Neuronal responses to delta 9-tetrahydrocannabinol in the solitary tract nucleus.

The effects of delta 9-tetrahydrocannabinol on single-unit activity in the subpostremal division of the nucleus tractus solitarii were investigated by extracellular recording in rat brain slices. The spontaneous firing rate of 54.8% of the recorded neurons was significantly changed after bath applications of delta 9-tetrahydrocannabinol. Putative nutrition-related neurons responding to a moderate increase in glucose concentration were selectively sensitive to delta 9-tetrahydrocannabinol. The delta 9-tetrahydrocannabinol-sensitive neurons were depressed by clonidine and are therefore likely to be adrenergic or noradrenergic. These observations suggest that some catecholaminergic, glucose-responsive neurons in the subpostremal nucleus tractus solitarii might mediate the influence of cannabinoids on feeding behaviour. Furthermore, most delta 9-tetrahydrocannabinol-sensitive neurons in the nucleus tractus solitarii showed opposite responses to delta 9-tetrahydrocannabinol and the 5-HT3 receptor agonist 1-phenylbiguanide, and might therefore be involved in the nausea-reducing effects of cannabinoids.