Partial cloning of CB1 cDNA and CB1 mRNA changes in stress responses in the Solea solea

Endogenous cannabinoids, through the CB1 receptor, are involved in the control of several functions including stress responses. The aim of this study was to investigate the presence of cannabinoid receptor CB1 in the sole ovary by partial cloning of brain CB1 cDNA; in a stress paradigm of disturbance by handling, which consisted in catching, netting and hand-sorting, changes of CB1 mRNA were related with those of proopiomelanocortin (POMC) mRNA; the trend and timing of stress responses and adaptation were monitored by measuring plasma cortisol levels. We characterized two forms of CB1-like receptor, termed CB1A and CB1B. The two sole CB1 (both 799bp) share 76% identity in their cDNAs, and the deduced amino acid sequences are 80% identical. The handling stress induced a sustained increase in plasma cortisol levels 1h after the handling began and decreased to low levels 12h after initiation of handling, showing the same trend of ovarian POMC mRNA expression. In addition, while CB1A mRNA did not show any significant changes during handling stress, significantly lower levels of CB1B mRNA were found in stressed fish 1h after the beginning of handling, with CB1 expression increased 24h after stress induction, both in the ovary and brain. It can be concluded that endocannabinoid system is involved in the modulation of adaptive responses to environmental conditions.