Love and chemistry

29 Nov 2005

"We have demonstrated for the first time that circulating levels of NGF are elevated among subjects in love, suggesting an important role for this molecule in the social chemistry of human beings," says Enzo Emanuele of the University of Pavia in Italy.

Dr Emanueleand his researchers compared 58 men and women, aged 18 to 31, who had recently fallen in love with people in established relationships and those who were single.

"Potential participants required to be truly, deeply and madly in love," said the researchers. Only people whose relationships had begun within six months were studied. The "in love" had to be spending at least four hours a day thinking about their partner.

When the levels of blood chemicals were measured, it was found that both men and women who had recently fallen in love showed very high levels of NGF - 227 units compared with 123 units recorded in those in long-lasting relationships. The study also found that those who reported the most intense feelings had the highest NGF levels.

However, when researchers revisited people from the "in love" group who were still in the same relationship more than a year later, the levels of NGF had declined to the same levels as the established relationship and singles groups.

Report about to be published in the journal Psychoneuroendocrinology

Neuronal Activity Related to Reward Value and Motivation in Primate Frontal Cortex

Science, Vol 304, Issue 5668, 307-310 , 9 April 2004 doi:10.1126/science.1093223

In several areas of the macaque brain, neurons fire during delayed-response tasks at a rate determined by the value of the reward expected at the end of the trial. The activity of these neurons might be related to the value of the expected reward or to the degree of motivation induced by expectation of the reward. We describe results indicating that the nature of reward-dependent activity varies across areas. Neuronal activity in orbitofrontal cortex represents the value of the expected reward, whereas neuronal activity in premotor cortex reflects the degree of motivation.

Enhanced partner preference in a promiscuous species by manipulating the expression of a single gene

Nature 429, 754 - 757 (17 June 2004); doi:10.1038/nature02539


A single gene inserted into the brain can change promiscuous male rodents into faithful, monogamous partners.

Hyperdopaminergic Mutant Mice Have Higher "Wanting" But Not“Liking” for Sweet Rewards

Peciña, Cagniard, Berridge et el.

Mutant mice with 70% elevated levels of synaptic dopamine demonstrated greater incentive performance for a sweet reward, e.g. require fewer trials to learn, pause less often in the runway, resist distractions better, etc. But sucrose taste fails to elicit higher orofacial “liking” reactions from mutant mice in an affective taste reactivity test, e.g. facial expressions, paw licking. These results indicate that chronically elevated extracellular dopamine facilitates “wanting”but does not increase“liking” reactions to the hedonic impact of sweet tastes.