Rabbit urethra

On the other hand, an in vitro study using the rabbit bladder membrane revealed that ns increased rapidly during the pre-loading period for the first 60 min, whereas nk remained constant as seen in Fig. 25 [87], but an in vivo study demonstrated that the friction force increased after cytoscopy of the rabbit urethra. The result is shown in Fig. 26. In this study, ten male rabbits were used for imitating cystoscope operation. One of stainless-steel pipes... 

Andersson et al. (1992) used transversal strips from the middle and upper part of rabbit urethra to study the involvement of nitric oxide in the electrically-induced, nerve-mediated relaxation. 

Andersson KE, Mattiasson A, Sjogren S (1983) Electrically induced relaxation of the noradrenaline contracted isolated urethra from rabbit and man. J Urol 129 210-214 Andersson KE, Pascual AG, Persson K et al. (1992) Electrically-induced, nerve-mediated relaxation of rabbit urethra involves nitric oxide. J Urol 147 253-259 Angelico P, Guameri L, Fredella B, Testa R (1992) In vivo effects of different antispasmodic drugs on the rat bladder contractions induced by topically applied KC1.1 Pharmacol Meth 27 33-39... 

Nishi K, Latifpour J, Saito M, Foster HE Jr, Yoshida M, Weiss RM. Characterization, localization and distribution of a, adrenoceptor subtype in male rabbit urethra. J Urol 1998 160 196-205. 

Affinity of selected Oj-AR antagonists for the recombinant animal a,-AR subtypes (pKi= -log,, nM) and functional affinity for the Oj-ARs of vascular and lower urinary tract tissues (pKb= -logj Kb, nM, for inhibition of NA-induced contraction). R.A.= rat aorta RB.A.= rabbit aorta RB.U.= rabbit urethra H.P.=human prostate. The in vivo effects after i.v. administration in the dog model are also listed. Data represent the doses (pg/kg) active in inhibiting by 50% the urethral contractions induced by NA (UP), the doses active in lowering diastolic blood pressure (DBP) by 25%, and the ratio between them. The ratios between the in vitro potency (Kb) on rabbit aorta and urethra are also reported (1/2). 

We investigated organ selectivity of our conqtounds by utilizing, in addition to rabbit urethra, rabbit aorta which is reported to be dependent on 0, - and a,g-AR population [8],... 

The classification of this tissue seems difficult with the data presraited here. In any case, we can observe that among the tested confounds three groups can be considered, based on the results on rabbit urethra and aorta. The quinazoline derivatives prazosin, terazosin and compound 12 show higher affinity for the vascular tissue than for the imethra tamsulosin and... 

Figure 4. Correktion between the binding afSnity (pKi) for the cloned a, -AR and the functional afSnity (pKb) for the aj-adrenoceptors in human prostate (A) and rabbit urethra (B). Dashed line represents the line of identity.

In this modeL prazosin, terazosin and conq>ound 12 proved devoid of selectivity, t hereas tamsulosin and 5-methylurapidil exhibited limited selectivity. SNAP 5089 showed some selectivity but its potency against the urethral contractile response was imexpectedly very low. On the contrary, the novel N-arylpiperazine derivatives (in particular conq>ounds 4 and 7) were endowed with very high potency and selectivity for the lower urinary tract. Interestingly, a good correlation between the in vitro potency on rabbit urethra and the in vivo potency in inhibiting the urethral contractions induced by La. injection of the agonist in the dog was found (R" = 0.925). 

In summary, compounds endowed with high potency in inhibiting contractions of isolated rabbit urethra (a a -AR dependent tissue) showed high potency in inhibiting also the NA induced contraction of the dog urethra in vivo, and in vitro selectivity could be correlated to in vivo selectivity. 

Zygmunt PM, Zygmunt PK, Hogestatt ED, Andersson KE. Effects of omega-conotoxin on adrenergic, cholinergic and NANC neurotransmission in the rabbit urethra and detrusor. Br J Pharmacol 1993 110(4) 1285-90. 

Isotalo, T.M., Nuutine, J.-P., Vaajanent, A. et al. (2006) BiocompatibUity properties of a new braided biodegradable urethral stent a comparison with a biodegradable spiral and a braided metallic stent in the rabbit urethra. BJU International, 97, 856-859. 

Several authors investigated the influence of drugs on isolated parts of the lower urinary tract. Ueda et al. (1984) studied the effects on smooth muscle of the rabbit bladder dome, trigone and proximal urethra. 

Male New Zealand rabbits weighing 2-3 kg are eu-thantized under anesthesia and the abdomen is opened to remove the bladder and the urethra. After excess fat and connective tissue is removed, the bladder and the urethra are dissected into dome, trigone and proximal urethral preparations. All strips are cut transversely being approximately 2-6 mm unstretched. 

Khanna et al. (1977,1981) evaluated the in vitro responses of three segments of rabbit lower urinary tract e.g., the bladder body, the bladder base and the proximal urethra. 

Andersson et al. (1983) studied the electrically induced relaxation of the noradrenaline contracted isolated urethra from rabbit and man. In rabbits, two circular transverse sections, each 4 mm long, were taken from the middle and upper parts of the urethra. Human urethral preparations were obtained from male patients undergoing cysto-urethrectomy en bloc because of bladder cancer. Rings of tissue were taken from the membranous and supra- and infra-collicular parts of the prostatic urethra. 

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