Figure 5  .

The alpha adrenergic blocking drug, phentolamine, blocked both the hyperpolarising responses to micropressure application of norepinephrine (noradrenaline) and stimulus evoked inhibitory postsynaptic potentials (IPSP). (A) Micropressure ("spritz") application of 10 µM norepinephrine evoked a hyperpolarising response accompanied by decreased input resistance. Decreased input resistance was reflected by decreased amplitude of electrotonic potentials produced by intrasomal injection of constant current depolarising pulses. (B) Blockade of norepinephrine evoked response by phentolamine. (C) The neurone in A and B had uniaxonal morphology. (D) Focal electrical stimulation of an interganglionic connective evoked and IPSP. (E) Blockade of the IPSP by phentolamine. (F) Reversal of phentolamine induced blockade following washout of the drug. (G) The neurone in D and F had uniaxonal morphology.