Pheromone-induced learning: a NEW model?

Science 14 December 2012: Vol. 338 no. 6113 pp. 1462-1465 (subscription required)

Pheromonal Induction of Spatial Learning in Mice

Abstract excerpt: “…pheromone-induced learning allows animals to relocate sites of particular social relevance and provides proof that pheromones such as darcin can be highly potent stimuli for social learning.

My comment to Science (Received: Thu, 13 Dec 2012 17:46:58 -0500/published more than a month later 1/15/13): In my model, the reliable and rapid learning induced by the sex pheromone darcin would best exemplify the top-down epigenetic effect of pheromones on intracellular signaling and stochastic gene expression that controls bottom-up nutrient-chemical dependent reproduction in species from microbes to man.

In mammals,for example, the epigenetic effects of the nutrient chemicals and pheromones converge on the same neuronal system. It is their epigenetic effects on the gondadotropin releasing hormone (GnRH) neuronal system that also links epigenetic cause and effect to juvenile hormone (JH) secretion in the honeybee model organism. This is a form of evolutionary back-tracking from vertebrates to invertebrates in the context of hormone-organized and hormone-activated behaviors (vertebrates: Diamond, Binstock and Kohl, 1996; invertebrates: Elekonich and Robinson,2000).

However, invertebrate models best exemplify the requirement for adaptive evolution to get from gene expression to behavior and back. What the honeybee queen eats determines her pheromone production and everything else about the behavioral interactions in the colony, including neuroanatomy of the worker bees’ brains.

I’m not sure what makes including the observed affects of darcin on behavior a “new model” for use to investigate the neural pathways and mechanisms involved in spatial learning associated either with food odors or with the species specific social odors called pheromones. Was there something wrong with the old model in which nutrient chemical-dependent pheromone-controlled reproduction enables adaptive evolution via ecological, social, neurogenic, and socio-cognitive niche construction and the molecular mechanisms common to species from microbes to man? Doesn’t this “new model” eloquently elucidate the fact that epigenetic changes occur across an evolutionary continuum, which includes both nutrition-dependent reproduction in unicellular organisms and sexual reproduction in mammals?

In my model, for example: “Olfaction and odor receptors provide a clear evolutionary trail that can be followed from unicellular organisms to insects to humans.” — Kohl, J.V. (2012) Human pheromones and food odors: epigenetic influences on the socioaffective nature of evolved behaviors. Socioaffective Neuroscience & Psychology, 2: 17338.

Author: James Kohl

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