Chronic food restriction alters mu and kappa opioid receptor binding in the parabrachial nucleus of the rat: a quantitative autoradiographic study.

Using quantitative autoradiography, it was previously observed that chronic food restriction alters mu and kappa receptor binding in several regions of the rat forebrain. The present autoradiographic study was designed to investigate whether food restriction affects regional mu and kappa binding in the brainstem. [3H]DAGO (mu) and-mu/delta blocked [3H]BMZ (kappa) binding were analyzed in 21 brainstem regions. A significant decrease in mu binding was observed in the external lateral and external medial subnuclei of the parabrachial nucleus while a significant increase in kappa binding was observed in the external lateral subnucleus. The possible functional significance of these changes is discussed.