A1 and A2 adenosine receptor modulation of contractility in the cauda epididymis of the guinea-pig

1. The effects of adenosine receptor agonists upon phenylephrine-stimulated contractility and [³H]-cyclic adenosine monophosphate ([³H]-cyclic AMP) accumulation in the cauda epididymis of the guinea-pig were investigated. The α₁-adrenoceptor agonist, phenylephrine elicited concentration dependent contractile responses from preparations of epididymis. In the absence or presence of the L-type Ca²⁺ channel blocker, nifedipine (10 μM) the non-selective adenosine receptor agonist, 5′-N-ethylcarboxamido-adenosine (NECA, 1 μM) shifted phenylephrine concentration-response curves to the left (4 and 5 fold respectively). Following the incubation of preparations with pertussis toxin (200 ng ml⁻¹ 24 h) NECA shifted phenylephrine concentration-response curves to the right (5.7±0.9 fold).
2. In the presence of phenylephrine (1 μM), NECA and the A₁ adenosine receptor selective agonists, N⁶-cyclopentyladenosine (CPA) and (2S)-N⁶-[2-endo-norbornyl]adenosine ((S)-ENBA) elicited concentration-responses dependent contractions from preparations of epididymis (pEC₅₀ values 8.18±0.19, 7.79±0.29 and 8.15±0.43 respectively). The A₃ adenosine receptor agonists N⁶-iodobenzyl-5′-N-methyl-carboxamido adenosine (IBMECA) and N⁶-2-(4-aminophenyl) ethyladenosine (APNEA) mimicked this effect (but only at concentrations greater than 10 μM). In the presence of 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 30 nM) CPA concentration-response curves were shifted, in parallel to the right (apparent pK_B 8.75±0.88) and the maximal response to NECA was reduced.
3. In the presence of DPCPX (100 nM) the adenosine agonist NECA and the A_2A adenosine receptor selective agonist, CGS 21680 (2-p-(2-carboxyethyl)-phenethylamino-N-ethylcarboxamido adenosine), but not CPA, inhibited phenylephrine (20 μM) stimulated contractions (pIC₅₀ 7.15±0.48). This effect of NECA was blocked by xanthine amine congener (XAC, 1 μM) and the A_2A adenosine receptor-selective antagonist 4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol (ZM 241385; 30 nM).
4. (S)-ENBA (in the absence and presence of ZM 241385, 100 nM), but not NECA or CPA inhibited the forskolin (30 μM)-stimulated accumulation of [³H]-cyclic AMP in preparations of the epididymis of the guinea-pig (by 17±6% of control). In the presence of DPCPX (100 nM) NECA and CGS 21680, but not (S)-ENBA, increased the accumulation of [³H]-cyclic AMP in preparations of epididymis (pEC₅₀ values 5.35±0.35 and 6.42±0.40 respectively), the NECA-induced elevation of [³H]-cyclic AMP was antagonised by XAC (apparent pK_B 6.88±0.88) and also by the A_2A adenosine receptor antagonist, ZM 241385 (apparent pK_B 8.60± 0.76).
5. These studies are consistent with the action of stable adenosine analogues at post-junctional A₁ and A₂ adenosine receptors in the epididymis of the guinea-pig. A₁ Adenosine receptors potentiate α₁-adrenoceptor contractility, an effect blocked by pertussis toxin, but which may not be dependent upon an inhibition of adenylyl cyclase. The epididymis of the guinea-pig also contains A₂ adenosine receptors, possibly of the A_2A subtype, which both inhibit contractility and also stimulate adenylyl cyclase.

     

A1 adenosine receptor modulation of electrically-evoked contractions in the bisected vas deferens and cauda epididymis of the guinea-pig

