5-hydroxytryptamine and sexual behaviour in rhesus monkeys
- Authors: Gradwell, Peter Bertram
- Date: 1976
- Subjects: Rhesus monkey -- Behavior Sexual behavior in animals
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3210 , http://hdl.handle.net/10962/d1012086
- Description: Selective inhibition of 5-hydroxytryptamine by parachlorophenylalanine (PCPA) is able to restore sexual receptivity in female rhesus monkeys made unreceptive by bilateral adrenalectomy. PCPA in the doses used reduces the levels of 5-hydroxyindoleacetic acid (5HIAA) in the cerebrospinal fluid to 40 per cent of the normal oestradioltreated condition. Both the increased sexual receptivity and the lowered 5HIAA levels "in the CSF are in turn reversed by 5-hydroxytryptophal (5HTP), the irrmediate precursor of 5HT and the substance whose synthesis is inhibited by PCPA. 5HTP on its own reduces sexual receptivity and increases 5HIAA levels in the CSF of ovariectomised, oestradiol-treated (but otherwise intact) female rhesus monkeys. A substance other than an adrenal androgen has therefore been shown to restore sexual receptivity in adrenalectomised female monkeys . Testosterone propionate and oestradiol benzoate both lower the turnover rates of 5HT in the brains of ovariectomised female monkeys, as measured by the 2 hour probenecid test. Taken together, these findings suggest that adrenal androgens could act on specific sites in the female monkey brain via 5HT-containing neural systems, to control (or at least influence) sexual receptivity. All the results of administering oestradiol to ovariectomised monkeys in these experiments are consistent with the established roles of this hormone in female sexual attractiveness and in the gonadotrophin- controlling systems of the hypothalamo-hypophyseal axis. In contrast to these findings on 5HT and sexual receptivity in female monkeys, no clear role for 5HT- containing neural systems could be demonstrated in the grooming, aggressive or social behaviours of female monkeys. No clear role for 5HT could be demonstrated in the refractory period following ejaculation in male monkeys , or when testosterone replacement is given to castrated male monkeys.
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- Date Issued: 1976
An investigation into the sensory mechanisms underlying the two point threshold, with particular reference to the practice effect
- Authors: Gradwell, Peter Bertram
- Date: 1971
- Subjects: Sensorimotor integration , Perceptual-motor learning
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3209 , http://hdl.handle.net/10962/d1012085 , Sensorimotor integration , Perceptual-motor learning
- Description: The two point threshold was studied extensively by the psychophysical experimenters of the last century. More recent formulations in signal detection theory have suggested that the statements of these workers about absolute thresholds should be viewed with caution. This study investigates the two point threshold in the light of these formulations, and has two main aims :- (1) To state and deal with the problem of relating a limitation in perceptual ability, such as that which is represented by the two point threshold, to the receptor organisation of the body. (2) To demonstrate a practice effect on the two point threshold, and to consider this in the light of (1) above. To fulfil these two aims, a model of the neural mechanisms underlying the discrimination of two points applied to the skin is proposed, and this is able to accommodate what is known of the two point threshold. Although the model is simple it explicitly accounts for size transfer and the practice effect, and provides some clues as to the type of neural mechanism capable of producing them. The practice effect is demonstrated experimentally, and the results are then referred to the model proposed. The physiology of an organism sets the limits for its behaviour. 'The first aim is thus an important one, in that it considers a specific case of this general problem. And secondly, the practice effect on the two point threshold is typical of a number of fairly simple "learning" phenomena, which are part of the psychologists' study of learning.
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- Date Issued: 1971