Effect of castration on medial preoptic/anterior hypothalamic neurone responses to stimulation of the fimbria in the rat.

1. Single unit extracellular recordings were made from medial preoptic/anterior hypothalamic neurones in response to electrical stimulation of the ipsilateral fimbria. The effects of castration on neuronal responses were investigated and the pathway of the fimbria input analysed using multiple stimulation and selective lesions.

Inputs to testosterone-sensitive stria terminalis neurones in the rat brain and the effects of castration.

1. The inputs to cortico-medial amygdala neurones which project directly to the area of the medial preoptic/anterior hypothalamic junction were studied electrophysiologically in urethane anaesthetized male rats. 2.

A quantitative analysis of the feeding behavior of suckling rabbits.

Three experiments are reported on the feeding behavior of suckling rabbits ("kittens"). In the 1st the latency with which the kittens attached to the nipple, and then left the nipple, was determined. Attachment was very rapid and wholly reliable: on the 80 tests the nipple was seized in every case in under 9 sec, and on 67 of these in less than 3 sec.

Effect of testosterone on neuronal refractory periods, sexual behaviour and luteinizing hormone: a comparison of time-courses.

Measurements of the refractory period of stria terminalis neurones that are sensitive to testosterone propionate, of sexual behaviour and of plasma levels of LH were taken in castrated rats at various times after initiation of treatment with testosterone propionate. Levels of LH dropped within 24 h, before there was any change in neuronal refractory periods. The period of latency to mounting, however, was reduced to its shortest only after 7-8 days and ejaculations first occurred at the same time; these sexual responses correlated in time with reduction of the neuronal refractory period to its lowest level.

Effect of testosterone and the oestrous cycle on neuronal refractory periods and firing rates of stria terminalis neurones in the female rat.

Absolute refractory periods of a subpopulation of corticomedial amygdala (CMA) neurones which project to the medial preoptic/anterior hypothalamic junction (MPH) via the stria terminalis were recorded in the female rat. Previous experiments have shown that this sub-population of CMA neurones is testosterone-sensitive in the male rat. In the ovariectomised female testosterone propionate (TP, 200 microgram/day for 18-22 days) significantly reduced the mean absolute refractory period of these CMA neurones compared to oil treated controls (from 1.

Testosterone-sensitive neurones respond to oestradiol but not to dihydrotestosterone.

Testosterone is aromatized to oestradiol in the brain, and it has been suggested that its effects on the brain are produced by this metabolite. Oestradiol does indeed restore sexual behaviour in castrated rats, but is is much more effective if combined with a second metabolite, dihydrotestosterone. This may be because the two hormones have a synergistic effect on the brain; or because the central effect of oestradiol synergises with the peripheral effects of dihydrotestosterone (which include stimulation of penile development).

Differentiation of learning disabled children from normal children using four coordination tasks.

Fifty 8-year-old children, 25 classified as normal and 25 as learning disabled, participated in a study to determine whether they could be differentiated into their respective groups by using four tasks from the Devereux Test of Extremity Coordination: opposition, foot patting, finger wiggling, and heel-toe walking with the eyes closed. Each chilld received numerical scores based on the number of times he could perform a task in 10 seconds. A stepwise discriminant function analysis revealed that two tasks, opposition and foot patting, were significant discriminating variables.

Testosterone reduces refractory period of stria terminalis neurons in the rat brain.

The absolute refractory period of neurons projecting from the corticomedial amygdala to the medial preoptic-anterior hypothalamic junction in rats was significantly increased by castration (from 1.01 to 1.61 milliseconds) and decreased again by testosterone (from 1.