Drugs in sport.

This themed issue of the British Journal of Pharmacology has been compiled and edited by Ian McGrath, Regius Professor of Physiology at University of Glasgow and David Cowan, Director of the Drug Control Centre at King's College London. It contains 11 articles covering the mechanisms of action of the major groups of drugs used illicitly in sport. The articles, written by experts in how drugs work, set out where drugs can or cannot affect sporting performance, how this relates to their legitimate medicinal use, their other detrimental effects and how they can be detected. Publication coincides with Olympic year, when sport is highlighted in the public mind and much speculation is made concerning the use of drugs. The articles provide a framework of expert, accurate knowledge to inform and facilitate these debates and to help to overcome the ill-informed and dangerous anecdotal information by which sports men and women are persuaded to misuse drugs in the mistaken belief that this will improve their performance without present or future ill effects. A unique article is included by the Spedding brothers, Mike with a long career in drug discovery and Charlie, the 1984 Los Angeles Olympic Marathon Bronze Medallist and still the English National Marathon record holder. From their unique experience, they describe the insidious and unfair way that drug-assisted performance undermines the ethos of sport and endangers the vital place of sport in maintaining the health of the population.

Alpha(1A)-adrenoceptors mediate contractions to phenylephrine in rabbit penile arteries.

BACKGROUND AND PURPOSE: Maintained penile erection depends on the absence of alpha-adrenoceptor (alpha-AR) activation and so can be facilitated by alpha-blockers. This study seeks the alpha(1)-AR subtypes involved in order to inform the pro-erectile consequences of subtype selective blockade. EXPERIMENTAL APPROACH: Wire myography was used with dorsal (nutritional supply) and cavernous (erectile inflow) penile arteries; standard alpha-AR-selective agonists and antagonists were employed to classify responses. KEY RESULTS: In both penile arteries noradrenaline (NA) and phenylephrine (PE, alpha(1)-AR agonist) caused concentration-dependent contractions. Sensitivity to NA was increased by NA uptake blockers, cocaine (3 microM) and corticosterone (30 microM). PE responses were antagonised by phentolamine (non-selective alpha-AR: dorsal pK(B) 8.00, cavernous 8.33), prazosin (non-subtype-selective alpha(1)-AR: dorsal 8.60, cavernous 8.41) and RS100329 (alpha(1A)-AR selective: dorsal 9.03, cavernous 8.80) but not by BMY7378 (alpha(1D)-AR selective: no effect at 1-100 nM) or Rec15/2615 (alpha(1B)-AR selective: no effect at 1-100 nM). Schild analysis was straightforward in cavernous artery, indicating that PE activates only alpha(1A)-AR. In dorsal artery Schild slopes were low, though alpha(1A)-AR was still indicated. Analysis using UK 14,304 and rauwolscine indicated an alpha(2)-AR component in dorsal artery that may account for low slopes to alpha(1)-AR antagonists. CONCLUSIONS AND IMPLICATIONS: Penile arteries have a predominant, functional alpha(1A)-AR population with little evidence of other alpha(1)-AR subtypes. Dorsal arteries (nutritional supply) also have alpha(2)-ARs. Thus, alpha-AR blockers with affinity for alpha(1A)-AR or alpha(2)-AR would potentially have pro-erectile properties; the combination of these perhaps being most effective. This should inform the design of drugs to assist/avoid penile erection.

Phase I and pharmacokinetic study of LM985 (flavone acetic acid ester).

We have conducted a Phase I and initial clinical pharmacological evaluation of LM985, the first of a series of compounds based on the flavone ring structure to be considered for clinical trial in malignant disease. The drug was administered i.v. to 26 patients with advanced cancer on an every-21-day schedule. Patients were treated at 14 dosage levels ranging from 10 to 1500 mg/m2. Dose limiting toxicity was identified as acute reversible hypotension occurring during drug infusion; no leukopenia, alopecia, hepatic toxicity, or renal toxicity was observed, but at the higher dose range, mild sedation was apparent. Twenty patients had measurable disease and were evaluable for response. One patient with colorectal carcinoma had stable disease after three courses of LM985; however, no other responses were seen. Pharmacokinetic and in vitro drug degradation studies imply that the ester LM985 is hydrolyzed to LM975 (flavone acetic acid) rapidly in vivo. LM975 is active in a variety of animal tumor models, but it does not have the cardiovascular side effects seen with LM985 (hypotension and bradycardia) in pithed or anesthetized rats. We would recommend that LM975 be considered for clinical trial, because it seems likely that substantially higher doses of LM975 than of LM985 can be given without dose limiting cardiovascular toxicity.

