary dilatation. CP-96,345 (10 microM) decreased the spontaneous sinus rate, prolonged the atrioventricular-nodal conduction interval and the His-bundle conduction interval of the perfused guinea-pig heart. The intraventricular spread of conduction was markedly inhibited. During programmed stimulation 10 min after the beginning of the drug application, the effective refractory periods evaluated by stimulation with premature beats, as well as rate dependent effective refractory periods, of the atrioventricular node, of the atrial and of the ventricular myocardium, were prolonged. Sinus node recovery time was also prolonged. It was concluded that these cardiac effects of CP-96,345 were not caused by an action of the compound on substance P receptors.

Anesthesia↗
PubMed1992

Effect of noradrenergic denervation by neonatal DSP-4 on peptide neurotransmitter systems in the rat brain.

The specific effects of a neonatal treatment of rats with the noradrenergic neurotoxin DSP-4 were investigated in the adult rat by measuring monoamine and peptide transmitter levels in eight brain regions. When applied concomitantly with a 5-hydroxytryptamine uptake blocker, neonatal DSP-4 induced a selective depletion of noradrenaline (NA) in cortex, hippocampus and amygdala. An increase of NA was observed in the medulla and substantia nigra/ventral tegmental area and a decrease in dopamine was observed in the thalamus. The vasoactive intestinal polypeptide levels were markedly elevated in the DSP-4 treated rats in almost all CNS regions whereas those of three other neuropeptides remained unchanged. It is concluded that certain adaptational changes can be observed in the peptide systems of the CNS upon disruption of the development of the noradrenergic innervation.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1992

Increased content and transport of substance P and calcitonin gene-related peptide in sensory nerves innervating inflamed tissue: evidence for a regulatory function of nerve growth factor in vivo.

The responses of sensory neuropeptides during unilateral, Freund's adjuvant-induced, paw inflammation in the rat were examined. After five days of inflammation, the substance P and calcitonin gene-related peptide content in the sciatic nerve supplying the inflamed paw were increased by 60-75% when compared with the contralateral side. At this time-point, there was also a 30-40% increase in the substance P and calcitonin gene-related peptide content of the dorsal root ganglia (L4-L6), and a 40% increase in the calcitonin gene-related peptide content of the L4-L6 segments of the dorsal spinal cord on the inflammation side. In the dorsal root ganglia, calcitonin gene-related peptide content was also increased as early as 12 h and 48 h after induction of paw inflammation. On day 5 of inflammation, the axonal transport of both sensory neuropeptides towards the inflamed paw, as determined after sciatic nerve ligation, was also markedly increased as compared with the control side. Despite this increased transport, the amount of substance P and calcitonin gene-related peptide present in the inflamed paw itself was either reduced or remained unchanged from day 1 through to day 5 of inflammation pointing towards reduced storage and increased release of the peptides in the inflamed tissue. Nerve growth factor content was markedly increased in the sciatic nerve of the inflamed paw with a peak of +136% at time-point 24 h after induction of inflammation. When rats were systemically treated with anti-nerve growth factor serum, the increase in neuropeptide content in the sciatic nerve of the inflamed paw (day 5) was prevented. On the other hand, local injections of nerve growth factor for 5 days into a noninflamed paw were able to induce an increase in substance P and calcitonin gene-related peptide content in the supplying sciatic nerve. These findings point towards a regulatory function for nerve growth factor in vivo in the stimulation of sensory neuropeptide synthesis during prolonged inflammatory processes.

Animals↗
PubMed1992

The non-peptide tachykinin antagonist, CP-96,345, is a potent inhibitor of neurogenic inflammation.

