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Galanin immunoreactivity within the primate basal forebrain: evolutionary change between monkeys and apes
W C Benzing1, J H Kordower, E J Mufson
1Department of Neurological Sciences, Rush Presbyterian St. Luke's Medical Center, Chicago, Illinois 60612.
The Journal of Comparative Neurology
|October 1, 1993
Summary
Galanin expression in the basal forebrain differs between monkeys and apes/humans. Apes share the human pattern, indicating an evolutionary shift occurred before the ape lineage diverged from monkeys.
Area of Science:
- Neuroscience
- Evolutionary Biology
- Primatology
Background:
- Galanin immunoreactivity (GAL-ir) shows distinct patterns in the primate basal forebrain.
- Monkeys primarily exhibit GAL-ir within magnocellular basal forebrain neurons, while humans show an extrinsic galaninergic fiber innervation.
Purpose of the Study:
- To investigate the phylogenetic emergence of the human-like galanin expression pattern in the primate basal forebrain.
- To determine at which evolutionary juncture the shift from monkey-like to human-like GAL-ir expression occurred.
Main Methods:
- Comparative analysis of galanin immunoreactivity (GAL-ir) staining patterns.
- Examination of the basal forebrain in lesser apes (gibbons) and great apes (chimpanzees, gorillas).
- Comparison with previously established patterns in monkeys and humans.
Main Results:
- Apes (gibbons, chimpanzees, gorillas) exhibit a basal forebrain GAL-ir pattern similar to humans.
- GAL-ir was not found within magnocellular basal forebrain neurons of apes, contrasting with monkeys.
- A dense network of GAL-ir fibers innervated magnocellular neurons in apes, mirroring the human pattern. Scattered GAL-ir parvicellular neurons were also observed.
Conclusions:
- The evolutionary transition in basal forebrain galanin expression occurred at the divergence point between monkeys and apes.
- This suggests a significant evolutionary change in neural circuitry predating the emergence of great apes and humans.