If you go to the archives, you will find that my very first column
dealt with nitric oxide, NO, and peripherally, with Viagra. Last
week, thanks to the detection of some red blood cells in my
urine, I had the dubious pleasure of undergoing a couple of
medical procedures previously unknown to me. One was a
cystoscopy to check out the bladder and the prostate. This
procedure requires the urologist to insert and thread an
observational device into and through that part of the male
anatomy hardly ever mentioned by its proper name until the Bill
& Monica episode. With my legs up in the stirrups and being
told to breathe in and out deeply, I found the cystoscopy to be as
close as I care to get to the feeling a woman must have during
childbirth.
Fortunately, nothing serious was found and you”ll have to put up
with these columns for at least a little while longer. That
evening, somewhat drained by the ordeal, I decided to attack my
stack of unread journals. In the August 2000 issue of Scientific
American, what should I see but an article titled “Male Sexual
Circuitry” by Irwin Goldstein and the Working Group for the
Study of Central Mechanisms in Erectile Dysfunction. This
Working Group consists of about ten workers from various
universities. The next day, I read in an issue of Forbes magazine
that two drugs meant to compete with Viagra had been sidelined
because of possible side effects. All in all, I felt that this week
I had no choice but to write about the penis.
What really caught my eye was mention of Leonardo da Vinci in
the first sentence of the Scientific American article. Last year, I
noted in one of these columns that my wife and I had been to
Milan in Italy and that we had waited many hours in line to see
da Vinci”s recently renovated “Last Supper”. Some 500 years
ago, Leonardo was not only painting, but was also among many
scientists and others who have had a keen interest in what lies
behind the erectile functioning of the penis. In fact, Leonardo
was apparently the first to realize that the penis fills up with
blood during an erection. He came to this conclusion through
his dissections of the penises of men who had been hung for
various and sundry deeds! And this is the man who also painted
the Mona Lisa!
The article quotes da Vinci as saying, “The penis does not obey
the order of its master, who tries to erect and shrink it at his
will…. The penis must be said to have its own mind, by any
stretch of the imagination.” It certainly seems that Leonardo was
right on target in his first statement, judging from the popularity
of the drug sildenafil (Viagra). However, his belief that the penis
has a mind of its own is not true.
The brain and spinal cord, which comprise the central nervous
system, really control the processes of erection and
detumescence, the return of the penis to its normal limp or
flaccid state. Now you might think that nothing much is going
on normally, when the penis is just hanging there minding its
own business. On the contrary, it has to be continuously told to
stay in that condition. During the normal course of the day, the
so-called sympathetic nervous system is busy sending signals.
These signals tell the blood vessels in the penis to remain
relatively constricted so as to prevent the influx of blood that
gives rise to an erection. Thus it takes a form of positive control
to prevent the penis from being permanently erect.
On arousal, appropriate signals arrive at the penis, where certain
nerves release nitric oxide and other chemicals that in turn signal
the muscles in the penis to relax. This allows blood to flow into
and fill spongy chambers within the penis. The expansion of
these chambers compresses the veins through which the blood
normally returns. This prevents or slows down the blood flow
out of the penis and the erection is maintained. During this time
the penis itself is not totally passive. It is sending signals back
to the spinal cord and brain, keeping them abreast of what”s going
on. When ejaculation occurs or the male becomes disinterested,
the sympathetic nerve system quickly starts sending signals that
cuts the blood flow to the penis and it”s back to the flaccid state.
Surprisingly, the spinal cord itself can generate erections without
the brain being involved. This finding came about in World War
II, when veterans with spinal cord injuries were thought to be
impotent and sterile. In a landmark study in 1949, a Dr. Talbot
found that out of 200 paraplegics, two thirds were able to have
erections and in some cases engage in intercourse with orgasm.
This and older studies in animals led to the discovery of a center
just above the tail end of the spine that can generate erections if
that center and the signaling system to the penis remain intact.
Signals from the penis to this region lead to stimulation of certain
neurons and it”s these neurons that send the erection signals to
the appropriate nerves.
Studies with rats and with men have revealed another surprising
result. When the brain is disconnected from the spinal erectile
center, the erections may actually be much more frequent and
require less in the way of arousal than before the disconnect. In
the rat, the area of the brain in charge of the normal signals that
inhibit the formation of erections was identified. When that part
of the brain was destroyed the inhibition was removed and more
frequent and intense erections resulted.
All in all, you can see from this very brief synopsis of the article
that the male erection is no simple matter. (Perhaps not
surprisingly, the counterpart form of arousal in women seems to
follow along in a pretty similar manner as in men. However, the
studies on women have not been as thorough to date.) The
inhibitory signals to prevent erection can play an important role
in the lifestyle of men. Too much inhibition and you have sexual
dysfunction; too little and you have a man who may lead a sex
life that puts him or his partners at risk for various sexual
diseases, etc.
The article also discusses the role of various common
medications such as those that affect serotonin levels. Such
drugs are often taken to treat depression and various mental
problems. The resulting increased serotonin levels can enhance
the inhibitory mechanisms and, as a side effect, lead to sexual
dysfunction. At the same time, for other men suffering from
premature ejaculation, the same drug may be a blessing, allowing
them to delay orgasm. One man”s problem can be another”s
salvation! There is much more covered in this article but this
gives the overall flavor. If any ladies have read thus far, I hope
that you ladies appreciate that it”s a complex matter for your guy
to perform what looks to be a pretty straightforward act.
Of course, I know that most of you are really much more
interested in the sex life of fireflies, subject of an article in the
June 29 issue of Science. Those bursts of light from their
lanterns are signals passing back and forth between male and
female fireflies on the prowl looking for mates. Now, in what
appears to be a landmark study in firefly sexuality, Barry
Trimmer and his coworkers at Tufts University have linked the
firefly”s flashing lights to nitric oxide, NO. In my first column, I
discussed how NO plays a key role in our bodies and how one
aspect of Viagra”s effectiveness is related to the control of NO.
Through a series of clever experiments, Trimmer”s team showed
that NO is the mediator that turns the lantern on. They did this
by exposing the fireflies to high concentrations of NO. The
fireflies lit up and didn”t turn off. To confirm the finding, the
team wanted to make sure that NO wasn”t just affecting the
nerves that trigger flashing. So they operated on the fireflies,
separating the nerves from the lantern and then added NO. Sure
enough, the flashing commenced even though the lantern was
isolated. Why does the light turn off? Earlier researchers have
shown that light tends to inhibit NO. So the light itself turns off
the NO, and the lantern shuts off. Hence the repeated flashing in
the search for a bit of fun and frolic.
Well, that”s enough torrid talk on sex. Next week, I think I”ll
switch to another hot topic, global warming.
Allen F. Bortrum
