Tegmental neurons controlling medullary respiratory centre activity in the carp

The dorsal mesencephalic tegmentum of the carp was explored for respiratory rhythmic neurons. The properties of two types of neurons which could be distinguished on the grounds of their firing pattern and their behaviour during paralysis and electrical stimulation were analysed. One group is involved in the control of a special type of respiration called bout-respiration and besides influences the frequency of the respiratory rhythm. The other group can modulate the output of the motor neurons of the cranial respiratory muscles via a multiple central route. HRP injections revealed extensive connections between these tegmental respiratory neurons and the respiratory centres in the medulla oblongata.