Differential effects of salvinorin A on endotoxin‐induced hypermotility and neurogenic ion transport in mouse ileum

Background Salvinorin A (SA) is the principal active ingredient of Salvia divinorum, with an established inhibitory action on gastrointestinal (GI) transit and colonic ion transport in mice. Under normal conditions, the effects of SA are mediated by kappa opioid (KOR) and cannabinoid (CB1 and CB2) receptors. However, the role of SA in pathophysiological conditions remains unresolved. The aim of this study was to characterize the in vitro and in vivo effects of SA on mouse ileum after endotoxin challenge. Methods Changes in GI motility were studied in vitro, using smooth muscle preparations from the mouse ileum. In vivo, the fecal pellet output and small intestinal fluid content were measured. Neurogenic ion transport and intestinal permeability were examined using Ussing chambers. In addition, Western blot analysis of mucosa was performed and plasma nitrite/nitrate levels were determined. Key Results Salvinorin A inhibited endotoxin‐induced ileal hypercontractility via KOR, CB1, and CB2 receptors. Neurogenic ion transport, which was significantly reduced after endotoxin challenge, was normalized by SA through a nitric oxide synthase (NOS)‐dependent mechanism. Western blot analysis and plasma nitrite/nitrate level quantitation confirmed the involvement of NOS in the regulatory action of SA. Conclusions & Inferences This is the first report showing differential effects of SA on motor and secretory activity in mouse GI during endotoxemia. The outcomes of our study imply possible novel applications of SA and its analogs in the treatment of GI disorders.     

The hallucinogenic herb Salvia divinorum and its active ingredient salvinorin A inhibit enteric cholinergic transmission in the guinea-pig ileum.

Salvia divinorum is a widespread hallucinogenic herb traditionally employed for divination, as well as a medicament for several disorders including disturbances of gastrointestinal motility. In the present study we evaluated the effect of a standardized extract from the leaves of S. divinorum (SDE) on enteric cholinergic transmission in the guinea-pig ileum. SDE reduced electrically evoked contractions without modifying the contractions elicited by exogenous acetylcholine, thus suggesting a prejunctional site of action. The inhibitory effect of SDE on twitch response was abolished by the opioid receptor antagonist naloxone and by the kappa-opioid antagonist nor-binaltorphimine, but not by naltrindole (a delta-opioid receptor antagonist), CTOP (a mu-opioid receptor antagonist), thioperamide (a H(3) receptor antagonist), yohimbine (an alpha(2)-receptor antagonist), methysergide (a 5-hydroxytryptamine receptor antagonist), N(G)-nitro-L-arginine methyl ester (an inhibitor of NO synthase) or apamin (a blocker of Ca(2+)-activated K(+) channels). Salvinorin A, the main active ingredient of S. divinorum, inhibited in a nor-binaltorphimine- and naloxone-sensitive manner electrically induced contractions. It is concluded that SDE depressed enteric cholinergic transmission likely through activation of kappa-opioid receptors and this may provide the pharmacological basis underlying its traditional antidiarrhoeal use. Salvinorin A might be the chemical ingredient responsible for this activity.     

Increase of morphine withdrawal in mice lacking A2a receptors and no changes in CB1/A2a double knockout mice

CB1 cannabinoid and A2a adenosine receptors are highly expressed in the central nervous system where they modulate numerous physiological processes including emotional behaviour and the responses of several drugs of abuse. To investigate the contribution of these receptors in emotional-like responses and opioid dependence we have generated CB1/A2a double deficient mice (CB1-/-/A2a-/-). The spontaneous locomotor activity was reduced in double knockout as compared to wild-type animals. Emotional-like responses of CB1-/-/A2a-/- mice were investigated using the elevated plus-maze and the lit-dark box. Mutant mice exhibited an increased level of anxiety in both behavioural models. The specific involvement of CB1 and A2a receptors in morphine dependence was evaluated by using A2a knockout mice and CB1/A2a double mutant mice. The severity of naloxone-precipitated morphine withdrawal syndrome was significantly increased in the absence of A2a adenosine receptors whereas no modifications were observed in the double knockout mice. These results suggest that both receptors participate in the control of emotional behaviour and seem to play an opposite role in the expression of opioid physical dependence.     

Therapeutic-like activity of cannabidiolic acid methyl ester in the MK-801 mouse model of schizophrenia: Role for cannabinoid CB1 and serotonin-1A receptors

Schizophrenia is a psychotic disorder with an increasing prevalence and incidence over the last two decades. The condition presents with a diverse array of positive, negative, and cognitive impairments. Conventional treatments often yield unsatisfactory outcomes, especially with negative symptoms. We investigated the role of prefrontocortical (PFC) N-methyl-D-aspartate receptors (NMDARs) in the pathophysiology and development of schizophrenia. We explored the potential therapeutic effects of cannabidiolic acid (CBDA) methyl ester (HU-580), an analogue of CBDA known to act as an agonist of the serotonin-1A receptor (5-HT1AR) and an antagonist of cannabinoid type 1 receptor (CB1R). C57BL/6 mice were intraperitoneally administered the NMDAR antagonist, dizocilpine (MK-801, .3 mg/kg) once daily for 17 days. After 7 days, they were concurrently given HU-580 (.01 or .05 μg/kg) for 10 days. Behavioural deficits were assessed at two time points. We conducted enzyme-linked immunosorbent assays to measure the concentration of PFC 5-HT1AR and CB1R. We found that MK-801 effectively induced schizophrenia-related behaviours including hyperactivity, social withdrawal, increased forced swim immobility, and cognitive deficits. We discovered that low-dose HU-580 (.01 μg/kg), but not the high dose (.05 μg/kg), attenuated hyperactivity, forced swim immobility and cognitive deficits, particularly in female mice. Our results revealed that MK-801 downregulated both CB1R and 5-HT1AR, an effect that was blocked by both low- and high-dose HU-580. This study sheds light on the potential antipsychotic properties of HU-580, particularly in the context of NMDAR-induced dysfunction. Our findings could contribute significantly to our understanding of schizophrenia pathophysiology and offer a promising avenue for exploring the therapeutic potential of HU-580 and related compounds in alleviating symptoms.