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Biomedical subjects

F K Pierau

Publications and source records attributed to F K Pierau.

At least 19 recordsLinked to original sources
PubMed1995

Choline acetyltransferase-immunoreactive neurones in a prevertebral sympathetic ganglion, the inferior mesenteric ganglion.

Using immunohistochemical techniques a small population of choline acetyltransferase (ChAT) immunoreactive (IR) neurones has been identified in the inferior mesenteric ganglion (IMG) of guinea pig (4.6% of all neurones), ferret (6.4%) and rat (0.4%). A detailed study in the guinea-pig IMG revealed that the vast majority of cholinergic neurones did not express tyrosine hydroxylase (TH)-IR, indicating that they were non-catecholaminergic. The cholinergic neurones were significantly larger than the TH-positive neurones. The majority of the ChAT-IR cells (64%) was observed in small clusters which were consistently located in the caudal lobe of the IMG close to the entry of the hypogastric nerves. 83% of the ChAT-IR cells also contained neuropeptide Y (NPY). Since the vast majority of TH-negative cells were ChAT-positive (94%), the TH negativity was taken as an indirect indication for ChAT-IR. NPY-IR, somatostatin (SOM)-IR and vasoactive intestinal peptide (VIP)-IR were found in both the TH-IR cells (22, 84 and 1%, respectively) and the putative cholinergic population (95, 84 and 70, respectively). Thus the majority of cholinergic neurones in the IMG were likely to contain NPY, SOM and VIP. TH-IR cells exhibited an extensive innervation of fibers immunoreactive for ChAT, VIP, ENK and NOS. In contrast, only a sparse plexus of ChAT-, ENK-, NOS-, NPY- and SOM-positive fibres was found around the TH-negative cells. VIP-IR fibres did not appear to innervate ChAT neurones.

Animals↗
PubMed1993

Distribution and binding sites of substance P and calcitonin gene-related peptide and their capsaicin-sensitivity in the spinal cord of rats and chicken: a comparative study.

In a comparative study, the distribution and binding sites of substance P (SP) and calcitonin gene-related peptide (CGRP) in the spinal cord, and their susceptibility towards capsaicin pretreatment were studied in rats and chicken. Rats: In accordance with the SP immunohistochemistry, specific binding sites for 125I-Bolton-Hunter-SP were highest in laminae I-III. Binding sites for 125I-0Tyr-rat-CGRP were found to be dense around the central canal, moderate in the dorsal and weak in the ventral horn. Neonatal capsaicin pretreatment, that reduced SP and CGRP immunoreactivities, increased SP specific binding sites in laminae I-III and X by 20 and 100%, respectively. An increase in CGRP binding density was detected in laminae IV, V and in the lumbar ventral horn. Displacement studies revealed a significant decrease of EC50-values for SP. Chicken: SP and CGRP immunoreactivities and SP specific binding sites were distributed similarly as in rats. Binding sites for radiolabelled CGRP, however, were highest in lamina X and in the ventral horn. Capsaicin (800 mg/kg) injected into the eggs 9 days before hatching had no influence on growth rate, nociception, peptide immunoreactivities and binding of the respective radioligands. The data demonstrated a different action of capsaicin on SP and CGRP and their specific binding sites in the spinal cord of rats and chicken and were discussed with regard to functional differences between these two animal species.

Animals↗
PubMed1992

Pre-spinal convergence between thoracic and visceral nerves of the rat.

Dichotomizing sensory axons have been demonstrated in a number of species and are of significance in understanding the possible mechanisms underlying referred pain. The present study reviews work employing fluorescent dyes as tracers to demonstrate afferent dichotomization in the peripheral nervous system. Dichotomization between the intercostal and splanchnic nerves of the rat was demonstrated by means of intraneural transport of Diamidino yellow or Fast blue. Frequency of pre-spinal somato-visceral convergence averaged 2% (range 0.1-21%). Average frequency of convergence was 8.3% (range 2-23.1%) between internal and external intercostal nerves. Control experiments in which axoplasmic transport was inhibited by vinblastine ruled out the possibility of errors from non-axoplasmic transport of the markers. Thoraco-visceral pre-spinal convergence occurs in the rat and is variable in extent.

