Anti-stress Effect of Hypothalamic Oxytocin, Importance of Somatosensory Stimulation and Social Buffering

Abstract

A growing body of evidence suggests that stress stimuli, both acute and chronic, promote different physiological mechanisms and neuroendocrine responses. Oxytocin (OXT) is mainly synthesized in the paraventricular nucleus (PVN) and supraoptic nucleus (SON) of the hypothalamus. Central OXT has an anxiolytic effect and attenuates the hypothalamic-pituitary-adrenal (HPA) axis in response to stress. Anti-stress effect of OXT has been explained by its inhibitory effect on corticotropin releasing factor (CRF) expression at the PVN via GABAA receptors. Repeated experience with the same stressor produces habituation, or diminution of behavioral responses and HPA axis responses. Up-regulated OXT expression in the PVN is involved in mediating habituation in response to chronic homotypic stress in rats. In contrast to chronic homotypic stress, no habituation is observed when rats are singly housed and received different types of stressors for 7 days (chronic heterotypic stress). Increased CRF expression and reduced OXT expression at the PVN are observed following chronic heterotypic stress in singly housed rats. Thus, it is conceivable that stress responses to chronic heterotypic stress would be diminished if endogenous OXT expression is upregulated. Various manual therapies such as massage, acupuncture and transcutaneous electrical nerve stimulation (TENS) involve the stimulation of somatosensory neurons. OXT system is activated by manual therapies. TENS increases OXT expression and decreases CRF expression at the PVN following chronic heterotypic stress in singly housed rats. OXT has been implicated in a number of social behaviors, including maternal care, affiliation and social attachment. Social attachment is known to stimulate OXT release in the hypothalamus in rats. A recent study demonstrates an increased OXT expression following chronic heterotypic stress when rats are pair-housed. Somatosensory stimulation is a promising treatment for stress-associated diseases. A social interaction is also important to adapt to our daily life stress.

The Effects of Intranasal Oxytocin on Neural and Behavioral Responses to Social Touch in the Form of Massage

“…The sense of touch relies on the sensory and perceptual consequences of stimulation of low-threshold afferent fibers in the skin since these cutaneous afferents convey distinct sensory/perceptual qualities which are projected to different stimulus-specific neurons (McGlone et al, 2014). There are multiple types of nervous fibers that transmit cutaneous stimulation, including both fast conducting thick myelinated A-β afferents which subserve the discriminative perception of touch (i.e., the pressure, vibration, and texture) and thin unmyelinated low-conducting nerve receptors including C-and A-δ afferent fibers which are described as thermo-, noci-or chemoreceptive (Björnsdotter et al, 2010;McGlone et al, 2012McGlone et al, , 2014Takahashi et al, 2015). The low-threshold unmyelinated C-touch afferent fibers (or CT fibers), which selectively respond to gentle, slowly applied caress-like stroking on hairy skin (Ackerley et al, 2014;McGlone et al, 2014), are found to associate closely with pleasantness processing of social affective touch (Essick et al, 2010;Pawling et al, 2017) and increased activity in corresponding brain reward regions such as the orbitofrontal cortex (OFC) and other regions involved in social-affective processing such as the insula and the superior temporal sulcus (STS) (Olausson et al, 2010;Gordon et al, 2013;Björnsdotter et al, 2014;Croy et al, 2016;Morrison, 2016).…”

The Oxytocinergic System as a Mediator of Anti-stress and Instorative Effects Induced by Nature: The Calm and Connection Theory

“…These behaviors are linked to a sense of reward and relaxation and to a decrease of stress levels. Also bonding between the two individuals may be induced as a consequence of in particular repeated positive interaction ( Auyeung et al, 2015 ; Takahashi et al, 2015 ; Andari et al, 2016 ; Shamay-Tsoory and Abu-Akel, 2016 ; Pawling et al, 2017 ; Uvnäs-Moberg et al, 2020b ).…”

“…Sensory nerves are activated in response to physical touch, among those the CT afferents: an old type of sensory nerves, which are linked to the experience of wellbeing ( Pawling et al, 2017 ). Activation of the CT fibers and also of other types of nerves originating in the skin as well as auditory, visual, and olfactory stimuli contributes to the release of oxytocin induced as a consequence of social interaction between humans ( Takahashi et al, 2015 ).…”

“…Moreover, administration of oxytocin increases an individual's ability to interpret other individuals' facial language and tone of voice (Hollander et al, 2003(Hollander et al, , 2007Domes et al, 2014;Skuse et al, 2014), as well as body language (Kéri and Benedek, 2009). Oxytocin also increases the sensitivity to touch, and infusions of oxytocin have been shown to increase touch induced oxytocin release (Velandia, 2012), during positive interaction and thereby to the oxytocin mediated effects (Takahashi et al, 2015). Recently, studies demonstrating that oxytocin administration promotes social interaction, positive emotions, and reward have been extended to include brain studies using fMRI.…”

Oxytocin Release during the Meditation of Altruism and Appreciation (Arigato-Zen)

“…In addition, these impulses are also relayed to other brain areas, including hypothalamus, via collateral connections [38] . These raise the possibility that vocal sound-vibration of AZ may stimulate somatosensory pathway and spinal-supraspinal pathways (bottom-up pathway) [39] .…”