AUTONOMIC INNERVATION OF THE MUSCLES IN THE WALL OF THE BLADDER AND PROXIMAL URETHRA OF MALE-RATS

Abstract

The autonomic innervation of the muscular coat of the rat urinary bladder and proximal urethra was investigated by EM, partly with serial ultrathin sections. The smooth muscular coat of the body of the bladder was innervated almost exclusively by cholinergic endings. Here, adrenergic endings were very scant. In the inner longitudinal muscle layer of the proximal urethra, 53% of 310 autonomic nerve endings observed in close relation to the smooth muscle cells were adrenergic and the remaining 47% cholinergic. The middle circular smooth muscle layer of the proximal urethra was innervated predominantly by adrenergic endings. In this layer 86% of the total of 335 endings examined were regarded as adrenergic. A similar predominantly adrenergic innervation was noted in the outer longitudinal smooth muscle layer of the proximal urethra. A number of striated muscle fibers arose from the outermost striated muscle layer of the proximal urethra and deeply intruded into the outer and middle smooth muscle layers. These intruding striated muscles also received direct autonomic (mostly adrenergic) innervation. The urethral striated muscles may be under substantial sympathetic control.