Recently we demonstrated that both direct excitation of neurons and disinhibition in the pre-Bötzinger (pre-Böt) complex evoke an augmented or gasp-like pattern in the phrenic neurogram. To determine whether, after disinhibition, direct excitation of neurons in this region increases the occurrence of gasp-like activity, we examined the effects of chemical stimulation before and after blockade of GABAA receptors in the pré-Bot complex in chloraloseanesthetized, vagotomized, paralyzed cats. Sites in the pré-Bot complex were selected on the basis that chemical stimulation using DL-homocysteic acid (DLH; 10 mM; 21 ni), a glutamate analog, produced a gasp-like pattern in the phrenic neurogram. Bicuculline (BIC; 4.5 mM; 42 nl) was microinjected, and 5-20 minutes later we repeated the DLH microinjection. Microinjection of BIC produced either a gasp-like (n=4) or augmented (n=4) pattern in the phrenic neurogram and decreased the frequency of phrenic activity. Both before and after BIC, DLH produced a series of high amplitude, short duration phrenic bursts lasting from 14-68 s. DLH decreased Ti from 1.4±0.2 to 0.3±0.02 s before and from 1.8±0.5 to 0.7±0.1 s after BIC, and increased frequency of gasping by 145% (from 20±2 to 49±7 bursts per minute) before and by 146% (from 11±4 to 27±5 bursts per minute) after BIC. These findings suggest that, with or without disinhibition, direct excitation of neurons in the pre-Bot complex enhances expression of gasp-like activity. Support: HL16022. AHA/NJ Affiliate.
|Original language||English (US)|
|State||Published - 1996|
All Science Journal Classification (ASJC) codes
- Molecular Biology