Abstract: Synthetic cannabinoids (SCs) are synthetic psychoactive substances that can pose a public health risk. The SCs are structurally variable and susceptible to structural modification. The rapid emergence of structurally unknown synthetic cannabinoids has led to new challenges in their identification. In recent years, machine learning has made great progress and has been widely applied to other fields, providing new strategies for the identification of unknown synthetic cannabinoids and the inference of possible sources. This paper describes the principles of commonly used machine learning methods and the application of machine learning techniques to mass spectrometry, Raman spectroscopy, metabolomics and quantitative conformational relationships of synthetic cannabinoids, aiming to provide new ideas for the identification of unknown synthetic cannabinoids.

The nucleus tractus solitarii (NTS) is one of the morphologically and functionally defined centers that engage in the autonomic regulation of cardiovascular activity. Phenotypically-characterized NTS neurons have been implicated in the differential regulation of blood pressure (BP). Here, we investigated whether phenylethanolamine N-methyltransferase (PNMT)-expressing NTS (NTS^PNMT) neurons contribute to the control of BP. We demonstrate that photostimulation of NTS^PNMT neurons has variable effects on BP. A depressor response was produced during optogenetic stimulation of NTS^PNMT neurons projecting to the paraventricular nucleus of the hypothalamus, lateral parabrachial nucleus, and caudal ventrolateral medulla. Conversely, photostimulation of NTS^PNMT neurons projecting to the rostral ventrolateral medulla produced a robust pressor response and bradycardia. In addition, genetic ablation of both NTS^PNMT neurons and those projecting to the rostral ventrolateral medulla impaired the arterial baroreflex. Overall, we revealed the neuronal phenotype- and circuit-specific mechanisms underlying the contribution of NTS^PNMT neurons to the regulation of BP.
Solitary Nucleus/metabolism* ; Blood Pressure/physiology* ; Phenylethanolamine N-Methyltransferase/metabolism* ; Neurons/metabolism* ; Paraventricular Hypothalamic Nucleus/metabolism*