Hippocampal volume in postmenopausal cynomolgus macaques with behavioral depression

Area of Science:

• Neuroscience
• Primate Research

Background:

• Magnetic resonance imaging (MRI) studies indicate hippocampal (HC) volume reductions in depression.
• Ovarian steroid influence on the hippocampus is known, but regional volume changes and menstrual cycle phase effects are understudied.
• Previous in vitro work showed reduced anterior HC volume in behaviorally depressed, ovarian-intact female monkeys.

Purpose of the Study:

• To confirm in vivo findings of reduced hippocampal volume in behaviorally depressed female monkeys.
• To investigate the impact of ovarian steroid absence on the relationship between depression and HC volume.

Main Methods:

• High-resolution structural MRI was used to measure whole, anterior, and posterior HC volumes in surgically postmenopausal cynomolgus macaques.
• The sample included six behaviorally depressed and six nondepressed antidepressant-naive females.
• HC volumes were manually segmented and normalized to whole brain volumes.

Main Results:

• In vivo HC volume was associated with depression.
• Depressed surgically postmenopausal monkeys exhibited significantly smaller whole, anterior, and posterior volumes in both left and right hippocampi compared to nondepressed controls.
• These findings contrast with previous observations in ovarian-intact monkeys.

Conclusions:

• Smaller hippocampal volumes are confirmed in behaviorally depressed female monkeys.
• Ovarian steroids may play a protective role in the hippocampus concerning depression.
• Further research is warranted on how ovarian function modulates the depression-hippocampus relationship.