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At least 667 records · Page 37Linked to original sources
PubMed1984

Tail-pinch method in vitro and the effects of some antinociceptive compounds.

An in vitro preparation for testing antinociceptive drugs is described. The preparation consists of isolated spinal cord, spinal nerve roots and functionally connected tail of the newborn rat. Noxious pressure stimulation given to the tail induced in a lumbar ventral root a depolarizing response of 1-2 mV lasting about 15-30 s, which is referred to as tail-pinch potential. Single shock stimulation of a lumbar dorsal root induced in the ipsilateral ventral root of the same segment monosynaptic and polysynaptic reflexes, which were followed by a depolarizing response lasting ca. 20 s. The latter slow response is referred to as ipsilateral slow ventral root potential (VRP). Morphine, [Met5]enkephalin, [Leu5]enkephalin and [D-Ala2,Met5]enkephalinamide depressed both the tail-pinch potential and the ipsilateral slow VRP, but did not exert any noticeable effect on the monosynaptic and polysynaptic reflexes. The effects of morphine and enkephalins were completely abolished by naloxone. Naloxone potentiated the tail-pinch potential and the ipsilateral slow VRP in the fresh preparations which had not been exposed to opiate compounds or enkephalins, suggesting that the endogenous enkephalinergic mechanism occurs in the spinal cord and modulates the incoming nociceptive signals. The present isolated spinal cord-tail preparation will be useful for studying actions of analgesic drugs and for screening compounds for analgesic effects.

Analgesics↗
PubMed1983

Pig sperm tail tubulin. Its extraction and characterization.

Axonemal tubulin extracted from pig sperm tails has been characterized by one- and two-dimensional electrophoresis and by one-dimensional peptide mapping. The electrophoretic mobilities of its subunits after reduction and carboxymethylation were similar to those of the major subunits of pig brain tubulin. Sperm tail tubulin subunits also had roughly the same isoelectric points as pig brain tubulin subunits, except that they appeared to have a relatively larger tailing effect. The proteolytic cleavage pattern of the pig sperm tail beta-tubulin closely resembled those of both the tunicate (Ciona intestinalis) sperm beta-tubulin and pig brain beta-tubulin. The peptide pattern of pig sperm tail alpha-tubulin, however, was more similar to that of tunicate sperm tail alpha-tubulin than to that of pig brain alpha-tubulin. This supports the hypothesis put forward in a previous investigation [1] that functionally similar tubulins from taxonomically distant species can be more related than functionally dissimilar tubulins from the same species.

Animals↗
PubMed1989

Is the pineal involved in the stimulatory influence of prolactin on tail regeneration in lizards? Studies with exogenous prolactin in lizards exposed to continuous darkness.

We have recently demonstrated that continuous light stimulates tail regeneration in the gekkonid lizard, Hemidactylus flaviviridis, whereas continuous darkness and pinealectomy depress regeneration. As a sequel to this observation, the effect of exogenous ovine prolactin (oPRL) on tail regeneration in normal (NL) and pinealectomized (PX) Hemidactylus exposed to continuous darkness (L:D 0:24) during the monsoon season was investigated. Once-daily intraperitoneal (ip) injections of 500 micrograms/kg oPRL were administered to a group of NL lizards, a group of PX lizards, and a group of sham-PX (sPX) lizards, 5 days prior to tail autotomy and 50 days afterward. Three groups--PX, sPX, and NL animals--served as the controls and received once-daily ip injections of 0.6% saline. Our observations show that initiation of regeneration, daily growth rate, total length of new growth (regenerate) at the end of regeneration, and total percentage replacement of lost (autotomized) tail were all significantly enhanced in oPRL-treated NL lizards as compared with their saline-treated (NL, PX, and sPX) and oPRL-treated (PX and sPX) counterparts. It is suggested that PRL may be the active factor that speeds up the rate of tail regeneration in lacertilians. The role of the pineal organ in vertebrate photoreception and the possibility that in Hemidactylus the presence of an intact pineal is somehow linked with the favorable influence of PRL on tail regeneration are discussed.

Animals↗
PubMed1983

Stimulation of spinal dopaminergic receptors: differential effects on tail reflexes in rats.

