While testosterone is often thought of as the source of male libido, the nervous system plays a crucial role as well. In fact, three nervous system messengers (that is, neurotransmitters)—dopamine, glutamate, and serotonin—impact male sexual health.
Players in Male Libido
What is Dopamine?
Dopamine plays an important role in emotion, motor control, focus, working memory, and feelings of reward and pleasure. Imbalanced dopamine can play a role in cravings, poor mood, loss of muscle control, and focus issues.
What is Serotonin?
Commonly considered an inhibitory, serotonin is best known for its roles in mood, the sleep-wake cycle, and impulse control. As such, low levels have been linked to anger, sleep issues, mood issues, cravings, aches and discomfort, and low libido.
What is Glutamate?
Glutamate is the main excitatory neurotransmitter in the brain. Because of its stimulating effect, too much can lead to problems. For example, high levels can damage nerve cells. High or imbalanced levels can also lead to anxiousness, stress, and poor mood. On the other hand, low levels have been linked to fatigue and poor brain function.
What is Testosterone?
Testosterone is a sex hormone primarily produced in the gonads. A small amount is also made in the adrenal glands. It is well known for its role in contributing to physical traits such as muscle strength and mass, facial and body hair, and sperm production. However, it is also involved in libido, vitality, bone density, fat distribution, and production of red blood cells to name a few of its other effects. Imbalances in this hormone can lead to decreased sexual desire, changes in sleep, reduced muscle mass and decreased self-esteem.1
Nerves and Male Libido
The male libido is complex. It results from a combination of the physical and emotional aspects of the body. To integrate these areas, the body uses hormones and neurotransmitters. Steroid hormones, such as testosterone, prime the body to respond to sexual cues. They do so, in part, by affecting neurotransmitter function.2 However, the nervous system signals are the fast-acting, “in the moment” actors.2
Dopamine and Testosterone: A Two-Way Path
The relationship between dopamine and testosterone are interrelated. Dopamine can influence testosterone and the converse is true as well. In males, a key area of the brain for sexual function is the medial preoptic area (MPOA).
One study found that microinjecting dopamine agonists (which mimic dopamine function) in the MPOA of rats led to an increase in sexual activity.3 Another study found castrated male rats showed no interest in sex. And, dopamine was not released in the MPOA. After testosterone injections, the castrated rats engaged in sexual intercourse. There was also an increase in dopamine release in the MPOA.4
These studies reveal how critical dopamine is for libido. They also highlight testosterone’s role in dopamine release. While the MPOA is important for performance, there are two other brain regions critical for the sexual drive that involves dopamine.
One part of the brain is known for its role in pleasure and reward (VTA). Dopamine is the primary neurotransmitter in this system. Here, the actions of dopamine elicit the desire to engage in sexual activity.2 What dopamine’s activity does for sexual desire, it does in another region of the rat brain to motivate physical activity.2,5
But as stated above, the dopamine-testosterone relationship is not one-sided.
The Hypothalamic-Pituitary-Gonadal Axis
Testosterone production is controlled via a feedback loop called the hypothalamic-pituitary-gonadal (HPG) axis. The hypothalamus secretes a gonadotropin-releasing hormone (GnRH). Signals to the pituitary gland by GnRH cause the release of luteinizing hormone (LH). In turn, LH signals the gonads to produce testosterone.
One study observed dopamine impacts the HPG axis and as a result, testosterone production. Researchers found administering a dopamine agonist in rat brains increased amounts of GnRH mRNA by 67%.6 Thus, healthy dopamine function is necessary to make testosterone.
Glutamate Impacts Dopamine
As it turns out, healthy dopamine levels require glutamate for optimal sexual function. Stimulation of the medial amygdala by glutamate increases dopamine in the MPOA.2 Glutamate is also thought to impact the two systems involved in emotional and physical sexual activity.2 In fact, microinjection of glutamate into the MPOA of rat brains increased dopamine levels and led to erection.2
Dopamine and Serotonin at Odds in Male Libido?
Dopamine contributes to the desire for sexual activity, erection and ejaculation. Serotonin, on the other hand, is generally thought to inhibit libido. However, serotonin’s role is much more complex. In some cases, it enhances sexual activity.
Serotonin is important for erection and controlling ejaculation.2,5 (It turns out too much dopamine has been connected to premature ejaculation.)2 However, preventing serotonin reuptake has been shown to prevent erections and decrease sexual interest.2,5 It appears to be related to the receptor type and to serotonin levels.
It may be that too much serotonin may inhibit sexual activity, but too little could mean premature ejaculation. So, the goal is to achieve optimal levels. In addition, serotonin and dopamine levels need to be balanced.
Summary of Neurotransmitter Effects on Male Libido
The table shows the general roles of nervous system biomarkers involved in male libido. However, it is vital to remember two things. One, the neurotransmitters must be present in adequate levels along with adequate levels of testosterone. And two, they must be in balance with each other for optimal performance.
For men suffering from low libido or those wanting to enhance performance, the balance between neurotransmitters and testosterone is very important.
Neurotransmitter and hormone levels can be assessed easily with NeuroLab’s easy, at-home collection tests available through Sanesco. Sign up or log in to order the HPA-G Complete profile. If you are a patient, find a healthcare provider near you.
Maintain healthy sexual performance using Targeted Nutritional TherapyTM formulas designed to support healthy levels of dopamine, glutamate, and serotonin.*
Originally published March 10, 2016. Updated June 18, 2019.
- Sexual health. Testosterone therapy: Potential benefits and risks as you age. Available at: http://www.mayoclinic.org/healthy-lifestyle/sexual-health/in-depth/testosterone-therapy/art-20045728. Accessed March 4, 2016.
- Hull EM, et al. Physiology and Behavior. 2004 Nov.;83(2):291-307.
- Dominguez JM and Hull EM. Physiol Behav. 2005;86: 356-368
- Putnam SK, et al. Hormones and Behavior. 2001;39(3):216–224.
- Nagaraj AKM, et al. Online Journal of Health and Allied Sciences. 2009 Jan.;8(1).
- Li S and Pelletier G. Endocrinology. 1992;131(1):395–399.
*This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.