The estrous cycle modulates rat caudate-putamen medium spiny neuron physiology

Area of Science:

• Neuroscience
• Neuroendocrinology
• Electrophysiology

Background:

• The brain's neuroendocrine environment is dynamic and sex-specific, influencing behavior.
• Cyclical changes in sex hormones affect sensorimotor and cognitive functions, mediated by the caudate-putamen.
• Medium spiny neurons (MSNs) in the caudate-putamen are estrogen-sensitive but their electrophysiological properties across the estrous cycle are unknown.

Purpose of the Study:

• To investigate how estrous cycle phase influences the electrophysiological properties of caudate-putamen medium spiny neurons (MSNs).
• To compare MSN properties across different cycle stages (diestrus, proestrus, estrus) and with male MSNs.

Main Methods:

• Whole-cell patch-clamp recordings were performed on MSNs from male, diestrus, proestrus, and estrus female rats.
• Assessed action potential properties, passive membrane characteristics, and miniature excitatory post-synaptic currents.

Main Results:

• Numerous electrophysiological properties of MSNs significantly differed based on the estrous cycle phase.
• Key differing properties included resting membrane potential, rheobase, action potential threshold, firing rate, and inward rectification.
• When not considering cycle phase, most MSN properties did not significantly differ from male MSNs, indicating cycle-dependent modulation.

Conclusions:

• Caudate-putamen MSNs in females are highly sensitive to the neuroendocrine fluctuations of the estrous cycle.
• These findings underscore the critical importance of considering the neuroendocrine state, particularly the estrous cycle, in neuron physiology research.
• Future studies should account for hormonal variations to better understand brain function and behavior.