Behavioural effects of oestradiol in the female rat

Using behavioural and physiological measures, this thesis investigates behavioural effects of oestradiol, and of two of its synthetic analogues, mestranol and ethynyl oestradiol, in the female rat. Two types of behaviour receive particular attention, feeding and sexual behaviour. The first chapter describes some physiological and behavioural changes in the female rat over the oestrous cycle. Changes in meal size are seen during oestrus, or in ovariectomlzed rats treated with oestradiol. The effect of oestradiol on the gastric emptying of saline, glucose and fat loads was investigated (Chapter 2) to determine whether changes in stomach emptying were responsible for altered meal size. Only the emptying of fats from the stomachs of oestradiol treated rats was significantly reduced. The role of oestradiol in motivational processes associated with sexual behaviour was also examined (Chapter 3). It was found that the performance of females, running to sexually active or castrate males in a straight runway, depended on their oestrous state, and the gonadal condition of the males. These were independent and additive effects. The characteristics of the potent male that were rewarding to a female were then investigated by varying the odour and sexual activity of male rats (Chapter 4). The results suggest that both the odour and sexual activity of a potent male are rewarding to a female rat. Ethynyl oestradiol and mestranol are synthetic oestrogens nonnally used in oral contraceptives. The experiments presented in Chapter 5 show that in female rats both of these steroids reduced food intake reliably, and more than oestradiol. Ethynyl oestradiol, but not mestranol, stimulated sexual behaviour. Furthermore, there was no interaction between oestrogen and progestogen components of oral contraceptives which influenced, in any way, the behaviours observed in this study. The final chapter reviews the effects of oral contraceptives on mental, somatic and behavioural changes in women

Social especially agonistic behaviour in the pigeon

This study describes the social behaviour of the pigeon, with particular reference to agonistic behaviour. The ethogram, presented In Chapter 2, Includes a description of the aggressive, courtship and maintenance behaviour patterns of pigeons. A selection of sonograms of pigeon vocalisations, which shows the diversity of the calls, and their association with the accompanying behaviour, is presented. The function and causation of some of the behaviour patterns are discussed. In an attempt to investigate the mechanisms involved In the regulation of aggression between conspecific neighbours, the agonistic behaviour shown by a dominant male pigeon, when allowed to Interact with a subordinate male, was recorded over 10 days (Experiment 1). It was found that aggressive behaviour showed a large decrement over the first two days. Threatening behaviour became more evident thereafter. The causal and functional significance of these and other agonistic behaviours are discussed In this context. It was shown that diurnal rhythms did not affect agonistic behaviour. The effects of total social Isolation on agonistic behaviour was investigated in three male pigeons (Experiment 2). The results obtained do not suggest a build-up of an "aggressive drive", during the periods In isolation, which is expressed through the performance of aggressive behaviour after isolation. The possible effects of Isolation on other agonistic behaviours are discussed

Meal Patterning of Rats with Changes in Day Length and Food Availability

Feeding activity in rats is mainly nocturnal, with about 70-90% of the total daily intake eaten in the dark phase. During this phase, feeding has a typical biomodal pattern, i.e. a high level of feeding activity early and late in the night. The aim of the present study was to investigate the effects of temporary food restriction at dawn and dusk, and advanced light onset on the bimodal feeding pattern of male rats. It was found that suppression of food intake by restricting access to food or altering light onset act in radically different ways on the circadian meal patterning. It is argued that food restriction led to a general metabolic deficit, which was compensated by an increase in intake, especially after deprivation. Advancing light onset shifted the "dawn peak" of food intake to precede light onset. The results suggest that under these experimental conditions advancing light onset but not temporary food restriction can "reset" the circadian pacemaker.

Effect of Skeleton Photoperiod and Food Availability on the Circadian Pattern of Feeding and Drinking in Rats

Feeding and drinking behavior were measured in rats maintained under a 12:12 light-dark (LD) cycle or skeleton photoperiod (SPP). Feeding and drinking were closely associated during the normal LD cycle but under SPP conditions an increased feeding activity during the subjective day was not accompanied by an equivalent increment of water intake. This indicates a stronger coupling of drinking to the subjective night. A restriction of food availability to the subjective light phase did not cause an accompanying complete shift in drinking behavior. These results suggest that drinking is largely dependent on the influence of a circadian oscillator and this association is not disrupted by changes in feeding schedule. A change in food access to the subjective light phase caused partial but not permanent desynchronization between feeding and drinking behavior. Synchrony was reestablished within one day once food was available ad lib. Complete return to the original feeding and drinking patterning took 3 days. It is suggested that separate slave oscillators controlling feeding and drinking are governed by a hypothesized "master" circadian oscillator which remains definitely entrained to the original rhythm by the light pulses of the SPP condition.