Angiotensin-converting enzyme-independent contraction to angiotensin I in human resistance arteries.

BACKGROUND: In vitro studies of myocardial tissue suggest that angiotensin II (Ang II) may be generated by both ACE and chymase. A similar dual pathway may exist in the vasculature. We studied the effects of ACE and chymase inhibitors on the contractile response to angiotensin I (Ang I) in human resistance arteries to investigate ACE-independent generation of Ang II. METHODS AND RESULTS: Subcutaneous resistance arteries (250 to 350 microm) were obtained from gluteal biopsies from volunteers and New Zealand White rabbits and mounted on a wire myograph. Contractile ability was tested with high-potassium depolarization and norepinephrine 10 micromol/L and endothelial integrity by relaxation to acetylcholine 3 micromol/L. Cumulative concentration-response curves were constructed for Ang I in the presence of enalaprilat 1 micromol/L, chymostatin 10 micromol/L, or both inhibitors together. In the rabbit, enalaprilat completely inhibited the Ang I response. In human vessels, enalaprilat or chymostatin alone had no effect, but the combination of enalaprilat and chymostatin almost completely inhibited the response to Ang I. CONCLUSIONS: A dual pathway for Ang II generation exists in human resistance arteries, mediated by ACE and a chymostatin-sensitive enzyme, probably chymase. We confirm that a marked species difference exists in the mechanism of Ang II generation between the human and the rabbit. More efficacious suppression of the renin-angiotensin system may require development of novel enzyme inhibitors or combinations of currently available drugs.

Indomethacin, but not oxygen tension, affects the sensitivity of isolated neonatal rabbit ductus arteriosus, but not aorta, to noradrenaline.

The effects of increasing oxygen tension from fetal to neonatal levels and of incubation in the cyclo-oxygenase inhibitor, indomethacin, on the response of isolated rings of neonatal rabbit ductus arteriosus and aorta to noradrenaline were studied in vitro. Increasing oxygen tension did not affect the sensitivity, as measured by the pEC50, of either vessel to noradrenaline. Incubation with indomethacin increased ductal sensitivity to noradrenaline tenfold, but had no effect on the aortic response. Since indomethacin caused the ductus arteriosus to contract (by the removal of dilator prostaglandins), the effect of increased muscular tone per se on the response to noradrenaline was investigated by eliciting a contracture by potassium induced depolarisation. This procedure did not alter the vessel's sensitivity to noradrenaline and reduced its maximum response (indomethacin had increased the maximum response). It is concluded that intramurally synthesised cyclo-oxygenase products, most probably prostaglandins, attenuate the sensitivity of the ductus arteriosus to noradrenaline.

Characterisation of the effect of oxygen tension on response of fetal rabbit ductus arteriosus to vasodilators.