1. The effects of adenosine receptor agonists upon both electrically-evoked and phenylephrine-induced contractile responses were investigated in the bisected vas deferens and the cauda epididymis of the guinea-pig. Electrical field-stimulation (10 s trains of pulses at 9 Hz, 0.1 ms duration, supramaximal voltage) elicited biphasic and monophasic contractile responses from preparations of bisected vas deferens and cauda epididymis, respectively; these responses were abolished by tetrodotoxin (300 nM).
2. In the prostatic half of the vas deferens the A₁ selective adenosine receptor agonists, N⁶-cyclopentyladenosine (CPA) and (2S)-N⁶-[2-endo-norbornyl]adenosine ((S)-ENBA) and the non-selective A₁/A₂ adenosine receptor agonist, 5′-N-ethylcarboxamidoadenosine (NECA) inhibited electrically-evoked contractions (pIC₅₀±s.e.mean values 6.15±0.24, 5.99±0.26 and 5.51±0.24, respectively). The responses to CPA were blocked by the A₁ adenosine receptor antagonist, 8-cyclopentyl-1,3-dipropylxanthine, DPCPX (100 nM).
3. In the epididymal half of the vas deferens NECA potentiated (at ⩽100 nM) and inhibited (at ⩾1 μM) electrically-evoked contractions. In the presence of the non-selective α-adrenoceptor antagonist phentolamine (3 μM), the α₁-adrenoceptor antagonist, prazosin (100 nM), or at a reduced train length (3 s) NECA inhibited electrically-evoked contractions (pIC₅₀ values 6.05±0.25, 5.97±0.29 and 5.71±0.27, respectively). CPA (at 10 μM) also inhibited electrically-evoked contractions in this half of the vas deferens. In the presence of prazosin (100 nM), CPA also inhibited electrically-evoked contractions (pIC₅₀ 6.14±0.67); this effect was antagonized by DPCPX (30 nM, apparent pK_B 8.26±0.88). In the presence of the P2 purinoceptor antagonist, suramin (300 μM), CPA (up to 1 μM) potentiated electrically-evoked contractions.
4. NECA, CPA and APNEA potentiated electrically-evoked contractions in preparations of cauda epididymis (pEC₅₀ values 7.49±0.62, 7.65±0.74 and 5.84±0.86, respectively), the response to CPA was competitively antagonized by DPCPX (100 nM) with an apparent pK_B value of 7.64±0.64.
5. The α₁-adrenoceptor agonist phenylephrine elicited concentration-dependent contractile responses from preparations of bisected vas deferens and cauda epididymis. NECA (1 μM) potentiated responses to phenylephrine (⩽1 μM) in the epididymal, but not in the prostatic half of the vas deferens. In preparations of epididymis NECA (1 μM) shifted phenylephrine concentration response curves to the left (4.6 fold). In the presence of a fixed concentration of phenylephrine (1 μM), NECA elicited concentration-dependent contractions of preparations of the epididymal half of the vas deferens and of the epididymis (pEC₅₀ values 7.57±0.54 and 8.08±0.18, respectively). NECA did not potentiate responses to ATP in either the epididymal half of the vas deferens or the epididymis.
6. These studies are consistent with the action of stable adenosine analogues at prejunctional A₁ and postjunctional A₁-like adenosine receptors. The prejunctional A₁ adenosine receptors only inhibit the electrically-evoked contractions of purinergic origin (an effect predominant in the prostatic half of the vas deferens). At the epididymis, where electrically-evoked contractions are entirely adrenergic, the predominant adenosine receptor agonist effect is a potentiation of α₁-adrenoceptor-, but not of ATP-induced contractility.

     

Alpha-adrenoceptor modulation of the efferent function of capsaicin-sensitive sensory neurones in guinea-pig isolated atria.

1. Transmural nerve stimulation of guinea-pig atria, obtained from animals pretreated with reserpine (5 mg kg-1, i.p.), in the presence of atropine 1 microM and of the beta-adrenoceptor blocker CGP 20712A 1 microM, induced a positive inotropic effect which was reduced by the calcitonin gene-related peptide (CGRP) antagonist hCGRP-(8-37) and abolished by pretreatment with capsaicin 1 microM. 2. Noradrenaline concentration-dependently (0.01-10 microM) reduced the increase in cardiac contractility induced by transmural nerve stimulation. The inhibitory effect of noradrenaline was antagonized by yohimbine (0.5-1 microM), in a dose-dependent manner. Prazosin (0.5-1 microM) antagonized the effect of noradrenaline and this effect was independent of concentration. 3. In the presence of yohimbine, the lower part of the inhibitory-response curve for noradrenaline was slightly but significantly shifted by prazosin. A similar degree of antagonism was observed in the presence of 1 microM phenoxybenzamine. 4. The selective alpha 2 agonists BHT 920 and clonidine reduced, in the same concentration-range (0.01-1 microM), the cardiac response to transmural nerve stimulation in a yohimbine-sensitive fashion. 5. Phenylephrine (0.1-100 microM) and methoxamine (1-300 microM) also induced an inhibitory effect on transmural nerve stimulation. The effect of phenylephrine was antagonized by yohimbine (1 microM) more efficiently than by prazosin (0.5 microM). 6. These results are in keeping with the presence of inhibitory prejunctional alpha 2-adrenoceptors on cardiac sensory nerve endings which modulate the efferent function of capsaicin-sensitive neurones.     