The tail-flick reflex to heat and tail-withdrawal reflex to touch were measured in spinal and intact rats given either apomorphine (0.02-1.75 mumol.kg-1) or dopamine (0.02-1.76 mumol.kg-1) in the lumbar subarachnoid space. In spinal rats both apomorphine and dopamine suppressed thermal tail-flick reflex and enhanced tactile tail-withdrawal response in a dose-dependent way. The effect of apomorphine in spinal rats was counteracted by dopaminergic receptor antagonists (cis-flupenthixol and (+)-butaclamol), but not by their stereoisomers. Phenoxybenzamine, propranolol, methysergide and naloxone failed to counteract the effects of apomorphine on tail-reflex responses in spinal rats. (+)-Butaclamol also counteracted effects of dopamine in spinal rats. Neither apomorphine nor dopamine influenced tail reflexes in intact rats, which suggests that effects of spinal dopaminergic mechanisms on these reflexes are influenced by descending supraspinal pathways.

Animals↗
PubMed1982

Tail pinch behavior and analgesia in diabetic mice.

Mild tail pinch induced "consummatory" behaviors in mice. The major tail pinch behavior appeared to be chewing with food ingestion occurring possibly as an epiphenomenon. All tail pinch behaviors were obliterated by the dopamine antagonist haloperidol; and the opiate antagonist, naltrexone, decreased eating without altering chewing. The combination of dopamine blockade and tail pinch induced jumping behavior in mice. Diabetic mice showed increased tail flick latencies to radiant heat and to the induction of tail pinch behaviors, displaying these behaviors less commonly than their homozygote and heterozygote littermate controls.

Animals↗
PubMed1982

Tail pinch induced consummatory behaviors are associated with analgesia.

Pinching the tail of a rat results in a set of consummatory behaviors including chewing, eating and licking. In the present study, the effect of tail pinch on pain thresholds was evaluated using the hot-plate and writhing tests. Continuous tail pinch resulted in chewing and markedly lengthened the latency to hind-paw licking and jumping (hot-plate test) when compared with control rats and totally eliminated writhing behaviors. Tail pinch (which induced chewing) for one minute prior to the analgesic testing also prolonged the latency of hot plate-induced behaviors and suppressed the number of writhing behaviors. Naloxone reversed the tail pinch induced analgesia as measured by the hot-plate test, but did not reverse tail pinch-induced analgesia as measured by the writhing test.

Analgesia↗
PubMed1991

Effects of local anesthesia and intravenous naloxone on the changes in behaviour and plasma concentrations of cortisol produced by castration and tail docking with tight rubber rings in young lambs.

The reliability of some behavioral and physiological indices used for the recognition and assessment of acute pain in lambs after castration and tail docking has been examined. Changes in the indices were measured after blocking neural activity with local anaesthetic (lignocaine) and after an opioid antagonist (naloxone) was administered. Six lambs, aged less than one week, were allocated randomly to each of six treatments. (i) control handling and blood sampling; (ii) castration plus tail docking with tight rubber rings; (iii) local anaesthesia; (iv) local anaesthesia followed by castration and tail docking; (v) intravenous naloxone only (0.2 mg kg-1); and (vi) intravenous naloxone followed by castration and tail docking. Local anaesthesia eliminated the behavioural and plasma cortisol changes which usually follow castration and tail docking. Naloxone had a limited effect on the increase in cortisol but altered the behaviour. The results support the view that such indices are useful for assessment of the response to acute pain and that, although endogenous opioids do reduce pain in young lambs after castration and tail docking, the effect is small.

Anesthesia, Local↗
PubMed1991

Tail-cuff detection of systolic hypertension in different strains of ageing rats.

To identify rat strains suitable for studying age-related development of hypertension we compared pressures measured with the tail-cuff method in different groups of ageing Fischer 344, Wistar, or Sprague-Dawley rats. Preliminary experiments to establish optimal frequency of chronic blood pressure measurement in ageing rats showed that tail-cuff systolic pressures did not differ significantly whether taken weekly or monthly. Repeated tail-cuff measurements were comparable even when a common cuff size was used in different groups of rats with varying tail diameters. Additional studies were then carried out in 1-year old male Wistar and Sprague-Dawley rats to measure tail-cuff pressures monthly during the second year of age. Systolic and mean pressures increased progressively with age in both strains, as did body weight and heart rate, but the incidence of hypertension was higher in Sprague-Dawley than in Wistar rats. Elevations in mean pressures were sometimes more pronounced than those in systolic pressure. Two months after the last tail-cuff measurement, the presence of hypertension in Wistar rats was verified by the elevated mean pressures that were recorded from femoral artery catheters. Our results overall suggest that the predisposition to hypertension was higher in Sprague-Dawley than in Wistar or Fischer 344 rats of the same age, and also in males than in females of the same strain. Of all the different strains and sexes we compared, therefore, male Sprague-Dawley rats from 20 to 24 months of age may be the best model for studying the development of systolic hypertension with age.