OBJECTIVE: The aims of the study were (1) to elucidate the effects of raised oxygen tension on the response of the ductus arteriosus to a range of vasodilators; and (2) to establish the effect, if any, of cyclo-oxygenase inhibition on the interaction between oxygen and prostaglandin (PG)E2. METHODS: Rings of ductus arteriosus were isolated from fetal New Zealand White rabbits at 28 d gestation (term = 31) and precontracted with 10 microM noradrenaline in the presence of the cyclo-oxygenase inhibitor indomethacin (1 microM). Cumulative relaxation response curves were obtained from a range of vasodilators and their pEC50 (-log10 of the interpolated molar concentration causing 50% of the maximum response) and maximum relaxant response (MRR) were determined in 15% oxygen (neonatal oxygen tension, 13-14.3 kPa) and 2% oxygen (fetal oxygen tension, 2.5-3.0 kPa). In addition, the effects of (1) omitting indomethacin and (2) its substitution by 1 microM flubriprofen were studied on the interaction between oxygen and PGE2. RESULTS: In 1 microM indomethacin, nifedipine and atrial natriuretic peptide had no effect on ductal tone in either oxygen tension. In 15% oxygen, the rank order of MRR was forskolin > cicaprost > PGE2 >> cromakalim >> sodium nitroprusside approximately adenosine approximately 0. The MRR of all agonists was increased in 2% oxygen except forskolin which caused complete relaxation in 15% oxygen. In 15% oxygen, the rank order of pEC50 was PGE2 >> cicaprost approximately cromakalim approximately forskolin. PGE2 was 70.8 times more potent than cicaprost. The pEC50 of all four agonists was increased in 2% oxygen. The increase in pEC50 could not be explained by a decreased extent of precontraction. The MRR to PGE2 in 15% oxygen and the magnitude of the increase in pEC50 to PGE2 going from 15% to 2% oxygen were the same in 1 microM flubriprofen, 1 microM indomethacin, or in the absence of these drugs. However, in 2% oxygen, the MRR to PGE2 was increased in 1 microM indomethacin or 1 microM flubriprofen compared with control. CONCLUSIONS: (1) Increasing oxygen tension from fetal to neonatal levels desensitises the ductus arteriosus to a range of vasodilators. (2) There is evidence that prostacyclin has a physiological role in the control of the rabbit ductus arteriosus. (3) The effect of oxygen on the potency of PGE2 is independent of cyclo-oxygenase products, whereas its effect on the efficacy of PGE2 is modulated by an endogenous cyclo-oxygenase product.

Increased alpha(1)- and alpha(2)-adrenoceptor-mediated contractile responses of human skeletal muscle resistance arteries in chronic limb ischemia.

OBJECTIVE: Recently, we have shown augmented contractile responses of skeletal muscle resistance arteries to noradrenaline in patients with critical limb ischemia. We investigated whether this increased sensitivity in skeletal muscle resistance arteries is due to either alpha(1)- or alpha(2)-adrenoceptor-mediated responses or both. METHODS: Skeletal muscle resistance arteries were isolated from the proximal (non-ischemic) and distal (ischemic) parts of limbs amputated for critical limb ischemia and mounted on a small vessel wire myograph. Cumulative concentration response curves of the vessel segments to noradrenaline, phenylephrine and brimonidine were obtained in the presence or the absence of the selective antagonists, prazosin and RS79948. RESULTS: Noradrenaline and phenylephrine produced almost equal maximal contractile responses. Brimonidine responses were smaller and were almost abolished by 0.1 microM RS 79948 while those of phenylephrine and noradrenaline were not affected. Prazosin reduced the maximum responses to brimonidine, shifted the concentration response curves of noradrenaline and phenylephrine rightwards giving pK(B) values of 9.86 and 9.33, respectively. Maximum responses produced by all three agonists in distal vessels were significantly higher than those obtained in proximal vessels. CONCLUSIONS: Noradrenaline contractile responses in skeletal muscle resistance arteries are predominantly mediated by alpha(1)-adrenoceptors. Both alpha(1)- and alpha(2)-adrenoceptor-mediated responses are increased in the arteries from ischemic regions that may aggravate the decreased blood flow to the limbs due to arterial occlusion.

NOS inhibition potentiates norepinephrine but not sympathetic nerve-mediated co-transmission in resistance arteries.

OBJECTIVE: The in vitro interaction between sympathetic nerves and basal nitric oxide release was studied in a resistance artery, since these interact powerfully in large vessels. METHODS: The pharmacological interaction between L-NAME and vasoconstriction to field stimulation of sympathetic nerves or exogenous norepinephrine was studied in rabbit cutaneous resistance arteries in wire myographs. RESULTS: Relaxation of norepinephrine-induced tone by acetylcholine, but not sodium nitroprusside, was blocked by N omega-nitro-L-arginine methyl ester (L-NAME: 100 microM), indicating that the agonist-induced release of nitric oxide could oppose the vasoconstrictor effect of norepinephrine and confirming that L-NAME had no effect on endothelium-independent vasodilatation. L-NAME increased norepinephrine potency indicating basal NO release. With short bursts of electrical field stimulation purinergic transmission was dominant at low frequencies and adrenergic at high frequencies. L-NAME had no effect on nerve-mediated responses, even after blocking the purinergic component with alpha,beta-methylene ATP (3 microM), suggesting that the influence of spontaneously released nitric oxide does not extend to the vascular smooth muscle cells under adrenergic nervous control. CONCLUSION(S): This resistance artery exhibits a highly effective nitric oxide-mediated vasodilatation to acetylcholine. It has basal release of nitric oxide which antagonises exogenous norepinephrine. However, basal nitric oxide did not influence adrenergic nerve transmission, which contrasts with previous studies of larger arteries and veins. We speculate that in small resistance arteries there may be a spatial limitation to the zones of vascular smooth muscle influenced by the adrenergic nerves and by basal nitric oxide from the endothelium, respectively. The role of endogenous nitric oxide in modulating vascular tone may thus be less in resistance arteries than in conducting arteries or capacitance vessels and purinergic transmission appears to be particularly resistant.

