QUANTITATIVE REEVALUATION OF THE EFFECTS OF SHORT- AND LONG-TERM REMOVAL OF DESCENDING MODULATORY INPUTS ON THE PYLORIC RHYTHM OF THE CRAB,CANCER BOREALIS.
The crustacean stomatogastric ganglion (STG) receives descending neuromodulatory inputs from three anterior ganglia, the paired commissural ganglia (CoGs) and the single esophageal ganglion (OG). In this paper we provide the first detailed and quantitative analyses of the short- and long-term effects of removal of these descending inputs (decentralization) on the pyloric rhythm of the STG. Thirty minutes after decentralization, the mean frequency of the pyloric rhythm dropped from 1.20 Hz in control to 0.52 Hz. Whereas the relative phase of pyloric neuron activity was approximately constant across frequency in the controls, after decentralization this changed markedly. Nine control preparations kept for 5-6 daysin vitromaintained pyloric rhythm frequencies close to their control values. Nineteen decentralized preparations kept for 5-6 days dropped slightly in frequency from those seen at 30 minutes after decentralization, but then displayed stable activity over 6 days. Bouts of higher frequency activity were intermittently seen in both control and decentralized preparations, but the bouts began earlier and were more frequent in the decentralized preparations. Although the bouts may indicate that the removal of the modulatory inputs triggered changes in neuronal excitability, these changes did not produce obvious long-lasting changes in the frequency of the decentralized preparations.
Volen Center and Biology Department (all authors), M.S. 013, Brandeis University, Waltham, MA 02545 USA.
Albert W
AW
Hamood
Volen Center and Biology Department (all authors), M.S. 013, Brandeis University, Waltham, MA 02545 USA.
Sara A
SA
Haddad
Volen Center and Biology Department (all authors), M.S. 013, Brandeis University, Waltham, MA 02545 USA.
Adriane G
AG
Otopalik
Volen Center and Biology Department (all authors), M.S. 013, Brandeis University, Waltham, MA 02545 USA.
Philipp
P
Rosenbaum
Volen Center and Biology Department (all authors), M.S. 013, Brandeis University, Waltham, MA 02545 USA.
Eve
E
Marder
central pattern generators; homeostatic regulation of excitability; stomatogastric nervous system