Aging↗
PubMed1989

Nicotine-induced tail-tremor and drug effects.

Tail-tremor induced by repeated and daily administration (0.5 mg/kg SC x 6 times/day) of nicotine as well as effects of various drugs on this response were investigated in Wistar strain male rats. Daily administration of nicotine in doses of 0.5 mg/kg SC caused tail-tremors to appear beginning on the 3rd day. Tail-tremor induced by the first injection of each day gradually increased with the daily injections, however, the heightened effect of this first injection at the beginning of each day decreased during the day upon repeated administration of 6 times/day at 2-hr intervals. Basically, tail-tremor appeared about 5 min after SC administration of nicotine and reached a peak approximately 7-9 min after injection, declining to zero afterwards. Different drugs showed various effects on this response. While mecamylamine (0.5 and 1.0 mg/kg IP) abolished nicotine-induced tail-tremor, arecoline (0.5 and 1.0 mg/kg IP), atropine (2.5 and 5.0 mg/kg IP), scopolamine (1.0 and 2.0 mg/kg IP) and hexamethonium (0.5 and 1.0 mg/kg IP) showed no such effects. Furthermore, physostigmine (0.1 mg/kg IP) actually potentiated this action. These results suggest that tail-tremor induced by nicotine may be mediated through central nicotine receptor system.

Animals↗
PubMed1991

Tail-tremor induced by exposure to cigarette smoke in rats.

Tremors appearing only in the tail (tail-tremor) induced by cigarette smoke and subcutaneous nicotine were investigated using a smoking machine and Wistar rats. Daily exposure (twice a day) to smokes of two commercial cigarettes (Mild-Seven Select for the first 7 days and Long-Peace for the next 6 days) caused the tail-tremor to appear even if it was slight. A single subcutaneous nicotine (0.5 mg/kg) administration to rats exposed to the cigarette smokes for 13 days markedly caused the tail-tremor. On the other hand, daily subcutaneous injection of nicotine (0.5 mg/kg/day) also caused the tail-tremor to appear beginning on the 4th day and the incidence of tremor increased to 100% by the 12th day. These results indicate that tail-tremor can be caused not only by daily subcutaneous administration of nicotine but also by daily exposure to cigarette smoke.

Animals↗
PubMed1988

Endothelium-dependent dilatation of the ex vivo tail artery perfused with blood from a conscious rat.

A comparison was made of the endothelium-dependent vasodilatation produced by acetylcholine (Ach) in rat-tail arteries perfused with Krebs solution or whole rat blood. Segments of the tail artery of the rat were cannulated at both ends mounted in an organ bath and perfused at a constant 3 ml/min. Blood perfused the tail artery via an extra corporeal circuit by being withdrawn from and returned to a conscious donor rat previously prepared with exteriorized indwelling carotid artery and jugular vein cannulae. Perfusion pressure was increased by constricting the tail artery with an infusion of noradrenaline into the perfusate. In arteries perfused with Krebs solution, the infusion for 1 min of Ach at 10(-6) M maximally reduced perfusion pressure. However, when arteries were perfused with blood, the infusion of Ach calculated to produce a concentration of 10(-5) M in the blood, produced very little response. A higher concentration, 10(-4) M, produced a maximal dilatation. Treatment of the donor rat with 0.02 mg/kg physostigmine IV potentiated the response to 10(-5) M Ach. In Krebs-perfused vessels, physostigmine 10(-6) M did not potentiate Ach responses. Methacholine, which is more resistant to cholinesterase, was more potent than Ach in blood-perfused tail arteries. Removal of the endothelium of the tail artery blocked responses to Ach in the blood-perfused vessels. It is concluded that Ach can produce an endothelium-dependent dilatation in a vessel perfused with whole blood, although Ach in blood is susceptible to inactivation by cholinesterase.

Acetylcholine↗
PubMed1980

Prolactin and tadpole metamorphosis. Evidence of prolactin receptors in premetamorphic Rana catesbeiana liver and tail fin.