BJP is linking its articles to the IUPHAR/BPS Guide to PHARMACOLOGY.

LINKED EDITORIALS: This Editorial is part of a series. To view the other Editorials in this series, visit: http://onlinelibrary.wiley.com/doi/10.1111/bph.12956/abstract; http://onlinelibrary.wiley.com/doi/10.1111/bph.12954/abstract; http://onlinelibrary.wiley.com/doi/10.1111/bph.12955/abstract and http://onlinelibrary.wiley.com/doi/10.1111/bph.12856/abstract. VIDEO: To view the video on the IUPHAR/BPS Guide to PHARMACOLOGY, visit: https://www.youtube.com/watch?v=Qhy3q33VtRI.

Cellular aspects of vascular remodeling in hypertension revealed by confocal microscopy.

Cellular aspects of remodeling in intact arteries have not been fully investigated, mainly due to the lack of an appropriate methodology that allows for simple measurements. The aim of this study was to develop a method based on laser scanning confocal microscopy (LSCM), compare it with previous methodology, and apply it to the study of remodeling in hypertension. The morphology of mesenteric resistance arteries from stroke-prone spontaneously hypertensive rats (SHRSP) and Wistar-Kyoto rats (WKY) was determined with wire myography on one segment with a standardized diameter setting (0.9[d100]) and with perfusion myography on a second segment from the same artery at the calculated equivalent pressure. The second segments were stained with the nuclear dye Hoechst 33342 (live tissue) or propidium iodide (fixed tissue) and measured with LSCM and MetaMorph software. Compared with wire myography, perfusion myography showed similar differences from those previously reported. Compared with LSCM, perfusion myography showed a similar lumen but significantly smaller wall thickness in both live and fixed tissue, probably due to measurement underestimation. In the study with LSCM, arteries from SHRSP compared with those from WKY showed (1) reduced lumen, (2) altered cell density that was significantly increased in the adventitia, decreased in the media, and unchanged in the intima, (3) significantly increased medial volume, (4) significantly smaller endothelial cell nuclei, and (5) adventitial-like cells in the media. We conclude that (1) LSCM is a reliable and straightforward method to study morphology in intact vessels, (2) it provides new information on the cellular changes in remodeling, (3) adventitia might play an active role in the process of remodeling in hypertension, and (4) endothelium "remodels" in hypertension.

Angiotensin II causes vascular hypertrophy in part by a non-pressor mechanism.

Angiotensin II, when given in low doses, raises blood pressure slowly. When tested in vitro on vascular smooth muscle cells, it has mitogenic and trophic effects; it is not known if it has these effects in vivo. Our purpose was to determine whether vascular hypertrophy develops during slow pressor infusion of angiotensin II and, if so, whether it is pressure induced. Three experiments were done in rats infused subcutaneously with angiotensin II (200 ng/kg/min) by minipump for 10-12 days. Experiment 1: Angiotensin II gradually raised systolic blood pressure (measured in the tail) from 143 +/- 2 to 208 +/- 8 mm Hg (mean +/- SEM), significantly suppressing plasma renin and increasing threefold (NS) plasma angiotensin II. There was no loss of peptide in the pump infusate when tested at the end of the experiment. Experiment 2: In the perfused mesenteric circulation, vasoconstrictor responses to norepinephrine, vasopressin, and KCl were enhanced in rats given a slow pressor infusion of angiotensin II, but sensitivity of responses was not altered. This combination of changes suggests that vascular hypertrophy develops during slow pressor infusion of angiotensin II. Experiment 3: Vessel myography was done after angiotensin II infusion with and without a pressor response. Angiotensin II raised systolic blood pressure, increased heart weight, and produced myographic changes of vascular hypertrophy in the mesenteric circulation, increasing media width, media cross-sectional area, and media/lumen ratio. Hydralazine given with angiotensin II prevented the rise of pressure and the cardiac effect but not the vascular changes. Two-way analysis of variance showed that angiotensin II significantly increased media width, media cross-sectional area, and media/lumen ratio, all independent of hydralazine. Thus, although hydralazine inhibits the pressor and cardiac effects of angiotensin II, suggesting a pressor mechanism for the cardiac change, it does not inhibit structural vascular change, which suggests that at least part of the effect has a non-pressor mechanism.

