Direct evidence for an angiotensin AT1 receptor type in rat vas deferens

Physiological and pharmacological aspects of the vas deferens-an update

The vas deferens, a muscular conduit conveying spermatozoa from the epididymis to the urethra, has been used as a model tissue for smooth muscle pharmacological and physiological advancements. Many drugs, notably α-adrenergic antagonists, have effects on contractility and thus normal ejaculation, incurring significant side effects for patients that may interfere with compliance. A more thorough understanding of the innervation and neurotransmitter pharmacology of the vas has indicated that this is a highly complex structure and a model for co-transmission at the synapse. Recent models have shown clinical scenarios that alter the vas contraction. This review covers structure, receptors, neurotransmitters, smooth muscle physiology, and clinical implications of the vas deferens.

Mechanisms of adaptive supersensitivity in vas deferens

Adaptive supersensitivity is a phenomenon characteristic of excitable tissues and discloses as a compensatory adjustment of tissue's response to unrelated stimulatory endogenous and exogenous substances after chronic interruption of excitatory neurotransmission. The mechanisms underlying such higher postjunctional sensitivity have been postulated for a variety of cell types. In smooth muscles, especially the vas deferens with its rich sympathetic innervation, the mechanisms responsible for supersensitivity are partly understood and appear to be different from one species to another. The present review provides a general understanding of adaptive supersensitivity and emphasizes early and recent information about the putative mechanisms involved in this phenomenon in rodent vas deferens.

Dual effect of endothelin 1 on angiotensin II-potentiated purinergic neurotransmission in prostatic rat vas deferens

Angiotensin and endothelin are vasoactive peptides with neuromodulatory effect, however their interactions in facilitating neurotransmission are largely unknown. In the present study, effort was made to examine how endothelin 1 modulates angiotensin II-potentiated purinergic neurotransmission in prostatic rat vas deferens. Both peptides facilitated field-stimulated muscle contraction in a concentration-dependent manner with Kd values of 16.97+/-6.47 and 2.46+/-0.83 nM for angiotensin II and endothelin 1, respectively. Hill plot analysis gave Hill constants of 0.91+/-0.15 and 0.97+/-0.26 for angiotensin II and endothelin 1, respectively. Correlation analysis indicated that the extent of potentiation by angiotensin II, but not endothelin 1, was proportional to the basal field-stimulated muscle contraction. In the presence of low concentrations of endothelin 1 (< or = 3 nM), angiotensin II-potentiated field-stimulated contraction was further enhanced by endothelin. However, in the presence of high concentrations of endothelin 1 (> or = 10 nM), a much increased basal field-stimulated contraction was observed, and the addition of angiotensin II did not elicit any further enhancement in the contractile response. Intriguingly, after prolonged exposure of prostatic rat vas deferens to a high concentration of endothelin 1, the addition of angiotensin II induced a refractory response to field-stimulation. Taken together, our result indicated that endothelin 1 augmented angiotensin II-facilitated purinergic neurotransmission in prostatic rat vas deferens at low concentrations, but inhibited gradually at high concentrations.