Electrophysiology of identified neurosecretory and non-neurosecretory cells in the cockroach pars intercerebralis

✍ Scribed by Krauthamer, Victor

• Publisher: John Wiley and Sons
• Year: 1985
• Tongue: English
• Weight: 1016 KB
• Volume: 234
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/jez.1402340206

✦ Synopsis

Two cell types can be distinguished with intracellular recording from the pars intercerebralis of the American cockroach (Periplaneta arnericana). The first type, which corresponds morphologically to the medial neurosecretory cell, always had spontaneously occurring, overshooting action potentials. These action potentials are probably endogenously produced. Tetrodotoxin experiments revealed that sodium is the dominant ion of the action potential. The action potentials are followed by a relatively long after-hyperpolarization. The input resistance of these cells ranged from 120 to 390 MQ. A mathematical model, based on cellular morphology and response to current pulses, revealed a membrane time constant of about 100 msec and an ax-ona1:somatic conductance ratio of approximately 13. Area-specific membrane resistance was estimated at 33 kQ cm2. These cells also often had reversible and spontaneous inhibitory postsynaptic potentials. The second cell type, which is non-neurosecretory, never produced spontaneous action potentials and rarely had synaptic potentials. Action potentials could be evoked by current injection into the cell body or by extracellular stimulation of their axons in the posteroventral portion of the the protocerebrum. These action potentials also depend on sodium ions. Their input resistance ranged from 16 to 35 MQ. They had a membrane time constant of approximately 15 msec and an axona1:somatic conductance ratio of about 9. Their area specific membrane resistance was estimated at 14 kQ cm2.