Functional reduction and associated cellular rearrangement in SHRSP rat basilar arteries are affected by salt load and calcium antagonist treatment.

The stroke-prone spontaneously hypertensive rat (SHRSP) is a strain with high incidence of cerebrovascular accidents increased by salt-rich diet and decreased by calcium-antagonist treatment. In the SHRSP rat basilar artery the authors have previously shown reduced contractility and altered structure including regions of smooth muscle cell (SMC) disorganization. The aims of this study have been to analyze (1) the morphology of these abnormal regions, (2) the structural modifications responsible for the reduced function, and (3) the effect of salt and calcium-antagonist treatment on vascular structure and function. Wistar Kyoto and SHRSP rats, untreated or treated from week 8 through 14 with 1% NaCl or 1% NaCl + 1 mg x kg(-1) x d(-1) lacidipine, were used. Function was studied with wire myography. Structure was analyzed in fixed intact arteries with confocal microscopy. Basilar arteries from SHRSP rat showed (1) reduced contractility, (2) discrete foci of SMC disarray with altered proportion of adventitia to SMC, and (3) decreased SMC and increased adventitial cell number. Arteries from salt-loaded SHRSP rats showed a higher degree of SMC disarray and further reduction in contractility. Lacidipine treatment of salt-loaded rats significantly improved structure and function. These data suggest that vascular remodeling can provide an explanation for the observed reduction in vascular contractility of SHRSP rat basilar arteries and might show light on the effects of salt load and calcium-channel blockers in life span and the incidence of cerebrovascular accidents in SHRSP rats.

Cellular changes induced by chronic nitric oxide inhibition in intact rat basilar arteries revealed by confocal microscopy.

BACKGROUND: Cellular aspects of remodelling have not been investigated fully in intact vessels due to lack of appropriate methodology. OBJECTIVE: To determine the cellular alterations induced by chronic inhibition of nitric oxide (NO) production in intact rat basilar arteries by combined use of perfusion myography and a laser scanning confocal microscope. METHODS: Wistar-Kyoto rats were treated with 10 mg/kg per day NG-nitro-L-arginine methyl ester (L-NAME) for 3 weeks. Basilar arteries from treated and age-matched Wistar-Kyoto rat controls were mounted on a perfusion myograph, stained with the nuclear dye Hoechst 33342 and fixed under pressure. The segments were mounted on a slide and visualized using the 364 nm line of a laser scanning confocal microscope. MetaMorph software was used to obtain optical sections from the vessel and for morphology determinations. RESULTS: L-NAME treatment induced hypertension (systolic blood pressure control 129.2+/-2.7 mmHg and SBP L-NAME treatment 176.3+/-5.2 mmHg, P< 0.001). Compared with control rat arteries, arteries from treated rats had a reduced lumen diameter, similar wall thickness and an increased wall: lumen ratio. L-NAME treatment induced specific changes in adventitia, media and intima, namely an increase in number of adventitial cells and in adventitia thickness, a reduction in number of smooth muscle cells with no change in media thickness and reductions in number of endothelial cells, size of nuclei and luminal surface area. CONCLUSIONS: Hypertension induced by chronic inhibition of NO production is associated with eutrophic remodelling of rat basilar artery. However, within this overall maintenance of constant volume, there are marked cellular changes in adventitia, media and intima. The separate contributions of inhibition of NO production and hypertension to the remodelling process need to be elucidated.

