Egg activation at fertilization in mammals is initiated by prolonged Ca2+ oscillations that trigger the completion of meiosis and formation of pronuclei. A fall in mitogen-activated protein kinase (MAPK) activity is essential for pronuclear formation, but the precise timing and mechanism of decline are unknown. Here, we have measured the dynamics of MAPK pathway inactivation during fertilization of mouse eggs using novel chemiluminescent MAPK activity reporters. This reveals that the MAPK activity decrease begins during the Ca2+ oscillations, but MAPK does not completely inactivate until after pronuclear formation. The MAPKs present in eggs are Mos, MAP2K1 and MAP2K2 (MEK1 and MEK2, respectively) and MAPK3 and MAPK1 (ERK1 and ERK2, respectively). Notably, the MAPK activity decline at fertilization is not explained by upstream destruction of Mos, because a decrease in the signal from a Mos–luciferase reporter is not associated with egg activation. Furthermore, Mos overexpression does not affect the timing of MAPK inactivation or pronuclear formation. However, the late decrease in MAPK could be rapidly reversed by the protein phosphatase inhibitor, okadaic acid. These data suggest that the completion of meiosis in mouse zygotes is driven by an increased phosphatase activity and not by a decline in Mos levels or MEK activity.

Light and smell have both been shown to induce beneficial changes to human psychophysiology. Bright light therapy has been shown to have a positive impact on anxiety and depression and smell has also been shown to have positive effects on mood, stress, anxiety and depression. We developed a method for the delivery of integrated light and smell stimulation to try to optimise positive psychophysiological benefit. We tested its effectiveness on a physiological measure, EEG frontal alpha asymmetry (FA) and a psychological paradigm, the POMS test, both of which have been used as a measure of emotional state and mood. Light, pleasant smell, combined light+smell and a no stimulus control were delivered for 90s while the frontal alpha asymmetry (FA) was monitored. Smell and light+smell caused significant reductions in negative FA during stimulation. Exposure to a longer 15 min nonadaptive light+smell stimulus protocol reduced negative FA and decreased negative affect (POMS). The effects were greater in the negative FA group. Both the physiological (EEG) and psychometric (POMS) data indicate that integrated light and smell stimulation can reduce negative affect and reduce a marker for anxiety/ depression. This light+smell sensory stimulation protocol could offer a safe treatment for depression/anxiety.