The Regulation Of Respiration In Rat By Hippocampus And The Effects Of Ca～(2+) On The Respiratory Inhibition Induced By Opioids

The present study regards: (1) a role of hippocampus on the respiratory regulation in rat and its response to microinjected opioids; (2) the modulation of opioids -induced respiratory inhibition by Ca²⁺ and calcium channel antagonists; (3) the effects of Ca²⁺ on the inhibitory effect of opioids on the spontaneous and induced discharges of respiratory neurones in nucleus ambiguus; and (4) the effects of opioid receptor agonists on intracellular free calcium. The results are as follows:1. Respiratory changes induced by electircal and chemical stimulation of ventral hippocampusElectrical (15 s trains of 0.25 ms pulses at 50 Hz, 4 V) stimulation at the ventral hippocampus evoked inhibitory, facilitatory, or altering effects in phrenic nerve discharges. In the 80 points stimulated, 28 of which showed depression were located mainly in the caudal ventral hippocampus. Phrenic nerve discharges decreased 22.2±2.6%. The 38 points which showed excitation were found in...