As unromantic as it sounds, love results from biological responses to various neuropeptides and neurotransmitters (1). As such, love is more likely defined as a motivation than an emotion: it triggers goal-oriented behaviors to achieve successful reproduction (2). Interestingly, love is first initiated by a stress response associated with higher cortisol levels related to a fight/flight response (3). This romantic period, which can be defined by the attraction phase (1) that lasts between 6 to 24 months, has similarities with bipolar and obsessive-compulsive disorders where there is an increase of the norepinephrine and dopamine systems (4) in parallel with a decrease in serotonin (5). It is followed by the state of being in love: this attachment phase (1) aimed at creating pair bonding is mainly influenced by oxytocin, vasopressin, and dopamine (6). These neurotransmitters help reduce stress and favor the reward circuitry (4). It was also shown that monogamous mammals have higher oxytocin receptor density than polygamous species (7). Interestingly, sexual activity and attachment are intermingled: testosterone and estrogen, two neurotransmitters increased by sexual activity, helps reinforce the reward circuitry of attachment by stimulating dopamine release, while the activation of the dopaminergic pathway contributes to the release of testosterone/estrogen (4).
It is the least to say that a complex network of neurotransmitters, and their receptors, is at the heart of what we describe as a long-term romantic relationship. To evaluate neurotransmitter fluctuations, target-specific antibodies such as the anti-serotonin/5-HT MM-1019 (8), can be used in your studies. Happy Valentine’s day.