Hyperpolarisation-activated current in glomerular cells of the rat olfactory bulb

Whole-cell patch-clamp recordings were carried out in visually identified periglomerular and external tufted cells of rat olfactory bulb. Most of the neurones showed a slowly developing hyperpolarisation-activated current with a threshold generally positive to resting potential and with a strongly voltage-dependent activation time constant. The current, identified as Ih, was sodium- and potassium-sensitive, suppressed by external caesium, and insensitive to barium. Under current-clamp conditions, perfusion with caesium induced a 10 mV hyperpolarisation and a marked reduction of the rate of low-frequency oscillations induced experimentally. It is concluded that most of the cells in the rat glomerular layer present a distinct h-current, which is tonically active at rest and which may contribute to the oscillatory behaviour of the bulbar network.