Everyone knows cats go crazy for catnip. It’s an effect that’s been noted in scientific literature as far back as the 18th Century, when scientists observed that cats seemed to be attracted to catnip when the plant was withered or bruised. Since then, research has managed to amass a little more detail on exactly why catnip affects cats in the way it does.

Firstly, a little background on what exactly catnip is. It’s a plant that’s a member of the same family as mint; in fact, one of catnip’s alternate names is ‘catmint’. When cats are exposed to the smell of catnip, their behaviour can take a turn for the strange. Their response to the scent has previously been categorised into four components:

Sniffing.

Licking, chewing and head shaking.

Chin and cheek rubbing.

Head-over rolling and body rubbing

Source: Todd: Inheritance of the Catnip Response in Domestic Cats (1962)



As well as these, stretching, leaping, sexual stimulation and euphoria have also been noted. This behaviour is a response to a specific chemical, nepetalactone, which occurs in the plant. Nepetalactone and its isomers make up 70-99% of the essential oil that can be obtained from the catnip plant – 4aα,7α,7aα-Nepetalactone is the specific isomer responsible for the catnip effect, but for ease we’ll just refer to it throughout as nepetalactone.

The exact mechanism through which the response is caused still isn’t precisely known, but scientists have a pretty good idea of the general steps involved. Firstly, nepetalactone will enter the cat’s nasal tissue, and there it will bind to certain receptors. These can then trigger particular sensory neurons to signal to other neurons, and eventually the brain; in particular, the ‘olfactory bulb’, a region at the front of the brain responsible for processing smells. This region then signals other regions of the brain, including the amygdala, responsible for emotional responses to stimuli, and the hypothalamus, responsible for behavioural responses to stimuli. This results in the observed response in cats – a response that is actually similar to their response to natural sex pheromones.

The effect of catnip lasts for around ten minutes, and afterwards there will be a refractory period of around an hour where the cat will remain unaffected. Interestingly, not all cats are affected by catnip; the response is genetic, and autosomal dominant, which means if one parent passes on the gene, then the offspring will inherit the response. Around 70-80% of cats are affected by catnip, with the remaining 20-30% exhibiting no reaction to it whatsoever. Additionally, very young cats are also unaffected by catnip, until they reach sexual maturity. The figures stated for the age up to which they are unaffected are variable, but generally 6-8 weeks old is the most frequently mentioned.

Nepetalactone doesn’t just affect domestic cats, either. It also has documented effects on lions, tigers and leopards, and additionally it can have effects on selected other animals. Notably, it can be used as a mosquito and fly repellent, and in humans it can act as a mild sedative and anti-spasmodic agent. It doesn’t affect humans in the same way as cats, as the human brain is physiologically different from that of a cat.

If you’re not a cat owner, or you’ve never seen the effect of catnip on cats, you can watch this clip from the BBC’s ‘Weird Nature’ series, which shows just how odd cats get in its vicinity.



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