Action of histamine on nerve mediated responses of the guinea-pig ileum

The effect of histamine on the responses of the guinea-pig ileum to stimulation of intramural nerves and to some potential nonadrenergic, noncholinergic (NANC) neurotransmitters was analysed. During sustained tonic histamine contraction, electrical stimulation of all intramural nerves elicited a biphasic response (contraction followed by after-relaxation) and application of ATP and bradykinin caused relaxation of the ileum in contrast to their contractile effect on basal tension. Histamine reduced contractile and augmented relaxatory NANC responses, and prevented capsaicin from producing any contractile effect and from significantly influencing the NANC contractions. The present results suggest that, besides its direct effect, histamine activates intramural nerve fibres, mainly the sensory ones, and unmasks NANC relaxation thus modifying the mechanical activity.     

5-HT mediated GABA excitatory responses in the guinea-pig proximal ileum

GABA (3--100 microM) and 5-HT (0.03--30 microM) caused concentration-dependent transient contractions of the longitudinal muscle of the guinea-pig ileum. The contractile response to GABA was antagonized by hyoscine (2.2 microM). TTX (0.7 microM), bicuculline (3 microM), furosemide (25 microM) and desensitization to GABA itself, while hexamethonium (20 microM) and methysergide (20 microM) were without effect. The contractile response to 5-HT was antagonized by hyoscine (2.2 microM), TTX (0.7 microM) and desensitization to 5-HT itself and was unaffected by bicuculline (10 microM), hexamethonium (20 microM), furosemide (25 microM) and methysergide (20 microM). A desensitization procedure that caused a 84.7-fold increase in the 5-HT EC50 also resulted in a 74.1-fold increase of the GABA EC50. Desensitization to GABA caused a reduction of 5-HT induced response but only in preparations desensitized by high (50 microM) concentrations of GABA. The results indicate that GABA-induced contractions in the guinea-pig ileum are mediated by activation of cholinergic motor neurones. This effect appears to be mediated by interneuronal release of 5-HT rather than by a direct stimulatory action of GABA on the effector neurones.     

Alpha-adrenoceptor subtypes.

