Gi‐protein α‐subunit mRNA antisense oligonucleotide inhibition of Gi‐coupled receptor contractile activity in the epididymis of the guinea‐pig

Abstract

We have used a reversible permeabilization method to facilitate the entry of Giα1, 2 and 3 G‐protein subunit mRNA antisense or mismatch oligonucleotides into intact tissue, to investigate the G‐protein α‐subunit coupling of α2‐adrenoceptors, neuropeptide Y (NPY) Y1, and A1 adenosine receptors in preparations of the epididymis of the guinea‐pig. The α2‐adrenoceptor agonist, xylazine, elicited concentration dependent contractions from preparations of phenylephrine (3 μM)‐stimulated epididymis (pEC50 value 6.52±0.39, maximum response 236±41 mg force). Compared to respective mismatch controls the incubation of preparations with Giα2, but not with Giα1 or Giα3 mRNA antisense oligonucleotides (30 μM) reduced the maximal xylazine‐potentiation of phenylephrine (3 μM)‐stimulated contractility (to 51±12% of Giα2 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 μM)‐stimulated epididymis (pEC50 value 7.66±0.57, maximum response 208±54 mg force). Incubation of preparations of epididymis with Giα1, but neither Giα2 nor Giα3 antisense oligonucleotides reduced the maximal CPA‐potentiation of phenylephrine (3 μM)‐stimulated contractions (to 55±17% of Giα1 mismatch control), pEC50 values were not affected. The incubation of preparations with Giα2 antisense mRNA oligonucleotides reduced the maximal NPY‐potentiation of phenylephrine (3 μM)‐stimulated contractions (to 62±15% of Giα mismatch control). Compared with Giα2 mismatch controls, the incubation of preparations with Giα1 and Giα3 oligonucleotides also reduced the NPY‐potentiation of phenylephrine (3 μM)‐stimulated contractions. These studies indicate that, in the guinea‐pig epididymis, α2‐adrenoceptors and A1 adenosine receptors preferentially couple to effectors through Giα2 and Giα1 subunits respectively. In contrast NPY receptors may elicit effects through either Giα1, 2 or 3 subunits. British Journal of Pharmacology (1999) 127, 85–90; doi:10.1038/sj.bjp.0702515

Current models of human prostate contractility

“…99 Previously, we have shown that, in non-prostatic smooth muscle, agents that activate Gi-coupled receptors may not necessarily elicit contractions, but may potentiate the contractile responses to other agents. 23 Thus, cultured cell evidence is quite consistent with the effects of cholinergic agonists in human prostatic tissue and indicates the potential complexity of signalling in the human prostatic stroma. Both oxytocin and vasopressin 42,45 have also been shown to elicit contractions of human prostatic tissues but, as yet, there are no equivalent human cultured prostatic stromal cell data.…”

“…20,21 Electrical field stimulation of nerves within human, rat, guinea-pig, rabbit, pig and dog prostate causes contractions that can be abolished by tetrodotoxin, reduced by guanethidine and blocked by ␣ 1 -adrenoceptor antagonists. 19,[21][22][23] These studies indicate that there are similar mechanisms at play in the prostates of all mammalian species and, therefore, that there may be advantages in using animal prostate models to investigate human prostate function. These advantages include the ready availability of animal tissue and the fact that the tissue obtained from laboratory animals is, by nature, very consistent and, in contrast with human tissue obtained at surgery, complete and free from disease.…”

Neuropeptide Y: the universal soldier

“…In particular, NPY exerts a synergistic effect on Gq-mediated NEinduced responses. This raises a question about the molecular mechanisms involved in the potentiating actions of NPY [119,120]. At least three different mechanisms account for the synergistic effects observed in presence of NPY [121].…”

A1 and A2A adenosine receptor modulation of α1‐adrenoceptor‐mediated contractility in human cultured prostatic stromal cells

“…The endogenous purine adenosine has been shown to play a role in the modulation of various cellular functions including smooth muscle contraction and/or relaxation ( Farmer et al , 1988 ; Haynes et al , 1998a ,1998b; Ford & Broadley, 1999; Haynes et al , 1999 ; Sawmiller et al , 1996 ; Prentice et al , 2002 ; Talukder et al , 2002 ), and K + channel conductance ( Hadjkaddour et al , 1996 ; Gopalakrishnan et al , 1999 ; Haynes, 2000; Marian et al , 2002 ). Although four G‐protein‐coupled adenosine receptors have currently been identified, A 1 , A 2A , A 2B and A 3 ( Fredholm et al , 2000 ; Klotz, 2000; Fredholm et al , 2001 ), the vast majority of functional responses are mediated by the A 1 and A 2A adenosine receptors, coupled to G i and G s , respectively ( Fredholm et al , 2000 ).…”