Afferent Pathways↗
PubMed1992

An opioid peptide inhibits capsaicin-sensitive vasodilatation in the pig's skin.

Microcirculatory effects of electrical stimulation of nerves through a pair of needle electrodes in the skin of anaesthetized pigs were studied by using the laser Doppler flowmetric method. Electrical stimulation (0.3-30 Hz) evoked a short-lasting decrease in capillary blood flux (vasoconstriction) followed by an increase (vasodilatation), of longer duration. Vasoconstriction was inhibited by local guanethidine, but not by capsaicin pretreatment, whereas vasodilatation was blocked by local capsaicin, but not by guanethidine. Both phases of the response were suppressed by local application of tetrodotoxin. Thus, vasoconstriction due to electrical stimulation seems to be of sympathetic origin, while vasodilatation is a result of a release of vasoactive substances from capsaicin-sensitive nerve endings. Vasodilatation due to electrical stimulation was strongly and dose-dependently inhibited by the opioid peptide [D-Met2,Pro5] enkephalinamide, while vasoconstriction remained apparently unchanged. At both doses of the opioid peptide tested (0.03 and 0.15 mumol/kg i.m.) inhibition of vasodilatation was larger at lower than at higher frequencies of stimulation. Guanethidine pretreatment did not influence the inhibitory action of [D-Met2,Pro5] enkephalinamide. Naloxone (1.5 mumol/kg i.m.) reversed or prevented the inhibitory action of the opioid peptide; naloxone on its own did not influence responses due to 0.3-30 Hz stimulation. [D-Met2,Pro5] enkephalinamide (0.15 mumol/kg i.m.) did not influence basal blood flux in the skin, mean arterial blood pressure, respiratory minute volume or respiratory frequency. It was concluded that stimulation of opioid receptors by [D-Met2,Pro5] enkephalinamide is likely to inhibit stimulation-evoked vasodilatation by reducing the release of vasoactive substances from capsaicin-sensitive afferent neurons, an effect that does not depend on functional integrity of sympathetic nerves. Endogenous opioids probably do not modulate the capsaicin-sensitive vasodilatation.

Animals↗
PubMed1992

Substance P and calcitonin gene-related peptide in the ureter of chicken and guinea-pig: distribution, binding sites and possible functions.

To elucidate the possible functional significance of sensory neuropeptides in visceral organs of mammals and birds the distribution, binding sites and the effects on ureteric peristalsis of substance P and calcitonin gene-related peptide (CGRP) were investigated in the ureter of guinea-pigs and chickens. In the guinea-pig numerous substance P and CGRP-immunoreactive fibres were located in the adventitia, smooth muscle layer, submucosa and occasionally in the epithelium. Varicose peptidergic fibres were often found on blood vessels. Binding sites for substance P were associated with blood vessels and epithelium in the following density order: venules greater than epithelium greater than arterioles. The highest density of CGRP binding sites was detected on the smooth muscle; venules and arterioles expressed moderate binding. The peristalsis frequency of the isolated ureter of the guinea-pig was increased by neurokinin A and substance P, whereas CGRP inhibited ureteric motility. In the chicken the immunoreactivity to substance P and CGRP was less pronounced. Immunoreactive fibres were found in the submucosa close to the epithelium and around ureteric ganglion cells. Correspondingly, substance P binding sites were located in the epithelium and in ureteric ganglia; however, specific CGRP binding was restricted to large blood vessels. In the chicken none of the sensory neuropeptides affected ureteric motility. Only high doses of the sensory neurotoxin capsaicin (greater than 10 microM) repeatedly produced a non-specific inhibitory effect, similar to that found in a capsaicin-desensitized guinea-pig ureter preparation. The data suggest that in the guinea-pig ureter sensory neuropeptides play a modulatory role in the regulation of ureteric motility and might have vascular and epithelial functions. In the chicken, substance P might be involved in the regulation of epithelial function and modulation of ganglionic transmission. The physiological or pathophysiological role of sensory neuropeptides and the efferent functions of afferent fibres appears to be much better developed in the guinea-pig than in the chicken.

Animals↗
PubMed1992

The effect of PGE2 on activity and thermosensitivity of hypothalamic neurones in rat brain slices.