Different studies have led to our present knowledge of the membrane receptors responsible for mediating the responses to the endogenous catecholamines. These receptors were initially differentiated into alpha - and beta-adrenoceptors. Alpha-adrenoceptors mediate most excitatory functions, and were in turn differentiated in the 1970s into alpha(1)- and alpha(2)-adrenoceptors. The alpha(1)-adrenoceptor type usually mediates responses in the effector organ. The alpha(2)-adrenoceptor type is located presynaptically and regulates the release of the neurotransmitter but it is also present in postsynaptical locations. Both alpha-adrenoceptors are important for the control of vascular tone, but we now know that neither alpha(1)- nor alpha(2)-adrenoceptors constitute homogeneous groups. Each alpha-adrenoceptor type can be subdivided into different subtypes and in this review we have turned our attention to these. The alpha(1)- and the alpha(2)-adrenoceptor subtypes were previously defined pharmacologically by functional and binding studies, and later they were also isolated and identified using cloning methods. In fact, the study of alpha-adrenoceptors was revolutionized by the techniques of molecular biology which permitted us to establish the present classification. The present classification of alpha(1)-adrenoceptors stands as follows: alpha(1A)-adrenoceptor subtype (cloned alpha(1c) and redesignated alpha(1a/c)), alpha(1B)-adrenoceptor subtype (cloned alpha(1b)) and alpha(1D)-adrenoceptor subtype (cloned alpha(1d) and redesignated alpha(1a/d)). It has not been easy to establish the distribution of these alpha(1)-adrenoceptor subtypes in the various organs and tissues, or to define the functional response mediated by each one in the different species studied. Nevertheless it seems that the alpha(1A)-adrenoceptor subtype is more implicated in the maintenance of vascular basal tone and of arterial blood pressure in conscious animals, and the alpha(1B)-adrenoceptor subtype participates more in responses to exogenous agonists. It has also been observed that the expression of the alpha(1B)-adrenoceptor subtype can be modified in pathological situations and particular attention has been paid to the regulation of expression of this receptor. The present classification of alpha(2)-adrenoceptors stands as follows: alpha(2A/D)-adrenoceptor subtype (today it is accepted that the alpha(2A)-adrenoceptor subtype and the alpha(2D)-adrenoceptor subtype are the same receptor but they were identified in different species: the alpha(2A) in human and the alpha(2D) in rat); alpha(2B)-adrenoceptor subtype (cloned alpha(2b)) and alpha(2C)-adrenoceptor subtype (cloned alpha(2c)). Today we know that the alpha(2A/D)- and alpha(2B)-adrenoceptor subtypes in particular control arterial contraction, and that the alpha(2C)-adrenoceptor subtype is responsible above all for venous vasoconstriction. We also know that the alpha(2 A/D)-adrenoceptor subtype fundamentally mediates the central effects of the alpha(2)-adrenoceptor agonists. Despite the validity of the above-mentioned classification of the alpha(1)- and alpha(2)-adrenoceptors, it seems clear that the contractions of a large number of tissues including smooth muscle are mediated by more than one alpha-adrenoceptor subtype. Moreover, few ligands recognise only one alpha-adrenoceptor subtype and the lack of specifity in the different drugs for each one limits their administration in vivo and their therapeutic use.     

Sympathetic co-transmission to the cauda epididymis of the rat: characterization of postjunctional adrenoceptors and purinoceptors.

1. Electrical field stimulation (10 Hz, 60 V, 1 ms, for 10 s) produced monophasic contractions of isolated preparations of rat cauda epididymis which could be abolished by guanethidine, and attenuated by prazosin and alpha, beta-methylene ATP. 2. The rank order of potency of adrenoceptor agonists in causing contraction of the preparation in the presence of the neuronal uptake blocker, nisoxetine (0.1 microM) was: adrenaline greater than or equal to phenylephrine greater than or equal to noradrenaline greater than clonidine greater than methoxamine greater than metaraminol greater than dopamine greater than or equal to isoprenaline greater than xylazine. 3. Responses to the agonists were blocked by prazosin but not by propranolol or idazoxan. 4. The rank order of potency of purinoceptor agonists in causing contraction of the cauda epididymis was: alpha,beta-methylene ATP greater than beta,gamma-methylene ATP greater than or equal to 2-methylthio ATP greater than ATP greater than ADP. AMP and adenosine did not cause contractions. 5. Contractile responses to the purine nucleotide analogues were blocked by repeated application of alpha,beta-methylene ATP. 6. It is concluded that both ATP and noradrenaline may act as co-transmitters in the sympathetic nerves supplying the smooth muscle of the rat cauda epididymis, and that alpha 1-adrenoceptors and P2x-purinoceptors are present postjunctionally.     

Supersensitivity to noradrenaline in preparations of rat cauda epididymis after vasectomy

Preparations of cauda epididymides were taken from rats unilaterally vasectomised by medial transection of the vas deferens. Responses of preparations from the operated side to field stimulation (10 pulses, 70 V, 1 ms, 0.1-20 Hz) declined in parallel with decreases in catecholamine fluorescence. There were leftward shifts in the mean cumulative concentration-response curves to noradrenaline on vasectomised cauda epididymides of 5-, 10-, and 12-fold at days 2, 7 and 28, respectively compared to unoperated cauda epididymides following vasectomy. Nisoxetine (0.1 mumol/l) enhanced the potency of noradrenaline upon unoperated but not upon vasectomised segments. There were leftward shifts of 7- and 8-fold in the mean cumulative concentration-response curves to acetylcholine in vasectomised cauda epididymides at days 2 and 7, respectively, following surgery. Responses to methoxamine and carbachol were unaffected by vasectomy. Thus neurotransmission to the smooth muscle of the rat cauda epididymis resembles that to the vas deferens, in that vasectomy results in the development of prejunctional supersensitivity to noradrenaline and acetylcholine.     

