Figure 5: Lactotroph network displays evolved behaviour and output following repeat stimulus.

(a) Functional connectivity (FC) map shows that connection distribution is similar in multiparas and primiparas (top panel). Middle panels show representative Ca²⁺ traces in lactotrophs of multiparas (second lactation; MP) with spontaneous Ca2+-spiking activity in lactotrophs identical to that observed in primiparas (AU, arbitrary unit), and a raster plot shows regular Ca2+ spiking that is distributed homogeneously over time at the population level. Distinct peaks of cell–cell coactivity are observed due to emergence of synchrony (*=peak of coactivity over a 95% significance threshold; bottom panel). (b) Probability histogram of intercoactivity intervals for primiparas (top panel) and multiparas (bottom panel). Note that peaks of coactivity due to cell synchrony are only observed in multiparas, as demonstrated by a Gaussian distribution of intercoactivity intervals centred on 115s (n=16–19 slices from at least six animals). (c) Probability histogram of intercoactivity intervals for multiparas exposed to Control and 18-alpha-glycerrhitinic acid (AGA) 20 μM. GJ blockade with AGA results in reversion to a primipara intercoactivity interval distribution due to abolition of cell synchrony (n=8 slices from three animals). (d) Probability histogram of intercoactivity intervals for multiparas suckled by a reduced number of pups during the first lactation. Prior exposure to a reduced suckling stimulus disrupts appearance of coactivity peaks in multiparas as shown by a non-Gaussian distribution of intercoactivity intervals (n=13 slices from five animals). (e) Tissue output in the form of prolactin (PRL) secretion markedly increases as a function of lactational experience (**P<0.01 versus nullipara (NP), ^##P<0.01 versus primipara (PP); Kruskal–Wallis test) and this can be reversed by exposing multiparas to reduced demand during the first lactation (NS, nonsignificant versus PP; Kruskal–Wallis test; n=6–19 animals). Values represent mean±s.e.m.±