Effect of nonachlazine on adrenergic neurotransmission in the rat vas deferens

The effect of a new antianginal preparation, nonachlazine, on adrenergic neurotransmission in the isolated rat vas deferens was studied by recording contractions of the duct in response to transmural stimulation of postganglionic sympathetic nerves by the electric current or by application of noradrenalin (NA) or BaCl₂. The effect of nonachlazine on the NA content was studied spectrofluorometrically and the ability of the preparation to block the uptake of exogenous NA by the tissues also was investigated. Nonachlazine was found to have a moderate sympatholytic action, which was combined with its spasmolytic effect. Nonachlazine also has a well marked ability to block the reaccumulation of NA in the tissues.     

Evidence against adrenergic motor transmission in the guinea-pig vas deferens

1. Field stimulation of desheathed preparations of guinea-pig vas deferens, treated with a ganglion-blocking agent, has revealed the presence of two tetrodotoxin-susceptible components in the motor response, suggesting the existence of two sets of post-ganglionic motor nerve fibres of different excitability: one set responding maximally to pulses of 0.1-0.4 msec; the other, to pulses of 2 msec. No distinction could be made pharmacologically between the two components.2. Cooling potentiated that component in the twitch-responses which was due to stimulation of the more excitable fibres.3. The sensitivity of the longitudinal muscle to the motor action of noradrenaline was low and was subject to considerable animal variation. But normal responses to post-ganglionic field stimulation were elicited in noradrenaline-insensitive preparations, in which the twitches elicited by 5 pulses could not be matched with noradrenaline, even 100-125 mug/ml.4. In some forty experiments, small doses of noradrenaline inhibited the twitch-responses evoked by either set of motor fibres. This inhibition differed from that produced by isoprenaline in two respects. Firstly, propranolol did not antagonize the noradrenaline inhibition, thus excluding an action on beta-adrenoceptors; and secondly, noradrenaline did not depress contractions elicited by muscarine or by 5-methylfurmethide.5. Phenoxybenzamine, 10(-6) g/ml., produced a thousandfold reduction in the sensitivity of the muscle to the motor action of noradrenaline, without any decrease in the height of the twitches elicited by 0.1 or 1 msec pulses.6. The twitch-responses were not affected by combined alpha + beta adrenoceptor blockade with phentolamine and propranolol.7. Tyramine, amphetamine, tranylcypromine and prostaglandin E(2) inhibited the twitches but potentiated the contractile effect of noradrenaline.8. The twitch-responses and their inhibition by noradrenaline were present in preparations taken from reserpinized animals.9. Although the twitch-responses could be paralysed by bretylium or guanethidine, the foregoing results excluded adrenergic transmission at the motor endings. Cholinergic transmission was also excluded by negative findings with anticholinesterases, atropine, nicotine and (+)-tubocurarine.10. Motor transmission by histamine, 5-hydroxytryptamine, gamma-aminobutyric acid or ATP was also excluded.     

Structure activity relations for inhibition of neurotransmission in rat vas deferens by adenosine

Adenosine inhibits the isometric contractions of the rat vas deferens in response to field stimulation in vitro by presynaptic inhibition of transmitter release. In the present study the structure activity relations for the inhibition of neurotramsmission in the rat vas deferens by adenosine were examined. Adenosine and adenosine-N¹-oxide were the most potent inhibitors studied. 6-Methylaminopurine riboside, 6-hydroxylaminopurine riboside, 5′-deoxyadenosine and 5′-nitroadenosine were slightly less potent inhibitors. The common structural requirements for activity include a primary or secondary amine function at C₆ of the purine ring with little tolerance for major steric changes or substitutions on the sugar moiety. None of the analogues studied prevented the presynaptic inhibitory action of adenosine.     

