 Iain J. Clarke

Iain J. Clarke is a physiologist whose work investigates how brain signals regulate reproduction and other body functions. His Monash profile identifies research in reproduction, the hypothalamus and large-animal models.^[ref]

With James T. Cummins, he developed experiments that directly compared hormone signals and pituitary responses. After the portal-sampling work, a 1985 study used ewes whose pituitaries had been surgically disconnected from hypothalamic input. The investigators supplied controlled GnRH pulses and measured LH responses. Animals receiving a fixed-size pulse every two hours had larger individual LH responses than animals receiving it hourly; a later infusion tested the releasable pituitary hormone pool.^[ref]

The design makes timing an explicit experimental variable. With $250\mathrm{ng}$ per pulse, an hourly schedule delivers $6\mu \mathrm{g}$ per day, while a two-hour schedule delivers $3\mu \mathrm{g}$. Thus changing frequency at fixed pulse size also changes total input; that distinction belongs in the interpretation. The resulting work connects a hormone's temporal pattern with the response and storage capacity of its target organ.