Innervation of the urinary bladder of the sleepy lizard ( Tracysaurus rugosus)—II. Physiology and pharmacology

Abstract

1. 1. The anatomy, physiology and pharmacology of the innervation of the urinary bladder of the sleepy lizard, Trachysaurus rugosus, have been studied. 2. 2. The lizard bladder is supplied by nerves running with the vesical arteries from the sacral plexus. These nerves always contain excitatory fibres and in about 70 per cent of the preparations examined, inhibitory fibres were also demonstrated. 3. 3. The amplitude of nerve-mediated inhibitory responses increased with frequency of nerve stimulation, until a minimal critical frequency was reached at about 20 pulses/sec. The inhibitory response was abolished by guanethidine and was mimicked by the actions of applied catecholamines. The inhibitory fibres thus appear to be adrenergic. 4. 4. The frequency-response curve for the nerve-mediated contraction showed two peaks (at 20 and 35 pulse/sec respectively at 22°C), suggesting that there are two types of excitatory nerve fibres in the periarterial nerve supply to the bladder. 5. 5. The responses which are optimal at the lower frequencies are probably caused by cholinergic fibres. They are reduced although never completely blocked by atropine, potentiated by eserine and mimicked by contractions caused by applied acetylcholine. 6. 6. The nature of the fibres causing contractions at the higher frequency is not clear. Experiments in which nerve-mediated contractions, partially blocked by antropine, were abolished by guanethidine, and vice versa, suggest that the fibres may be adrenergic. However, the use of adrenaline-blocking agents on this preparation is unreliable because of their non-specific actions. 7. 7. Nerve-mediated contractions were reduced by hexamethonium and by nicotine, suggesting that some of the fibres are stimulated pre-ganglionically. 8. 8. The results are discussed in relation to the innervation of the bladder in other vertebrate classes.