Pharmacological characteristics of the postsynaptically mediated contractile responses of guinea-pig ileum to long-lasting electrical field stimulation

The contractile responses of the longitudinal smooth muscle layer of the isolated guinea-pig ileum which were elicited by long-lasting (40 sec train duration) electrical field stimulation (0.8 msec, 20 V), applied at a frequency of either 5 or 30 Hz, comprised an initial phasic component followed by a secondary tonic contraction, were studied against the background of postsynaptically-acting receptor antagonists. Atropine and apamin reduced both components of the responses while prazosin produced no change. Propranolol induced a slight reduction, decreasing mainly the responses evoked by stimulation at a frequency of 5 Hz. The simultaneous application of cholinoceptor and adrenoceptor blockers revealed a non-cholinergic, non-adrenergic component of the responses. The putative prostaglandin antagonist, SC 19220 was found to reduce mainly the tonic component of the non-cholinergic, non-adrenergic contractions evoked by stimulation at both frequencies used. These results demonstrated that the two-component contractile responses of the guinea pig ileum to long-lasting electrical stimulation were due to the release of more than one neurotransmitter and/or spasmogenic substance. It is concluded that the initial phasic component was evoked by acetylcholine and by a non-cholinergic, non-adrenergic neurotransmitter, while the tonic component was maintained predominantly by prostaglandins released during stimulation.     

Gi-Protein alpha-subunit mRNA antisense oligonucleotide inhibition of Gi-coupled receptor contractile activity in the epididymis of the guinea-pig.

We have used a reversible permeabilization method to facilitate the entry of Gialpha1, 2 and 3 G-protein subunit mRNA antisense or mismatch oligonucleotides into intact tissue, to investigate the G-protein alpha-subunit coupling of alpha2-adrenoceptors, neuropeptide Y (NPY) Y1, and A1 adenosine receptors in preparations of the epididymis of the guinea-pig. The alpha2-adrenoceptor agonist, xylazine, elicited concentration dependent contractions from preparations of phenylephrine (3 microM)-stimulated epididymis (pEC50 value 6.52+/-0.39, maximum response 236+/-41 mg force). Compared to respective mismatch controls the incubation of preparations with Gialpha2, but not with Gialpha1 or Gialpha3 mRNA antisense oligonucleotides (30 microM) reduced the maximal xylazine-potentiation of phenylephrine (3 microM)-stimulated contractility (to 51+/-12% of Gialpha2 mismatch control). The oligonucleotide incubations had no effect upon the pEC50 values of xylazine. The A1 adenosine receptor agonist, cyclopentyladenosine (CPA) elicited concentration dependent contractions from preparations of phenylephrine (3 microM)-stimulated epididymis (pEC50 value 7.66+/-0.57, maximum response 208+/-54 mg force). Incubation of preparations of epididymis with Gialpha1, but neither Gialpha2 nor Gialpha3 antisense oligonucleotides reduced the maximal CPA-potentiation of phenylephrine (3 microM)-stimulated contractions (to 55+/-17% of Gialpha1 mismatch control), pEC50 values were not affected. The incubation of preparations with Gialpha2 antisense mRNA oligonucleotides reduced the maximal NPY-potentiation of phenylephrine (3 microM)-stimulated contractions (to 62+/-15% of Gialpha mismatch control). Compared with Gialpha2 mismatch controls, the incubation of preparations with Gialpha1 and Gialpha3 oligonucleotides also reduced the NPY-potentiation of phenylephrine (3 microM)-stimulated contractions. These studies indicate that, in the guinea-pig epididymis, alpha2-adrenoceptors and A1 adenosine receptors preferentially couple to effectors through Gialpha2 and Gialpha1 subunits respectively. In contrast NPY receptors may elicit effects through either Gialpha1, 2 or 3 subunits.     

Receptors mediating tachykinin-induced contractile responses in guinea-pig trachea.