Bradykinin facilitates the purinergic motor component of the rat bladder neurotransmission

The motor activity of the rat bladder elicited by transmural electrical stimulation was abolished in the presence of 200 nM tetrodotoxin but not of 1 microM atropine plus 3.4 microM guanethidine. Tissue preincubation with 20 microM, alpha, beta-methylene ATP reduced but did not obliterate the electrically-induced motor effect. Bradykinin (BK) caused a short-lasting motor response while it potentiated, in a concentration-dependent fashion, the 0.15-5 Hz-induced muscle twitching. The facilitatory action of the peptide lasted for at least 5 min and was blocked by the BK-B2 receptor antagonist D-Arg0 [Hyp3, Thi5,8, D-Phe7]-BK. The motor response caused by the exogenous application of adenosine 5'-triphosphate (ATP) was almost immediate and lasted less than 30 s; it was also potentiated by BK-B2 receptor activation, an effect that was reduced in a concentration-dependent manner by pretreatment with the BK-receptor antagonist.     

Gross and histological variations along the length of the rat vas deferens

The gross morphology of the vas deferens of the rat and the changes that occur along its length are reported. It is shown that the organ can be divided into proximal, distal and terminal portions. Each portion is histologically unique and is situated in a different part of the body. The differences are discussed in relation to the function of the organ and their possible role in the consequences of vasectomy.     

Presynaptic inhibitory actions of adenine nucleotides and adenosine on neurotransmission in the rat vas deferens.

Adenine nucleotides and adenosine inhibited the isometric contractions of the rat vas deferens in vitro in response to field stimulation but had no effect on the responses to exogenous noradrenaline. The inhibitions were potentiated by dipyridamole and compound 555, antagonized by theophylline and unchanged by indomethacin, 2-2′-pyridylistogen, phenoxybenzamine and atropine. Adenosine and adenosine 5′-triphosphate inhibited the release of [³H]noradrenaline produced by field stimulation.These results indicate that adenine nucleotides, probably acting via the common metabolite adenosine, inhibit adrenergic neurotransmission at a presynaptic site. Their antagonism by theophylline suggests that a presynaptic ‘purinergic’ receptor system could be involved.     

Reserpine-induced potentiation of the inhibitory action of neuropeptide Y on the rat vas deferens neurotransmission

The inhibitory action of neuropeptide Y (NPY) on the muscular activity of the prostatic end of the rat vas deferens elicited by transmural electrical stimulation was examined in control and in reserpinized rats. Pretreatment with 1 mg/kg reserpine for 48 h induced a 6-fold increase in NPY potency. Likewise, the potency of clonidine to inhibit the electrically induced muscular activity or noradrenaline to contract the ductus musculature was also potentiated. It is hypothesized that reserpine via a denervation super-sensitivity-like process increases the density of the NPY receptors. The functional significance of NPY in the motor activity of the vas deferens is discussed.     

Further evidence for adrenergic transmission in the human vas deferens.

1. Isolated portions of human vas deferens responded to field stimulation of the intramural nerve fibres or to exogenously applied noradrenaline with rhythmical contractions of both longitudinal and circular muscle layers. 2. In guinea-pig and rabbit vas deferens field stimulation produced an initial rapid 'twitch' response which was not found with human vasa. 3. Responses of the human vas to field stimulation were depressed by the alpha-adrenoceptor blocking agents phentolamine and yohimbine. 4. It is concluded that the motor innervation of the human vas deferens is adrenergic and the relevance of this to the physiological operation of the tissue is discussed.     

Disappearance of small vesicles from adrenergic nerve endings in the rat vas deferens caused by red back spider venom

Summary As well as causing the release of acetylcholine and the disappearance of synaptic vesicles from somatic nerve endingsLatrodectus venom also causes the release of noradrenaline and the disappearance of small vesicles from adrenergic nerve endings. The large granular vesicles of the adrenergic endings are less sensitive to the action of the venom.     

