Stimulation of Amygdaloid Nuclei and Periamygdaloid Cortex With Special Reference to Its Effects on Uterine Movements and Ovulation

Abstract

Summary A series of experiments was performed in an attempt to establish the anatomical localization of the effects upon uterine movements and ovulation due to the stimulation of the amygdaloid complex. A remarkable change in the uterine movements was recognized through electrical or chemical stimulation of delimitd parts of the amygdaloid nuclei in dogs, cats and rabbits. In pxtpartum and in non‐pregnant matured animals, as well as in the latter half of pregnancy, an increase of tonus in uterine musculature and auginentation in frequency and amplitude of uterine motility can be evoked through unilateral stimulation of the medial principal amygdaloid nucleus (T of Völsch). These effects vary more or less according to the animal species and rather greatly by the stadium of sexual cycle at the time of experimentation. Stimulation of the lateral principal nucleus (M of VöZsch), the intermediate principal nucleus (T' of Vösch), the so‐called cortical amygdaloid nucleus (B of Vösch), the medial amygdaloid nucleus (D of Vösch) and the central amygdaloid nucleus (E of Vösch) seems to be altogether ineffective. Stimulation of the periamygdaloid cortex gives an equally hardly effect upon the uterine motility. The impulse from the amygdala passes very likely through fibers corresponding to MV or MD fiber described by Fukuchi in Ungulata or through so‐called medial forebrain bundle and is led to the viscero effective centre of the hypothalamus. The electrical stimulation of nuclei T and T' of the amygdala is capable of producing ovulation or hemorrhagic follicle in the ovary of the matured estrous rabbit. The impulse seems to go from the amygdala directly to the ventro medial nucleus of the hypothalamus leading further to the anterior pituitary lobe. The further effect to the ovary may be governed by the gonado tropic hormone released from the anterior pituitary lobe. In this latter case the estrous phase of the animals may also play an important rôle. (This work was aided in part by a grant from the Science Research Foundation of the Educational Department.

The Origin of the Efferent Projections From the Amygdaloid Complex to the Preoptic Area of the Rat, Studied by the Retrograde Transport of Horseradish Peroxidase (Hrp)

“…Our present results clarified that the origins of the amygdalofugal fibers to the preoptic area are phylogenetically older portions of the amygdaloid complex. We also partially proved that the corticomedial group of the amygdaloid complex was concerned with ovulation (13,14), but the cortical and basal nuclei which Koikegami (13,14) stimulated in order to observe ovulation in 1954 showed no positive reaction in the present study.…”

“…The significant role of the amygdaloid complex in the release of gonadotropin has been studied by several investigators (4,7,12,16,23), and it is generally accepted that the impulses from the amygdaloid complex which trigger ovulation (3,13,14) may be transmitted to the preoptic area (10, 24) passing through the stria terminalis (25), and accelerating the release of LH-RH (11) which is mainly produced in the neurons in the preoptic area (2).…”

Lateral Asymmetry in Activation of Hypothalamic Neurons with Unilateral Amygdaloid Seizures

“…The amygdala can be divided into two cytoarchitectonically distinct functional divisions, corticomedial and basolateral, which exert opposing modulatory influences on the hypothalamus by largely separate outflow tracts, the stria terminalis and the ventral amygdalofugal pathway (24). For example, stimulation of the corticomedial amygdala can induce ovulation and uterine contraction (25,26). Transection of the stria blocks this ovulatory response, whereas lesion of the ventral amygdalofugal pathway does not (26).…”

The Effects of Sex Steroids and Ovulation Inducing Stimuli on the Hypothalamus and the Limbic System

“…and a half on the hypothalamus as well as on the limbic system. (Koikegami et al, 1954;Kawakami et al, 1967). Many studies concerned with gonadal function and the mechanism of ovulation have been reported in relation to these two areas, and consequently the electrophysiological activity of each area, independently, has been clarified to some extent.…”