1. The classification of tachykinin receptors in the guinea-pig trachea has been investigated. This was of interest because, from previous studies, it was not clear whether the guinea-pig trachea contains either a mixture of NK1 and NK2 receptors or, alternatively, a single type of novel tachykinin receptor. 2. In the present study, the guinea-pig trachea was contracted by tachykinin agonists selective for NK1 receptors (substance P methylester (SPOMe) and GR73632) or NK2 receptors (GR64349) but not NK3 receptors (senktide). 3. Against SPOMe and GR73632, the NK1 antagonist, GR71251, behaved as a reversible competitive antagonist having apparent affinity (pKB 7.05 vs SPOMe) consistent with action at NK1 receptors. GR71251 (3 microM) did not antagonize responses to GR64349. 4. The NK2 antagonists L-659,877 and Ac-Leu-Asp-Gln-Trp-Phe-Gly-NH2 (R396) antagonized GR64349 although only R396 appeared to behave competitively (pKB 5.73). Neither L-659,877 (30 microM) nor R396 (30 microM) blocked responses to SPOMe. 5. For L-659,877 and R396, comparison was made between activity in guinea-pig trachea and in preparations known to contain tachykinin receptors predominantly of the NK2 type. In the rabbit trachea, both L-659,877 and R396 had effects similar to those in guinea-pig trachea. In contrast, in the rat colon muscularis mucosae, both L-659,877 and R396 appeared to behave competitively with pKB values against GR64349 of 7.83 and 6.90 respectively. 6. It is concluded that in guinea-pig trachea, contractile responses can be induced by activation of both NK1 and NK2 receptors. The present data are discussed with reference to the proposed existence of subtypes of the NK2 receptor.     

Alpha-adrenoceptor responsiveness in the aged rat

The effects of ageing on vascular alpha 1- and alpha 2-adrenoceptors were examined using anaesthetised and pithed young (3-7 months) and old (21-24 months) Sprague-Dawley rats. In pithed animals, the pressor and cardioinhibitory effects of the alpha 2-adrenoceptor agonist xylazine were significantly reduced in old animals (8- and 6-fold shift), but the pressor effects of the alpha 1-adrenoceptor agonist amidephrine were not significantly altered by ageing. In anaesthetised rats, the pressor response to the mixed alpha-adrenoceptor agonist noradrenaline (NA) was not significantly altered, and the pressor potency of the alpha 1-adrenoceptor agonist amidephrine was only slightly reduced (1.7-fold shift) in old animals. In the presence of cocaine (1 mg kg-1) the pressor potency of NA was markedly reduced (13-fold shift) in old animals. In the presence of prazosin (1 mg kg-1) to eliminate alpha 1-adrenoceptor-mediated responses, the pressor potency of NA was markedly reduced in old as animals as compared to young animals (16-fold shift). The neuronal uptake blocker cocaine (1 mg kg-1) significantly potentiated the pressor response to NA only in young. In summary, we have found a reduced alpha 2-adrenoceptor-mediated pressor and cardioinhibitory responsiveness and a reduced neuronal uptake of NA in old animals with little change in alpha 1-adrenoceptor-mediated vascular responsiveness.     

The alpha adrenergic receptor mediated increase in guinea-pig liver glycogenolysis.

Amidephrine, a selective α-adrenergic receptor agonist, and isoprenaline, a selective β-receptor agonist, each produced comparable, dose related, increases in the glycogen phosphorylase activity of guinea-pig liver slices, while only isoprenaline produced a statistically significant increase in cyclic AMP levels. These effects were obtained with agonist concentrations which produced similar increases in the rate of glucose release. Although the tissue was only exposed to the drugs for 2 min. it is not thought likely that an earlier peak in cyclic AMP, caused by amidephrine, remained undetected, as the α-agonist did not stimulate adenylate cyclase in a membrane preparation from guinea-pig liver. The effect of amidephrine on phosphorylase activity was abolished by phentolamine at a concentration which did not affect the response to isoprenaline. It is concluded that α-receptor stimulation is as effective as β-receptor stimulation in increasing hepatic glycogenolysis, but that the α-mediated effects do not involve cyclic AMP. The possibility that α effects result from changes in phosphorylase kinase or phosphatase activity brought about by cellular calcium re-distribution is discussed.     