Using brain slices the effect of prostaglandin E2 (PGE2) on neurones from different locations of the rat hypothalamus was analysed. PGE2 (150 ng), when injected into the perfusion chamber, influences all hypothalamic neurones studied. The pattern of firing rate changes after PGE2 is variable, but the depressive effect predominates--72% of neurones decrease their firing rate in long-term experiments. PGE2 also lowers the thermosensitivity of warm sensitive neurones and increases the thermosensitivity of temperature insensitive neurones.

Animals↗
PubMed1991

Recent advances in research on sensory peptides and capsaicin mechanisms. A conference report.

A mini-symposium (chaired by L. Chal, Australia, P. Lembeck, Austria, J. Szolcsányi, Hungary and M. Zimmermann, F.R.G.) was held in Bad Nauheim, F.R.G. on June 29, 1990, under the sponsorship of the European Neuropeptide Club, which focussed on recent advances of research on sensory peptides and mechanism of action of capsaicin. Attention was paid to both the sensory and 'efferent' functions of these primary afferents, to the detection of pathophysiologically relevant stimuli for their activation and to the development of new pharmacological tools for research in this field.

Afferent Pathways↗
PubMed1990

Thioctic acid induces dose-dependent sprouting of neurites in cultured rat neuroblastoma cells.

Quantitative computer-assisted evaluation of thioctic acid-induced sprouting in Neuro-2a cells reveals a clear dose dependence with respect to several parameters of sprouting. At first predominantly the length of main sprouts per cell (neurites from cell soma to first branching) and the number of branchings per cell are increased. With the higher dosages, the length of branches per cell rises considerably, too. In contrast, the degree of branching (mean length of neurites per branching) seems to be independent of the concentration of thioctic acid. The capacity of thioctic acid to induce sprouting is discussed in terms of the involvement of SH groups and with regard to regeneration phenomena as they may occur in diabetogenic neuropathy.

Animals↗
PubMed1989

Effects of capsaicin in rat and pigeon on peripheral nerves containing substance P and calcitonin gene-related peptide.

Substance P and calcitonin gene-related peptide were immunohistochemically identified in axons innervating the cornea and the ureter of adult rats and pigeons. The two neuropeptides were similarly distributed in both species. Capsaicin pretreatment induced depletion of the immunoreactivity; this was quantitatively and qualitatively different in rats and pigeons. Topical application of capsaicin (1%) reduced the immunoreactivity in the cornea in both species by 50%. Systemic capsaicin treatment completely depleted both peptides from the corneal innervation of rats but reduced the peptide content only by 50% in the cornea of pigeons. In the ureter of rats, capsaicin pretreatment completely depleted the peptide immunoreactivity. In pigeons the peptide depletion was only complete in the outer longitudinal muscle layer. Whereas only a few immunoreactive fibres were observed in the circular muscle layer, about 50% of the peptide remained in the inner longitudinal muscle layer. The results demonstrate that peptidergic afferents in the cornea and ureter of pigeons are sensitive to capsaicin, although birds do not show nociceptive responses to local administration of the drug. The long-term depletion of substance P and calcitonin gene-related peptide by capsaicin is discussed with regard to the possibility that functionally capsaicin receptors may exist in the axon but not at nerve endings.

Animals↗
PubMed1987

Comparison between hypothalamic thermoresponsive neurons from duck and rat slices.

Neuronal thermoresponsiveness in the preoptic and anterior hypothalamic (PO/AH) region of a bird and a mammal were compared in vitro by recording the activity of 48 units from ducks and 37 units from rats in tissue slices subjected to temperature changes. Warm-responsive units were found in similar proportions in duck and rat PO/AH slices. The average degrees of thermoresponsiveness did not differ between the two species. Neurons exhibiting thresholds of warm responsiveness had higher threshold temperatures (2P less than 0.01) in duck (38.8 +/- 0.2 degrees C) than in rat (37.4 +/- 0.4 degrees C) slices (means +/- standard errors). Firing rates at threshold temperatures and thermoresponsiveness below and above thresholds did not differ between ducks and rats. During synaptic blockade in a Ca2+-free/high-Mg2+ medium, warm-responsiveness was retained in 9 out of 13 units in duck slices and in 8 out of 13 units in rat slices. In two instances in ducks and in one case in rats positive temperature coefficients were converted into negative temperature coefficients. Among two cold-responsive units tested in duck slices one retained its cold-responsiveness. It is concluded that in vitro evaluation of PO/AH neuronal thermoresponsiveness in a bird and a mammal has not revealed differences at the single unit level which might explain the diverging contributions of the avian and mammalian hypothalamus to deep body temperature perception.