Alpha-adrenoceptor antagonism by apoyohimbine and some observations on the pharmacology of alpha-adrenoceptors in the rat anococcygeus and vas deferens.

alpha-Adrenoceptor antagonism of several test drugs was assessed against adrenergic contractile responses to field stimulation in rat vas deferens and anococcygeus, the prejunctional inhibitory effect of xylazine in vas deferens and the contractile effects of alpha-adrenoceptor agonists in anococcygeus. Against the adrenergic nerve-induced contraction in vas deferens, the potency series was WB 4101 greater than prazosin greater than apoyohimbine greater than corynanthine greater than yohimbine greater than rauwolscine. Against the inhibitory effect of xylazine in vas deferens the potency series was apoyohimbine greater than rauwolscine = yohimbine greater than WB 4101 much greater than prazosin and corynanthine. In anococcygeus, against the contractile responses to adrenergic nerve stimulation or to the agonists amidephrine, noradrenaline and xylazine, the potency series was apoyohimbine greater than corynanthine greater than rauwolscine. These results show that apoyohimbine is more potent than the yohimbine sterioisomers as an antagonist at alpha 1- and alpha 2-adrenoceptors but is not more selective. The assay methods employed confirm the current classification of 'alpha'-receptors and drugs.

The effect of hypoxia on neuroeffector transmission in the bovine retractor penis and rat anococcygeus muscles.

The effects of reducing the PO2 of the bathing fluid were studied on non-adrenergic non-cholinergic (NANC) transmission in isolated preparations of the bovine retractor penis muscle, the rat anococcygeus muscle, the guinea-pig taenia caeci and the guinea-pig urinary bladder. Hypoxia rapidly and reversibly impaired NANC transmission in the bovine retractor penis and rat anococcygeus muscles but did not affect transmission in the guinea-pig taenia caeci or bladder, suggesting that different NANC mechanisms are involved. Although neurally-evoked relaxation of the bovine retractor penis was impaired by hypoxia, relaxations produced by vasoactive intestinal peptide, prostaglandin E1, sodium nitroprusside or an inhibitory factor isolated from the bovine retractor penis were unaffected. Since the inhibitory factor is similar to, and may actually be the NANC transmitter, the results suggest that the site of action of hypoxia in impairing transmission is prejunctional at the inhibitory nerve endings.

Post-natal development of functional neurotransmission in rat vas deferens.

Responses of the rat vas deferens to drugs and to field stimulation were examined in sexually immature rats. The vasa from immature rats often exhibited spontaneous contractions and displayed greater sensitivity to the contractile effects of alpha-adrenoceptor agonists. The responses of the vasa from immature rats to single pulse field stimulation lacked the adrenergic component of the response although the non-adrenergic component was present. The responses were antagonized by alpha 2-adrenoceptor agonists. In the presence of cocaine, an adrenergic component of the response did appear. During trains of pulses the pre- and postjunctional effects of adrenergic transmission which are found in adult rats were absent in vasa from immature rats. Electron microscopic studies showed no qualitative differences in adrenergic innervation in vasa from immature and adult rats. It is concluded that a state of 'pre-innervation supersensitivity' associated with a lack of functional adrenergic transmission exists in the vas deferens of immature rats. The supersensitivity disappears and functional transmission develops during the period in which testosterone secretion increases in the rat. The reason for the lack of functional transmission at a time when the innervation appears to be morphologically mature is not clear but may be due to the noradrenaline release mechanism not being fully operative.

The actions of cirazoline on the rat vas deferens.

The pre- and postsynaptic effects of the alpha 1-agonist cirazoline were assessed in epididymal and prostatic portions of the rat isolated vas deferens. Cirazoline produced a postsynaptic alpha 1-adrenoceptor mediated potentiation of the isometric contraction to single pulse field stimulation in both prostatic and epididymal portions. In epididymal portions, nifedipine (10 microM) greatly attenuated the postsynaptic alpha 1-receptor mediated potentiation of nerve mediated contractions, uncovering a presynaptic inhibitory action of cirazoline . No evidence was found for alpha 2-antagonism by cirazoline . It is concluded that the previously reported antagonism of the presynaptic inhibitory effects of clonidine was due to postsynaptic potentiation of nerve-mediated responses by cirazoline .

Effects of ketamine on the peripheral autonomic nervous system of the rat.

