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Mystical “Catnip” May 3, 2011

Posted by mhostetler099 in Behavior, Biology, Chemistry, Health, Physiology.
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So what is it about “catnip” that makes cats crazy, mosquitoes fly away and at the same time has seemingly no effect on human beings?  In actuality, the better question is what are the distinguishing factors allow different organisms to interpret “catnip’s” chemical signal differently or not at all.

The 6th Sense (the vomeronasal organ in cats)

It is well documented that all mammals posses 5 senses (sight, taste, touch, smell, hearing); BUT could mammals have a 6th sense?! Some scientists would say YES and pinpoint this sense to be related to the mysterious vomeronasal organ located above the roof of the mouth.  This sensory organ is attributed to sensing chemical signals from other organisms and the environment known as pheromones.  The vomeronasal organ is present in most mammals and is considered a chemoreceptor organ which exists as a separate entity than the nasal cavity.  Chemoreceptors detect chemical signals from the organism’s environment and transduce a physiological response accordingly. Studies indicate that nepetalactone (the chemical produced by “catnip”) is responsible for eliciting a psychosexual response in cats by mimicking a sex pheromone and interacting with the feline vomeronasal organ.  Although human beings and felines are both mammals, they react to the chemical in “catnip” much differently than one another.  “Catnip” elicits no response in human beings and a rather strong response in felines.  The distinction between these responses can most likely be attributed to a physiological difference in the feline and human sensory system.

The Vomeronasal Organ in Humans

The function of the vomeronasal organ in human beings is actually quite controversial.  Studies on human embryos have indicated that the vomeronasal organ does correspond to the vomeronasal organ in cats and other mammals.  Although the vomeronasal organ is common in both feline and human species, the organ in humans was thought by scientist to be vestigial (or no longer functioning).  The vestigality of the vomeronasal organ in human beings may explain why humans do not react to chemicals in “catnip” however this is an unlikely explanation because studies have shown human beings can react to pheromones.  Another explanation to the differing reactions could potentially be attributed to the physiological differences in the organs themselves (show left). 

 So Why are Mosquitoes Repelled?

So why are mosquitoes seemingly repelled by some essential oils extracted from different plants and herbs (including “catnip”)?  This question is a little more difficult to answer directly because little is known about insect sensory system.  Studies have shown that mosquitoes are more attracted to people with high concentrations of steroids and cholesterol on the surface of the skin.  Mosquitoes are attracted and repelled by certain pheromones.  More than likely, the chemical nepetalactone in “catnip” is able to mimic a pheromone that triggers a chemical signal causing the insect to become repelled (acting as an insecticide).

It is truly amazing that the same chemical can signal different responses in different organisms.  The responses to chemical signals in the organism’s environment are evolutionarily beneficial; whether it be to attract a mate or flee from impending danger.  According to a news report conducted by NPR the CDC is working on natural repellant consisting of extract from cedar tree.  This substance is completely environmentally friendly and actually acts as an insecticide.  It is able to kill the mosquitoes by blocking receptors on their nerve cells (absent in human beings).  Although the chemical found in “catnip” is not known to be an insecticide, the similarity between natural extracts (from “catnip” and cedar tree) may certainly explain insects natural repulsion from them.

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