Modulation of α₁‐adrenoceptors and functional consequences in the bisected rat vas deferens following chronic inhibition of neuronal noradrenaline uptake

Abstract

reduction in density of a,-adrenoceptors was higher in the epididymal than the prostatic half. Desipramine reduced the B. only in the epididymal portion. 5 These results indicate that differential regulation of ax-adrenoceptors in either portion of the rat vas deferens could result from a greater degree of activation of these receptors in the epididymal half after chronic inhibition of neuronal noradrenaline uptake. The different functional consequences of the loss of al-adrenoceptors in each portion seems to be explained on the basis of a different relationship between the occupancy of the receptor and the response elicited.

Different α 1 -adrenoceptor-induced inositol phosphate formation in the two portions of rat vas deferens

“…Our experiments also demonstrate a greater pEC 50 value for the epididymal half, suggesting that this portion shows a significant enhancement in agonist potency. This finding is in agreement with our previous results in contractile responses (Sallés and Badia 1993) where, in the presence of 0.1 µM desipramine to block noradrenaline neuronal uptake, the pEC 50 value in the epididymal portion was 6.31±0.04, whereas the pEC 50 value in the prostatic portion was 5.31±0.05 (P<0.001, n=10). These differences in the sensitivity to noradrenaline were also reported by Boselli et al (1997) and Sneddon and Machaly (1992).…”

“…Few studies have been made to compare functional and second messenger responses in the two portions of rat vas deferens. In an attempt to relate these results with data on contraction studies, we have reviewed a previous work carried out in our lab (Sallés and Badia 1993). In this paper the maximum contraction (E max ) elicited with noradrenaline was higher in the epididymal (E max : 2037±45 mg tension) than in the prostatic portion (E max : 630±25 mg tension; P<0.0001, n=10).…”

Alpha-1 adrenoceptor subtypes (high, low) in human benign prostatic hypertrophy tissue according to the affinities for prazosin

“…However, our data showed that neither ␣ 1 blocker nor antiandrogen did alter the conditions of the ␣ 1 receptor except for slight change in the relative density of ␣ 1 -adrenoceptor subtypes. It has been reported that the long-term treatment with inhibitors of neuronal norepinephrine uptake leads to ␣ 1 -adrenoceptor downregulation in the epididymal portion of rat ductus deferens, probably due to an increased level of norepinephrine in the vicinity of its receptors [27]. However, the degree of downregulation in the prostatic portion differs due to the types of inhibitors.…”

Use of the operational model of agonism and [3H]prazosin binding to assess altered responsiveness of α1-adrenoceptors in the vas deferens of spontaneously hypertensive rat

“…Crude membrane preparations were obtained according to Sallés and Badia (1993). Briefly, the epididymal portions of the vas deferens from three rats were pooled, placed in 10 ml of ice cold 50 mM Tris-HCl buffer pH 7.5 and homogenized with a Polytron homogenizer (setting 10, 2 × 15 s).…”