The effects of ketamine (2-(o-chlorophenyl) 2-methylaminocyclohexanone) (2-50 mg/kg) on the responses of the pithed rat arterial pressure, anococcygeus muscle and colon to selective stimulation of the spinal autonomic outflows were examined. Ketamine depressed the vasopressor response produced by stimulation of the lumbar sympathetic outflow in a dose-dependent manner but did not significantly affect the pressor response to intravenous noradrenaline (NA) administration. Ketamine depressed the motor responses of the anococcygeus to stimulation of the pre-ganglionic lumbar sympathetic outflow or to stimulation of post-ganglionic fibres in the sacral region in a dose-dependent manner, the response to preganglionic stimulation being relatively more sensitive to such depression. The anococcygeus response to NA was significantly potentiated with doses of ketamine of 20 mg/kg and 50 mg/kg. Ketamine depressed the motor response of the smooth muscle of the colon to stimulation of the sacral parasympathetic outflow in a dose-dependent manner and at lower doses than were required to produce an equivalent depression of the sympathetic responses in the other tissues. A comparison was made of the effects of ketamine and cocaine on the motor responses of the anococcygeus muscle in vitro to NA, carbachol and field stimulation. Both ketamine and cocaine produced a non-specific depression of all responses at high doses whereas cocaine but not ketamine produced a large potentiation of NA and motor nerve responses at lower doses. The results are discussed in relation to the hypothesis that ketamine might elevate blood pressure in conscious animals and man by potentiating vascular adrenergic responses.

The effects of lysergic acid diethylamide on the response to field stimulation of the rat vas deferens and the rat and cat anococcygeus muscles.

1. The effect of lysergic acid diethylamid (LSD) on the response to field stimulation in vitro of the rat vas deferens and anococcygeus muscle was examined. 2. LSD in concentrations from 10(-9) to 10(-6) M caused an increase in tone or rhythmic activity in both tissues, effects identical to those produced by guanethidine or tyramine. The motor effects of all three drugs were abolished by phentolamine 2 x 10(-6) M. Methysergide 2 x 10(-7) M given before LSD reduced the motor effect but was ineffective once the LSD contraction had developed. 3. LSD 10(-9) to 10(-6) M reduced and eventually abolished the response to motor adrenergic nerve stimulation in the anococcygeus muscle with no effect on the response to noradrenaline (NA) and no evidence of differential sensitivity according to the number of stimulating pulses. In the vas deferens LSD abolished the initial twitch component with no effect on the secondary slow contraction. LSD had no effect on the response to inhibitory nerve stimulation in the anococcygeus. 4. These results suggest that in the anococcygeus LSD closely resembles guanethidine in its effects as an adrenergic neurone blocking drug with indirect sympathomimetic actions. In the vas deferens these properties would explain the block of the initial twitch component in the motor response to field stimulation and the increase in rhythmic activity but do not explain the resistance of the secondary slow component of the motor response.

The response of the cat anococcygeus muscle to nerve or drug stimulation and a comparison with the rat anococcygeus.

1 The cat anococcygeus muscle is shown to possess a dual innervation similar to the rat anococcygeus, with a motor adrenergic innervation and an inhibitory innervation whose transmitter is unknown. The pharmacological properties of the cat muscle were investigated and compared with those of the rat muscle.2 The cat muscle contracts to noradrenaline, 5-hydroxytryptamine, tyramine, amphetamine, guanethidine, cocaine and lysergic acid diethylamide (LSD). The effects of noradrenaline and 5-hydroxytryptamine are blocked by phentolamine and methysergide respectively.3 The cat anococcygeus is relaxed by acetylcholine, carbachol, isoprenaline, ATP, prostaglandins E(1), E(2) and F(2alpha) and vasopressin, all of which contract the rat muscle. The effects of acetylcholine and carbachol are blocked by atropine and those of isoprenaline by propranolol.4 Field stimulation produces contraction of the cat anococcygeus, which is blocked by phentolamine and guanethidine but unaffected by hexamethonium, atropine or neostigmine.5 In the presence of guanethidine (10(-5)M), the tone of the muscle is raised and field stimulation produces relaxation of the muscle. These inhibitory responses are unaffected by phentolamine, hexamethonium, atropine or neostigmine.6 Neostigmine potentiates the effects of acetylcholine, but not of carbachol in relaxing the cat anococcygeus and in contracting the rat anococcygeus, but has no effect on either motor or inhibitory responses to field stimulation.7 Cold storage for up to eight days had little effect on either the motor response to noradrenaline or the motor or inhibitory response to field stimulation of the cat anococcygeus. Beyond eight days, the response to field stimulation diminishes more rapidly than the response to noradrenaline.