Hemopressin Peptides and WIN Showed Symmetrical Cross-Tolerance After Direct Brain Administration in Mice
A mouse study found antinociceptive tolerance and symmetrical cross-tolerance among hemopressin, VD-hemopressin alpha and WIN55,212-2. The finding applies to direct supraspinal administration and a thermal response, rather than every effect of these ligands.
The ligands carried different pharmacological descriptions
Hemopressin had been characterized as a CB1 antagonist or inverse agonist, while its extended peptide was described as an agonist. Nevertheless, hemopressin produced dose-dependent antinociception after intracerebroventricular administration. A receptor label alone did not settle its observed effect in this protocol.
Repeated exposure reduced the response
Tolerance developed by the fourth treatment day for each of the three ligands. Cross-challenges showed symmetrical cross-tolerance among them on the radiant-heat tail-flick measure. This supports overlap in adaptation under the tested conditions without demonstrating identical molecular actions.
A common mechanism was an inference
The authors interpreted the shared pattern as implying a common antinociceptive mechanism. Cross-tolerance alone cannot specify every receptor interaction or exclude downstream convergence. Nor does symmetry on one thermal endpoint imply symmetry for temperature, movement, reward or other functions.
The study adds an experimentally defined relationship between cannabinoid-related peptides and a synthetic agonist. Direct brain administration and mouse antinociception sharply limit clinical translation. It does not establish oral efficacy, human safety or a method of predicting cannabis impairment.
Related: interpreting cannabis tolerance claims.
Research cited
Pan JX; Wang ZL; Li N; Han ZL; Li XH; Tang HH; Wang P; Zheng T; Fang Q; Wang R. Analgesic tolerance and cross-tolerance to the cannabinoid receptors ligands hemopressin, VD-hemopressin(α) and WIN55,212-2 at the supraspinal level in mice. Neuroscience letters (2014). doi:10.1016/j.neulet.2014.06.058. Findings discussed from the study abstract.