1. Release of the tachykinin, substance P, from the peripheral terminals of polymodal afferent C-fibres is thought to be largely responsible for the vasodilatation and plasma protein extravasation described as neurogenic inflammation. The effects of CP-96,345, a non-peptide antagonist at the substance P (NK1) receptor, on these vascular reactions were investigated in the rat. 2. Intravenously (i.v.) injected CP-96,345 (0.4-3.0 mumol kg-1) prevented the drop in blood pressure, a measure of the peripheral vasodilatation, evoked by substance P and neurokinin A in a dose- and time-dependent manner, but did not affect that elicited by the non-tachykinin peptides calcitonin gene-related peptide and vasoactive intestinal polypeptide. 3. Plasma protein extravasation evoked by i.a. infusion of substance P, antidromic stimulation of the saphenous or the vagus nerve, and stimulation of cutaneous afferent nerves with mustard oil, were each significantly inhibited by CP-96,345 (3.0-9.0 mumol kg-1, i.v.). Furthermore, CP-96,345 was orally active in blocking mustard oil-induced plasma extravasation with an ED50 of 10 mumol kg-1. 4. The inhibition of substance P-induced vasodilatation and of neurogenic plasma extravasation by CP-96,345 was stereospecific as the inactive isomer CP-96,344 (2R, 3R enantiomer of CP-96,345) had no effect. 5. Thus CP-96,345 is a specific, highly potent, long-acting and orally active inhibitor of tachykinin-mediated neurogenic inflammation.

Animals↗
PubMed1991

Depolarization-evoked release of glutamate, aspartate and gamma-aminobutyric acid from rat dorsal spinal cord slices does not originate from capsaicin-sensitive neurons.

A release of endogenous glutamate (Glu), aspartate (Asp) and gamma-aminobutyric acid (GABA) from rat dorsal spinal cord slices was evoked by a 60 mM K(+)-depolarization (calcium dependent) and by 50 microM veratridine (tetrodotoxin sensitive) indicating a neuronal exocytosis mechanism. No release of the 3 amino acids investigated was obtained with the selective C-fiber excitant capsaicin (1 microM) and after impairment of afferent C-fibers the amount of amino acids released by K(+)-depolarization or veratridine was not reduced. These results suggest that amino acids may be exclusively transmitters of capsaicin-insensitive nerve structures in the rat dorsal spinal cord.

Animals↗
PubMed1991

Neurogenic and non-neurogenic inflammation in the rat paw following chemical sympathectomy.

Rats with chemical sympathectomy, induced either at neonatal age (long-term sympathectomy) or in adult animals (short-term sympathectomy) by guanethidine or by 6-hydroxydopamine, were used to determine the contribution of sympathetic noradrenergic fibres to afferent neuron-mediated responses and to non-neurogenic inflammation in the rat. Following long-term sympathectomy with 6-hydroxydopamine there was a 66% depletion of noradrenaline in the paw skin. This was accompanied by a 20-53% increase in the levels of sensory neuropeptides in the paw skin and sciatic nerve. A hypersensitivity towards heat stimuli was observed in the tail immersion test. Neither neurogenic plasma protein extravasation following antidromic nerve stimulation or upon local mustard oil application nor the development of the non-neurogenic carrageenan oedema and its susceptibility towards indomethacin were impaired. Neonatal guanethidine sympathectomy caused an 86% depletion of noradrenaline in the paw skin and neurogenic plasma protein extravasation upon antidromic nerve stimulation was impaired. Sensory neuropeptides were unchanged in the skin after neonatal guanethidine and only calcitonin gene-related peptide content was increased in the spinal cord and sciatic nerves. The other observations (i.e. the sensitivity towards heat stimuli, the neurogenic mustard oil inflammation and the non-neurogenic carrageenan oedema) were similar to those observed after neonatal 6-hydroxydopamine treatment. Following the short-term treatment protocol of 6-hydroxydopamine, an 82% depletion of noradrenaline in the skin was accompanied by an increase in calcitonin gene-related peptide content, whereas after adult guanethidine (60% depletion of noradrenaline) levels of sensory neuropeptides were unchanged. Neurogenic plasma protein extravasation was found to be unimpaired after either type of short-term chemical sympathectomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗
PubMed1991

Sensory pharmacology.

During the last decade, evidence has been accumulated to demonstrate that a subpopulation of peptide-containing primary afferent neurones serve a dual sensory-efferent function. Considerable effort has been put into the development of pharmacological tools to modulate the release and/or the postjunctional effects of transmitters of primary afferents. This commentary summarizes the different approaches designated to achieve this goal, which, if successful, will lead to true 'sensory pharmacology'.

Animals↗