Maximal Antidiuresis

CHAPTER ONE

Background of Study

Enuresis is a disorder characterized by repeated voiding of urine into the clothes or in bed of persons with a chronological age or developmental level of at least five years that is not due exclusively to the direct physiological effect of a substance or a general medical condition (1). It may be classified into subtypes according to its occurrence during night-time sleep (nocturnal), during waking hours (diurnal) or both and may be described as primary among individuals who have never achieved urinary continence or as secondary among persons developing symptoms after a period of established urinary continence (1). A child who has experienced a minimum 6-month period of continence before the onset of the bedwetting

The hormone also has neurotransmitter functions in the central nervous system and peripheral hypertensive effects. Most vasopressin effects have been reported to be mediated through one of two receptors: the V1 and the V2 receptor (128). The osmoregulatory renal effects are exerted mainly via the V2 receptor, a 40 kD membrane-spanning protein located in the collecting ducts (129). Maximal antidiuresis is accomplished if 2.5% or more of the renal V2 receptor sites are occupied (130). On a cellular level, the activation of V2 receptors leads to the synthesis of cyclic adenosine monophosphate (cAMP), which, in turn, results in the translocation of intracellular aquaporin type 2 to the apical cell membrane (131, 132). Aquaporin type 2 belongs to a group of water channel-forming proteins and is the molecule directly responsible for the vasopressin

During the first hours of sleep delta sleep (stage 3 and 4) dominates and

REM periods are short, but REM periods become longer and non-REM periods become more superficial as the night progresses(253, 254). The sleeper is most difficult to arouse during the first hours of sleep. Short moments of arousal into the waking state are usually interspersed throughout the night, most of them too short to be remembered in the morning. Furthermore, normal sleep is characterised by short, recurring bouts of accelerated pulse, EMG- and EEG-activation, and bodily movements, even though the sleeper does not become fully awake. Paediatric normal values of common neurophysiological sleep parameters, adapted from Coble (255, 256 , 257) are provided in Table 2. As can be seen in the table, there is a general tendency for the deep stage 4 non-REM sleep, and total sleep time, to decrease, as the child