Effect of estrogen on the responsivity of hypothalamic and mesencephalic neurons in the female cat

doi:10.1016/0006-8993(69)90166-8

Brain Research

Volume 15, Issue 2, October 1969, Pages 439-446

https://doi.org/10.1016/0006-8993(69)90166-8 Get rights and content

Summary

The responsivity of hypothalamic and mesencephalic neurons to somatic, visual, acoustic and vaginal stimulation was studied in ovariectomized (anestrous) and estrogen-treated ovariectomized conscious cats (estrous) immobilized with Flaxedil. Comparison between the results obtained in the two groups revealed that in the anterior and medial hypothalamus estrogen facilitated the appearance of excitatory responses to all the types of stimulus used, whereas it reduced the number of inhibitory responses to vaginal stimulation. Excitatory responses to all sensory modalities clearly predominated over inhibitory ones in the mesencephalic reticular formation of anestrous cats. By contrast, a marked increased in the proportion of inhibitory responses, particularly to vaginal stimulation, was observed in estrous subjects. Our results suggest that estrogen affects differentially the responsivity of hypothalamic and mesencephalic neurons to peripheral stimulation.

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Citation Excerpt :
This suggestion could be supported by other research with rodents that has documented the action of androgens, such as T, on the mPFC and BLA during tasks that involve attention to conditioned stimuli (Kritzer et al., 2007; Agis-Balboa et al., 2009), together with increases in the AP of the theta band in the mPFC during working memory performance on sexually-motivated tasks (Hernández-González et al., 2012). It is well-known that one of the effects of steroids like testosterone induce changes in electrical activity of neurons (Alcaraz et al., 1969; Wong and Moss, 1991; Robel and Baulieu, 1994; Poblano et al., 2004). One study that showed the possible regulatory role of testosterone (or its metabolites) on the theta band in rodents was Del Río-Portilla et al. (1997).
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Neuronal activity of the lateral septal nucleus (LSN) is related to motivational and hedonic behavior. Even though some changes in mood and anxiety during proestrus and pregnancy have been reported, the possible changes in the neuronal activity of the LSN through the phases of the estrous cycle are unknown. In the present study we explored the neuronal activity from the LSN using glass micropipettes (NaCl 1 M, and Evans blue 2.5%; 3–8 MΩ) in 30 urethane (1 g/kg) anesthetized Wistar rats. Analysis of data included a total of 88 single-unit extracellular recordings taken from the LSN during proestrus (n = 22), estrus (n = 23), diestrus (n = 22), and metestrus (n = 21). The highest values of firing rate were found in proestrus, and the lowest in metestrus, F(3, 84) = 3.78, p < 0.01. During estrous cycles, in the phase characterized by high plasma levels of estradiol and progesterone, i.e., proestrus–estrus, the neurons from the dorsal aspect of the LSN fired at significantly (p < 0.05) higher frequencies, shorter first-order intervals and a lower coefficient of variation than those in the phase characterized by lower levels of estradiol and progesterone (metestrus–diestrus). In another group of rats (n = 12), immobility in the forced-swim test was assessed. Consistently, a longer latency (p < 0.05) for the first period of immobility and a nonsignificant trend to a lowered total time in immobility were found in proestrus and estrus. It is concluded that the higher firing rate in neurons from the dorsal aspect of the LSN during proestrus–estrus, may be associated with an increased motivation to escape from a stressful situation.

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Effect of estrogen on the responsivity of hypothalamic and mesencephalic neurons in the female cat

Summary

Exp. Neurol.

Exp. Neurol.

Exp. Neurol.

Hypothalamic unit activity related to control of the pituitary gland

Electrophysiological alterations in adrenalectomy

Arch. Neurol. (Chic.)

A technique for recording and integrating unit activity

Bol. Inst. Estud. méd. biol. (Méx.)

The activation of sexual behaviour by hypothalamic implants of estrogen

J. Physiol. (Lond.)

Studies of brain metabolism and electrical activity in relation to adrenocortical physiology

Recent Progr. Hormone Res.