Subcellular distribution of adenylate cyclase and cyclic adenosine monophosphate phosphodiesterase in rat and guinea-pig vas deferens

Cyclic adenosine 3′:5′-monophosphate (cyclic AMP) is assumed to play a role in catecholamine synthesis and release. In order to determine if cyclic AMP metabolism at the level of the storage granule is important in this respect the subcellular distribution of adenylate cyclase and cyclic AMP phosphodiesterase was determined in vas deferens from normal rats, castrated rats and castrated guinea-pigs. The phosphodiesterase activity was mainly found in the soluble fractions, while the adenylate cyclase was associated with sedimentable material. When vas deferens homogenates from both intact and castrated rats were subjected to sucrose density gradient centrifugation the main part of the adenylate cyclase activity was found associated with membrane fragments at 0.5–0.6 m sucrose. The distribution of adenylate cyclase activity in the density gradient parallelled that of 5′-nucleotidase, but was different from that of noradrenaline. Also in the guinea-pig, adenylate cyclase tended to have a different distribution from that of noradrenaline.The adenylate cyclase activity in, all fractions was stimulated by fluoride and guanosine triphosphate. Noradrenaline, prostaglandin E₂, 2-chloroadenosine and phenylisopropyladenosine stimulated adenyl cyclase activity in nuclear and mitochondrial fractions, but only to a small extent, if at all, in the fractions collected from the density gradient.The results do not indicate that adenylate cyclase activity in vas deferens homogenates is associated with catecholamine storage vesicles. Hence, cyclic AMP metabolism at the level of the storage granule is probably not involved in transmitter turnover.     

Effects of neuropeptide Y (NPY) on mechanical activity and neurotransmission in the heart, vas deferens and urinary bladder of the guinea-pig

The effects of preincubation for 10 min with synthetic porcine neuropeptide Y (NPY) on muscle tone and autonomic transmission in the guinea-pig right atrium, vas deferens, urinary bladder, portal vein and trachea were analysed in vitro. NPY induced a metoprolol-resistant, long-lasting, positive inotropic and chronotropic effect per se in the spontaneously beating right atrium. Furthermore, NPY caused a reversible inhibition of both the metoprolol and atropine-sensitive auricle responses to field stimulation (2 Hz or 4 Hz for 2 s) without affecting the response to exogenous noradrenaline (NA) or acetylcholine (ACh). NPY did not induce any contraction of the vas deferens, but inhibited both the rapid twitch response and the sustained tonic contraction induced by field stimulation. The NPY-induced inhibition of the tonic contraction was more long-lasting than that of the twitch response. The tonic contraction was blocked by phentolamine and the twitch response by alpha-, beta-methylene ATP tachyphylaxis. NPY did not inhibit the contractile effects of NA, ATP or alpha-, beta-methylene ATP. NPY also induced a reversible reduction of the non-cholinergic, non-adrenergic contractile response to field stimulation of the urinary bladder. In the portal vein, NPY (up to 5 X 10(-7) M) did not inhibit the spontaneous motility or the phentolamine-sensitive contractile responses to field stimulation and NA. The atropine-sensitive contraction of the trachea or the non-adrenergic, non-cholinergic relaxation induced by field stimulation were not significantly influenced by NPY in doses up to 5 X 10(-7) M.(ABSTRACT TRUNCATED AT 250 WORDS)     

An analysis of the anatomical basis for the mechanical response to motor nerve stimulation of the rat vas deferens

