An analgesic pathway from parvocellular oxytocin neurons to the periaqueductal gray in rats.

The hypothalamic neuropeptide oxytocin (OT) exerts prominent analgesic effects via central and peripheral action. However, the precise analgesic pathways recruited by OT are largely elusive. Here we discovered a subset of OT neurons whose projections preferentially terminate on OT receptor (OTR)-expressing neurons in the ventrolateral periaqueductal gray (vlPAG).

TRP channels and monoterpenes: Past and current leads on analgesic properties.

The activation of the transient receptor potential (TRP) channels expressed by sensory neurons is essential to the transduction of thermal and mechanical sensory information. In the setting of chronic inflammatory conditions, the activation of the melastatin family member 8 (TRPM8), the TRP vanilloid 1 (TRPV1), and the TRP ankyrin 1 (TRPA1) is correlated with pain hypersensitivity reactions. Monoterpenes, among which pulegone and menthol, a major class of phytocompounds present in essential oils of medicinal plants, are known modulators of those TRP channels activity.

Viral vectors for opto-electrode recording and photometry-based imaging of oxytocin neurons in anesthetized and socially interacting rats.

Here, we present a step-by-step protocol to target, record, and manipulate the activity of oxytocin neurons in awake rats. The protocol includes a procedure to record the activity of oxytocin neurons from awake and socially interacting rats using opto-electrodes for simultaneous electrophysiological recording and virally based cell-type-specific opto-tagging with Channelrhodopsin 2. Furthermore, we illustrate a procedure for optically guided implantation of optic fiber and imaging of oxytocin neuron population activity expressing calcium indicator GCaMP6s with the fiber photometry technique.