The trigeminocardiac reflex (TCR) is a physiological response characterized by a reduction in heart rate and arterial blood pressure following stimulation of any branch of the fifth cranial nerve. This review presents a novel mechanism of TCR induction through proprioceptive activation of the trigeminal nerve via mandibular extension (ME). Accordingly, it is referred to as the “proprioceptive trigeminocardiac reflex” (pTCR). An overview of the existing literature on ME-evoked TCR in humans and animals is presented, with particular emphasis on evidence of cerebral microcirculatory alterations. The magnitude of cardiovascular responses appears to depend on the duration of ME, with repeated applications producing more pronounced and prolonged effects, particularly in hypertensive subjects. In rats, pTCR induction is accompanied by a marked increase in pial arteriolar diameter within the frontal and parietal cortices, apparently independent of neurovascular coupling. Anatomical studies propose a putative neural pathway underlying the pTCR, originating in the mesencephalic trigeminal nucleus and projecting to cardiovascular control centers within the brainstem. Experimental evidence indicates that the TCR may represent a centrally mediated neurogenic reflex resulting in decreased arterial pressure and cerebrovascular vasodilation. A deeper understanding of this reflex may pave the way for developing noninvasive interventions aimed at preventing or delaying the onset of hypertension and stroke, both of which are increasingly prevalent in Western populations.

The use of oral appliances is considered effective in improving sport performance. Jaw clenching or stretching, improved breathing or positioning of the jaw have been proposed to explain the improvement. In this study, we reported the effects of regularly practiced mandibular stretching at submaximal opening of the jaw in Crossfit athletes. Seventeen test subjects undergoing mandibular stretching (MS) showed significantly reduced (p0.001) performance time in a high-intensity workout measured before and after seven days of 10-minutes stretching practiced twice daily, while no improvement was observed in control subjects who did not perform the stretching. Additionally, blood lactate levels appeared to recover more quickly in MS subjects.Crossfit is a type of training regimen that pushes the limits of bodily recovery processes. Jaw stretching, eliciting the trigeminocardiac reflex (a reflex decrease in heart rate and blood pressure following trigeminal stimulation) and central oxygen-conserving mechanisms could help relieve post-training stress and improve training recovery.

A surge of b-phenylethylamine (PEA), an endogenous monoamine found in traces in the human brain and naturally present in chocolate, has been commonly associated with romantic love earning it the nickname of “love molecule”. The origin of this association must be traced to a speculation dating back to the early eighties that has over time become something of a factoid, reaching a large diffusion through the sharing phenomenon of the Internet. What is disputed in this paper is the existence of any direct biochemical or physiological evidence of the role of PEA in any of the phases of romantic love in the human species. The actual and possible roles of PEA in human physiology are reviewed.