Figure 3.

Demonstration that systemically administered F792 does not interfere with the excitation of magnocellular paraventricular nucleus oxytocin neurones during suckling. (a) Instantaneous firing rate record of a single antidromically identified paraventricular nucleus oxytocin neurone in a urethane‐anaesthetised lactating rat with at least six pups suckling throughout. b1, b2 and b3 indicate three spontaneous milk‐ejection bursts, after which 100 μg of F792 was injected i.v., as shown by the orange arrow. b4 and b5 mark two subsequent milk‐ejection bursts, after which 2 mU of oxytocin was injected i.c.v., producing the expected facilitation of burst amplitude and frequency. The profiles of the two bursts before injection of F792 and the two bursts after are expanded below. (b) Comparison of milk‐ejection burst profiles before and after i.v. injection of 100 μg of F792. Blue dots are from the last spontaneous milk ejection before injection of F792, and the orange dots are from the first burst after that injection. The total number of spikes within 2 s from the start of the burst is indicated, as is the time elapsed after injection of F792. The three cells (in three different rats) displayed bursts of differing magnitudes and amplitudes but, in each case, the burst amplitude and profile was completely unaffected by F792 injection.