Effects of dietary selenium (SE) on morphology of testis and cauda epididymis in rats

Selenium is an essential micronutrient for animals. To determine whether its excess in diet induces morphological changes within the male reproductive system, a detailed qualitative and quantitative evaluation of the changes in the histology of the testis and cauda epididymis was undertaken in male rats. Adult male albino rats were fed 6 and 8 ppm Se in diet for 6 and 9 weeks. Each male consuming 6 ppm Se was mated with two untreated females, their offsprings were allowed to mature upto 12 weeks of age. The testes and cauda epididymes of male rats were prepared for light microscopy. Excess of dietary Se caused dose-time-dependent reduction in body weight and reproductive organ weights but increase in number of morphologically abnormal spermatozoa. Histopathological studies of the testes and cauda epididymis have revealed that Se-rich diets cause dose-time-dependent reduction in tubular diameter, epithelial height, number of spermatogenic cells and disintegration of cellular associations in the seminiferous tubules of testes along with reduction in the diameter of cauda epididymal tubules and pseudostratification of their epithelial lining. Progeny (feeding on normal diet) of paternally treated rats has shown retarded growth.     

Anti-inflammatory drug actions on allergic responses in guinea-pig skin.

Five non-steroidal anti-inflammatory drugs (indomethacin, naproxen, meclofenamic acid, feprazone and phenylbutazone: NSAIDs) and three glucocorticosteroids (dexamethasone, hydrocortisone and prednisolone) have been tested as local inhibitors of increased vascular permeability in guinea-pig skin. Lesions were induced by histamine or by antigen to evoke type I (passive cutaneous anaphylaxis), type III (reverse passive Arthus) and type IV (delayed hypersensitivity) allergic reactions. NSAIDs and glucocorticosteroids caused either weak, inconsistent inhibition or slight, high-dose inhibition of the response to histamine. None of the drugs tested showed significant inhibition of the type IV response. The NSAIDs caused dose-related inhibition of both type I and type III responses whereas glucocorticosteroids were ineffective. Maximum inhibition with the NSAIDs was never greater than 50--60% Feprazone, meclofenamic acid and indomethacin were the most potent inhibitors of histamine, PCA and Arthus responses respectively. The possible significance of the effects of these anti-inflammatory agents on vascular permeability is discussed.     

Effects of BRL 38227 on neurally-mediated responses in the guinea-pig isolated bronchus.

1. In guinea-pig isolated bronchus treated with indomethacin (2.8 microM), electrical field stimulation (EFS; 10 Hz, 0.5 ms, 60-70 V, for 10 s) evoked a tetrodotoxin (3 microM)-sensitive, biphasic contraction comprising a rapid, atropine (1 microM)-sensitive cholinergic response succeeded by a slowly developing, capsaicin (10 microM)-sensitive, non-adrenergic, non-cholinergic excitatory (NANCe) response. 2. BRL 38227 (0.3-3 microM), salmeterol (0.003-3 microM) and ketotifen (1.0-300 microM) each produced concentration-dependent inhibition of both NANCe and cholinergic responses to EFS in guinea-pig isolated bronchus. 3. Substance P (SP; 1 microM) and neurokinin A (NKA; 0.07 microM) produced contractions equivalent in magnitude to the NANCe response to EFS, which were inhibited by salmeterol (1 microM), but not by BRL 38227 (3 microM) or ketotifen (100 microM). 4. Acetylcholine (ACh; 6 microM) was equi-effective with the electrical activation of cholinergic neurones. BRL 38227 (3 microM) slightly inhibited responses to ACh (6 microM). Salmeterol (1 microM) and ketotifen (100 microM) markedly inhibited responses to ACh (6 microM). 5. In bronchial rings pre-contracted with ACh (100 microM), BRL 38227 (0.1-30 microM), salmeterol (0.001-3 microM) and ketotifen (0.1-100 microM) each produced concentration-dependent relaxation. Unlike ketotifen, BRL 38227 and salmeterol only partially (18.8 +/- 2.1% and 51.8 +/- 3.9% respectively) reversed the ACh-induced contraction. 6. The (+)-analogue of BRL 38227, BRL 38226 (0.3-100 microM), was without effect on responses to EFS and had no effect on the inhibition caused by BRL 38227.(ABSTRACT TRUNCATED AT 250 WORDS)