Electrophysiological recording of hypothalamic brain regions in vivo using the transpharyngeal surgical approach in the rat.

Transpharyngeal (ventral) surgery in urethane-anaesthetised rats allows in vivo electrophysiological recording and/or imaging from superficial hypothalamic brain regions and from the pituitary gland. This surgical approach leaves the whole brain intact, providing a stable platform to study single or multiple identified cells over several hours with all central and peripheral inputs intact and the endocrine system functioning, which allows repeated drug application and stimulation of afferent inputs, as has been done for the arcuate nucleus, organum vasculosum of the lamina terminalis (OVLT) and suprachiasmatic nucleus (SCN) inputs to the supraoptic nucleus (SON). Exposing the ventral surface of the brain also allows simultaneous microdialysis for drug administration directly into the SON and for the collection of dialysate samples for measurement of somatodendritic neuropeptide release without disruption of the brain parenchyma. The most recent development using transpharyngeal surgery is two-photon imaging from the vasculature of the ventral surface of the brain, which has given insight into how SON neuronal activity affects cerebral blood flow and has identified a previously unknown SCN to OVLT portal blood system. Here we provide a brief history of the development of transpharyngeal surgery in the rat, instructions to complete the surgery and suggestions for future studies, extrapolating from the most recent developments in its use.