Action Potentials↗
PubMed1987

The influence of capsaicin on membrane currents in dorsal root ganglion neurones of guinea-pig and chicken.

The effect of capsaicin on voltage-dependent membrane currents of isolated dorsal root ganglia (DRG) neurones of guinea-pig and chicken were investigated by the voltage-clamp technique and intracellular perfusion. In both species, administration of capsaicin (3 X 10(-5) M) to the outer surface of the cell membrane reduced the amplitude and accelerated the inactivation of the fast inactivating potassium current. In contrast, 3,4-diaminopyridine (3,4-DAP) reduced the fast potassium current without affecting the inactivation. Combined application of capsaicin and 3,4-DAP was more effective than either drug alone. The slow potassium current was diminished by capsaicin but not affected by 3,4-DAP. Capsaicin (3 X 10(-5) M) applied to the internal surface of the membrane had little effect on the fast outward current but primarily decreased the amplitude of the slow potassium current. Two subpopulations of sodium currents could be demonstrated in guinea-pig neurones according to their tetrodotoxin (TTX) sensitivity. In type I neurones the sodium current was completely blocked by TTX; type II neurones exhibited a TTX-sensitive as well as a TTX-resistant inward current. Capsaicin (3 X 10(-5) M) applied externally reduced the maximal amplitude of both current components. The time course of inactivation was delayed only in the TTX-resistant sodium current. The effect of capsaicin on Na-currents of DRG neurones was similar in guinea-pigs and chicken. In DRG neurones of chicken, only TTX-sensitive currents were observed. In both species the steady-state inactivation of the sodium currents was shifted by capsaicin to more negative potentials.

Animals↗
PubMed1987

Effect of capsaicin upon afferent and efferent mechanisms of nociception and temperature regulation in birds.

(1) Acute capsaicin effects on nociception in the conscious chicken were tested by close arterial injection. The threshold dose to elicit nocifensive and autonomic responses was 50 micrograms, i.e., two to three orders of magnitude higher than in mammals but four times lower than in pigeons. (2) Foot withdrawal from hot water remained unchanged after capsaicin was injected either intravenously in the chicken at a cumulative dose of 600 mg/kg or perineurally at a dose of 100 micrograms into the sciatic nerve of pigeons. (3) Temperature regulation and body temperature in the chicken were not affected by subcutaneous injection of capsaicin, but intravenous infusion at rates of 2-5 or 10-13 mg X min-1 X kg-1 transiently lowered body temperature by 1.5 degrees C and stimulated panting and sometimes vasodilatation of the comb. Repeated capsaicin infusion produced temporary tachyphylaxia but no permanent desensitization. (4) A cumulative dose of 1 g/kg body weight capsaicin reduced the relationship between breathing frequency and respiratory evaporative heat loss in the duck. This deficit was compensated by more pronounced panting and, thus, did not indicate any impairment of temperature regulation. (5) Injection of capsaicin into the sciatic nerve depleted substance P in the dorsal horn of rats. Similar treatment in pigeons caused an increase of substance P immunoreactivity in the dorsal horn. (6) The effects of high capsaicin doses in birds indicate only low susceptibility of afferent neural mechanisms. Some of the effects may be due to a capsaicin action upon efferent neural mechanisms.

Afferent Pathways↗
PubMed1986

Beta-bungarotoxin inhibits a non-inactivating potassium current in guinea pig dorsal root ganglion neurones.

beta-Bungarotoxin (beta-BuTx), at concentrations of 0.45-45 nmol/l, selectively reduced a portion of the noninactivating potassium current (IsK) in dorsal root ganglion neurones of the guinea pig, measured by voltage clamp of internally perfused cells. The average reduction of IsK obtainable with beta-BuTx was 34% and usually not completed within 20 min, but irreversible upon washing for 20 min. The I/V-characteristic of the current blocked by beta-BuTx was almost linear. It is suggested that beta-BuTx selectively blocks a noninactivating subtype of potassium channel.

Animals↗