The binding characteristics of ovine prolactin (OPRL) to a particulate fraction from liver and tail fin of Rana catesbeiana tadpoles were studied. The specific binding of [125I]oPRL to both tissues was found to be a saturable process with a single class of binding sites in each tissue. Although the dissociation constants were similar for each tissue, the tail fin demonstrated a 10-fold higher binding capacity than the liver tissue. Pretreatment of the liver and tail fin particulate fractions with degradative enzymes revealed that trypsin and phospholipase C reduced the subsequent specific [125I]oPRL binding in both tissues. However, neuraminidase treatment decreased the prolactin binding in the liver while having no effect on the tail fin. The binding of prolactin to the amphibian tissues was found to be specific for prolactin and growth hormones. [125I]oPRL binding to both tissues was a reversible process although the dissociation rate was faster for the tail fin than for the liver. Therefore, prolactin receptors are associated with both a prolactin responsive tissue, the tail, and an unresponsive tissue, the liver, in the tadpole.

Animals↗
PubMed1986

Hyperalgesia following ischaemia of the rat's tail.

We have investigated the effects of ischaemia on responses to a subsequent noxious stimulus in rats. Tail flick latencies to a noxious thermal stimulus were determined by immersing the tail in water at temperatures ranging from 39 to 49 degrees C. We then produced ischaemia by occluding the blood supply to the tail; ischaemia was terminated at the first signs of an escape response. Tail flick latencies were recorded immediately after termination of ischaemia and at 30 min intervals for another 2 h. Each rat acted as its own control. Tail flick latency decreased after ischaemia; we found a decrease of about 39% immediately after ischaemia, at immersion temperatures above 39 degrees C. The duration of the hyperalgesia increased with increasing water temperatures. Thus noxious ischaemia of the rat tail induced hyperalgesia to subsequent noxious thermal stimuli. The hyperalgesia could have arisen through either central or peripheral mechanisms.

Animals↗
PubMed1976

Thyroxine-binding proteins in liver and tail of Rana catebeiana undergoing metamorphosis.

Presence of a thyroxine-binding protein was demonstrated in vivo in cell sap of tail and liver of metamorphosing Rana catesbeiana tadpoles. Thyroxine-binding protein was not present in tail of prematamorphic tadpoles while it appeared during progressing metamorphosis roughly coinciding with the beginning of tail resorption. Susceptibility to pronase indicates that this thyroxine-binding macromolecule is protein in nature. Thyroxine-binding in liver was already present during premetamorphic stages and increased further during metamorphosis. A further difference between tail and liver thyroxine-binding protein was evidenced by molecular sieve chromatography on Sephadex G-200 indicating a molecular weight of thyroxine-binding protein in the tail of 60 000 as opposed to 42 000 for liver. Scatchard analysis of tail cell sap of tadpoles in metamorphic climax revealed a high affinity thyroxing binding site (Kd of 2 - 10(-10) M) of low capacity (1.7 pmol per mg protein) while tadpoles in premetamorphic stage had a thyroxine-binding site of lower affinity (9 - 10(-10) M) and higher capacity (4.8 pmol per mg protein). Thus affinity of thyroxine binding is 4-fold in metamorphic climax and appears to reflect the appearance of thyroxine binding observed in vivo.

Animals↗
PubMed1998

Antinociception produced by microinjection of morphine in the rat periaqueductal gray is enhanced in the foot, but not the tail, by intrathecal injection of alpha1-adrenoceptor antagonists.

Antinociception produced by microinjection of morphine in the ventrolateral periaqueductal gray is mediated in part by alpha2-adrenoceptors in the spinal cord dorsal horn. However, several recent reports demonstrate that microinjection of morphine in the ventrolateral periaqueductal gray inhibits nociceptive responses to noxious heating of the tail by activating descending neuronal systems that are different from those that inhibit the nociceptive responses to noxious heating of the feet. More specifically, alpha2-adrenoceptors appear to mediate the antinociception produced by morphine using the tail-flick test, but not that using the foot-withdrawal or hot-plate tests. The present study extended these findings and determined the role of alpha1-adrenoceptors in mediating the antinociceptive effects of morphine microinjected into the ventrolateral periaqueductal gray using both the foot-withdrawal and the tail-flick responses to noxious radiant heating in lightly anesthetized rats. Intrathecal injection of selective antagonists was used to determine whether the antinociceptive effects of morphine were modulated by alpha1-adrenoceptors. Injection of the selective alpha1-adrenoceptor antagonists prazosin or WB4101 potentiated the increase in the foot-withdrawal response latency produced by microinjection of morphine in the ventrolateral periaqueductal gray. In contrast, either prazosin or WB4101 partially reversed the increase in the tail-flick response latency produced by morphine. These results indicate that microinjection of morphine in the ventrolateral periaqueductal gray modulates nociceptive responses to noxious heating of the feet by activating descending neuronal systems that are different from those that inhibit the nociceptive responses to noxious heating of the tail. More specifically, alpha1-adrenoceptors mediate a pro-nociceptive action of morphine using the foot-withdrawal response, but in contrast, alpha1-adrenoceptors appear to mediate part of the antinociceptive effect of morphine determined using the tail-flick test.

