You probably don’t need science to tell you that when you’re stressed out you’re not likely to be in the mood. But can stress cause physical damage to your reproductive cells? A study published this month in the Journal of Sexual Medicine suggests that it just might.
Rats aren’t all that different from people. They like tasty food, the occasional cuddle with a teddy bear and of course, they like sex. But also like humans, when they’re under a lot of stress, they don’t really want to have sex, even when the opportunity arises.
This has already been documented in many studies, as has the fact that the number of certain cells in the testes (Leydig cells) is smaller in stressed-out male rats. But why are there fewer Leydig cells? What actually happens to a male rat’s sperm when he’s under stress?
The scientists subjected male rats to chronic, unpredictable mild stress. These rats were exposed to different sources of stress at random intervals, at least to the rats, for 35 days. What kind of things stress out a rat? Well, the sort of things that would probably stress you out, too. First, the rats in the stress group were kept in individual cages for the whole 35 days. Just like people, rats are social animals. Being kept alone for a long time is a source of stress for them. Other sources of stress were: food or water deprivation for 24 hours, a 1 minute tail clamp, a small electric shock to the foot (30 times, for 10 seconds each, with a minute in between), 5 minutes in cold water, 24 hours in a cage with wet bedding, and a reversed light cycle. Another group of rats, used as controls, were kept together in a cage, in a different room, without any disturbances other than changing their food/water and bedding.
First, the researchers made sure that the stress in fact lowered libido. Male rats in the stress group didn’t show any special attention to the smell of female rats in heat, in contrast to the control rats who were very curious indeed about where those sexy lady rats were at.
Next, the researchers continued on to the fun part: slicing and dicing. They examined the male’s testicular cells for signs of damage. As expected, the control rats had healthy, normal-looking testicular cells and sperm. On the other hand, the stressed rats were all messed up. The cells where sperm are formed (seminiferous tubules) were of irregular size and shape, sperm in the tubules—which can normally be easily separated into groups based on how mature they are—couldn’t be told apart, and there were fewer sperm overall. Leydig cells, which pump out testosterone in the testes, were also affected by stress. As expected based on previous studies, there were fewer of them, but they were also much smaller than in the non-stressed rats. This could explain why the stressed rats weren’t too interested in meeting lady rats for sex: they were producing far less testosterone.
Upon closer inspection of the sperm, the researchers could see that they were not happy sperm. The sperm had large bubbles (called vacuoles) in them and their mitochondria (which produce the energy needed for sperm to swim) were swollen. Both are signs of cell damage and early indicators of programmed cell death.
This study didn’t show a direct effect of stress on the ability to sire offspring, but previous work has made the connection. A study in 2000 found that when male rats were subjected to immobilization-induced stress (ie: they weren’t allowed to move for a long time), even when they did mate with a female, she was twice as likely to miscarry.
So there you have it. Yet another reason to be stressed out about all the stress in your life. Happy Monday!
Hou G, Xiong W, Wang M, Chen X, & Yuan TF (2014). Chronic stress influences sexual motivation and causes damage to testicular cells in male rats. The journal of sexual medicine, 11 (3), 653-63 PMID: 24373463
Almeida SA, Kempinas WG, & Lamano Carvalho TL (2000). Sexual behavior and fertility of male rats submitted to prolonged immobilization-induced stress. Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas / Sociedade Brasileira de Biofisica … [et al.], 33 (9), 1105-9 PMID: 10973146