1. An anatomical basis was sought for the biphasic motor nerve response of the rat vas deferens. The motor nerve pathway to the tissue was stimulated at different points between the vertebral outflow and the intramural fibres, in the pithed rat and in isolated tissues, to examine the possibility of two anatomically separate groups of neurones. Different preparations of the isolated tissue were devised to detect whether different groups of smooth muscle fibres contributed to the two phases.2. The fibres mediating both phases of the response arose from the upper lumbar vertebral outflows. Both phases were elicited by pre- or post-ganglionic stimulation and could be depressed by hexamethonium. In the pithed rat or with hypogastric nerve stimulation in the isolated tissue, however, the initial ;twitch' phase was relatively resistant to such blockade.3. When the rat vas deferens was perfused through the lumen in situ or in vitro, the perfusion pressure response to motor nerve stimulation exhibited two phases similar to those of the longitudinal contractile response.4. Isolated rat vasa were bisected into portions, each of which was stimulated and longitudinal tension was recorded. The proportions of the two phases of the response varied along the length of the tissue. At the prostatic end the total response was relatively weak with a dominant ;twitch' and at the epididymal end the two phases were comparable in magnitude. The distribution of adrenergic nerve terminals within the muscle layers also varied along the length of the rat vas deferens.5. The effects of drugs were investigated on the motor responses of the above preparations. The ;twitch' phase was relatively susceptible to blockade by reserpine and lysergic acid diethylamide and the ;secondary' phase to phentolamine with both equally sensitive to guanethidine. Each phase had similar susceptibilities to blockade irrespective of which part of the tissue was involved.6. It was concluded that two types of nerve-muscle transmission may be involved in the rat vas deferens with the proportion of each varying along the length of the tissue but both displaying pharmacological characteristics of adrenergic fibres.     

Postnatal androgen deprivation dissociates the development of smooth muscle innervation from functional neurotransmission in mouse vas deferens

The pelvic autonomic nervous system is a target for circulating androgens in adults, with androgen exposure or deprivation affecting the structure and function of urogenital tract innervation. However, the critical period for androgen exposure to initially establish pelvic autonomic neuromuscular transmission has not been determined. We have examined the sympathetic innervation of the vas deferens in hypogonadal ( hpg ) mice that are deprived of androgens after birth but undergo normal prenatal sexual differentiation and remain androgen responsive throughout life. In vasa deferentia from hpg mice, purinergic excitatory junction potentials and contractions could not be elicited by electrical stimulation and P2X₁ purinoceptors could not be demonstrated by immunofluorescence. Moreover, a novel inhibitory nitrergic transmission developed. Administering testosterone to adult hpg mice restored purinergic excitatory transmission and P2X₁ purinoceptor immunofluorescence, and nitrergic inhibitory transmission was lost. Despite the deficit in excitatory neurotransmission in hpg mice, their vasa deferentia were innervated by numerous noradrenergic axons and pelvic ganglia appeared normal. In addition, noradrenergic contractions could be elicited by electrical stimulation. This study has revealed that postnatal androgen exposure has a profound effect on the development of excitatory transmission in vas deferens smooth muscle, primarily by a postjunctional action, but is not essential for development of the structural innervation of this organ. Our results also indicate that there is no postnatal critical period for androgen exposure to establish neuroeffector transmission and that postnatal androgen exposure can be delayed until adulthood, with little consequence for establishment of normal sympathetic neurotransmission.     

Sympathetic efferent pathways projecting bilaterally to the vas deferens in the rat

ABSTRACT Background: The laterality of the signals passing through the splanchnic nerves to the vas deferens has not been well studied. Methods: The present study was designed to determine the bilateral distribution of sympathetic nerves to the rat vasa deferentia by measuring intravasal pressure (VP) responses to electrical stimulation of left lumbar splanchnic nerves (LSN) following consecutive transections of more distal nerves. Results: L₂-L₆ LSN stimulation increased VP bilaterally. Left VP responses decreased slightly (<20%) after section of the right hypogastric nerve (HGN) and then were abolished by subsequent section of branches (B-M-APG) between the left major pelvic (MPG) and accessory pelvic ganglia (APG). Left VP responses were decreased by >80% after section of left HGN, not changed further by subsequent section of commissural branches (CB-MPG) between the MPG, and completely eliminated by section of commissural branches between the APG (CB-APG). Right VP responses were decreased slightly (<20%) by section of the left HGN and then abolished by section of the right B-M-APG. These responses were also decreased by >70% by section of right HGN, not changed by section of CB-MPG, but then completely eliminated by section of CB-APG. Conclusions: These results indicate that the left lumbar sympathetic pathway to the vas deferens is distributed bilaterally and exhibits two crossing points at the level of the inferior mesenteric ganglion and APG. Anat. Rec. 248:291-299, 1997. © 1997 Wiley-Liss, Inc.