Adrenergic alpha-Antagonists↗
PubMed1998

Segmental origin of sympathetic preganglionic neurones regulating the tail circulation in the rat.

The spinal segments of origin of the sympathetic preganglionic neurones (SPNs) influencing the activity of sympathetic postganglionic neurones innervating the tail have been studied using a neurophysiological approach. Activity was recorded from the ventral collector nerve that carries 70% of the sympathetic fibres innervating targets within the tail and provides 80% of the innervation of the caudal ventral artery. When recording activity from the ventral collector nerve at the tail base, the largest responses were evoked following electrical stimulation within spinal segments lumbar (L) 1 and 2 and smaller responses from thoracic (T) 13 (n = 5). Although similar responses to those recorded from the tail base were elicited from spinal segments L1 and L2, when activity was recorded from mid-tail only minimal responses were evoked from T13 (n = 6). On average robust responses were never elicited following stimulation beyond these segments. Responses had latencies compatible with conduction over C-fibre axons and were absent following ganglionic blockade. It is concluded that SPNs influencing the tail circulation reside mainly in L1 and L2 spinal segments and there is also a substantial but lesser contribution arising from segment T13.

Animals↗
PubMed2001

Raphe magnus/pallidus neurons regulate tail but not mesenteric arterial blood flow in rats.

In urethane-anesthetized rats with body temperature maintained at 39-40 degrees C, electrical stimulation of raphe magnus/pallidus/parapyramidal region within 0.5 mm of the ventral medullary surface reduced arterial blood flow to the tail cutaneous bed (measured with a chronically implanted Doppler ultrasonic flowmeter) from 28+/-5 to 6+/-1 cm/s (P<0.01), without changing mesenteric arterial blood flow, and with only small, variable changes in arterial pressure. Injection of bicuculline (50 pmol in 50 nl) at the same site reduced tail flow from 19+/-2 to 3+/-1 cm/s (P<0.01), again without significantly changing mesenteric flow, but with a moderate increase in arterial pressure. When the rat was cooled to reduce basal tail blood flow, injection of muscimol (1 nmol in 100 nl) or GABA (100 nmol in 100 nl) into the raphe site restored tail blood flow to 93+/-4% of the pre-cooling level. These recordings are the first reported direct measurements of rat tail blood flow changes elicited by alteration of neuronal function in the brainstem. The rostral medullary raphe controls the tail cutaneous vascular bed in a relatively selective manner. Our findings add to evidence that raphe magnus/pallidus/parapyramidal neurons are involved in regulating cutaneous blood flow in response to changes in body temperature in the rat.

Animals↗
PubMed2003

Corticotropin-releasing factor as well as opioid and dopamine are involved in tail-pinch-induced food intake of rats.

Several kinds of stress such as psychological stress, restraint, and foot shock inhibit feeding behavior through corticotropin-releasing factor (CRF). In contrast, a mild tail pinch increases food intake in rats. Although dopamine and opioid are thought to be involved in tail-pinch-induced food intake, it is unknown whether CRF participates in this phenomenon. Therefore, we attempted to clarify this issue using rats. A 30-s tail pinch increased food intake in 30 min after the tail pinch, and this increase was blocked by intraperitoneal injection of CRF receptor type 1 selective antagonist. CRF increased food intake in 30 min after intracerebroventricular injection at a dose of 2 or 10 ng, and this increase was also blocked by CRF receptor type 1 antagonist. Tail-pinch- or CRF-induced food intake was blocked by naloxone, pimozide, and spiperone. These results suggest that CRF, through CRF receptor type 1 as well as opioid and dopaminergic systems, are involved in the mechanism of tail-pinch-induced food intake. The results also suggest that brain CRF has dual effects on food intake, hyperphagia and anorexia, in a stress-dependent manner.

Animals↗