Respiratory reactions to microinjection of bombesin into the solitary tract nucleus and their mechanisms

Abstract

Acute experiments were performed on urethane-anesthetized adult laboratory rats to investigate the effects of microinjections of 10(-13)-10(-4) M bombesin into the solitary tract nucleus on measures of respiration. Bombesin microinjections were found to stimulate respiration, inducing significant increases in the level of pulmonary ventilation, increases in respiratory volume, and increases in the bioelectrical activity of the inspiratory muscles. The most marked respiratory reactions were seen after intermediate peptide doses (10(-10)-10(-7) M). These respiratory effects of bombesin were found to result from its ability to suppress the inspiration-inhibiting Hering-Breuer reflex at the level of the solitary tract nucleus. The fact that ultralow doses of bombesin were active, along with the distribution of endogenous bombesin and its specific receptors in the solitary tract nucleus, and the ability of this peptide to modulate the Hering-Breuer reflex all provide evidence that bombesin is involved in controlling respiration at the level of the dorsal structures of the respiratory center.

Intrathecal bombesin is sympathoexcitatory and pressor in rat

“…A study in urethane-anesthetised, nonvagotomized adult male Wistar rats also describes dose-dependent sSNA increase following intracerebroventricular bombesin (47). Key differences between this study and others that evaluated the effects of bombesin on breathing (22,25,26) are the route of administration and the use of direct recording of the phrenic nerve to determine central inspiratory activity. A common finding, here and in earlier studies, is the increase in respiratory amplitude and decrease in respiratory rate.…”

“…Centrally, moderate, to high bombesin immunoreactivity is found in neurons and fibers in the nucleus tractus solitarius (NTS), RVLM, CVLM, PVN, and spinal cord (11,35). NTS microinjection or intracerebroventricular bombesin potentiates respiration (22,26) and increases plasma catecholamines (6). Intracerebroventricular bombesin causes a reduction in sympathetic outflow to brown fat that is associated with hypothermia (4).…”

“…These peptides differentially affect sympathetic tone and adaptive reflexes. Previously, it was shown that bombesin has vasopressor actions and stimulates breathing when applied centrally or peripherally (15,22,25,26,30,31). Here we aimed to determine whether or not intrathecal bombesin exerts cardiorespiratory effects.…”

Blockade of Rostral Ventrolateral Medulla (RVLM) Bombesin Receptor Type 1 Decreases Blood Pressure and Sympathetic Activity in Anesthetized Spontaneously Hypertensive Rats

“…Zogovic and Pilowsky ( 2011 ), showed a long-lasting increase in the splanchnic SNA (sSNA), blood pressure and phrenic nerve amplitude by the intrathecal injection of BBS. Glazkova and Inyushkin ( 2006 ) reported that microinjection of BBS in the solitary tract nucleus (NTS) stimulated respiration, and increased the level of pulmonary ventilation, respiratory volume, and bioelectrical activity of the inspiratory muscles. Our results showed that BBS injected into the RVLM increased arterial blood pressure and sympathetic vasomotor tone in both NT and SHR.…”

“…In mammals, BBS receptors and BBS-like peptides are distributed in the Central Nervous System (CNS) (Woodruff et al, 1996 ; Jensen et al, 2008 ) including regions involved in the cardiorespiratory control (Chung et al, 1989 ; Lynn et al, 1996 ; Li et al, 2016 ). The administration of BBS has been reported to enhancebreathing (Holtman et al, 1983 ; Glazkova and Inyushkin, 2006 ), raise plasma concentration of catecholamine (Brown and Fisher, 1984 ), tachycardia (Zogovic and Pilowsky, 2011 ), increase blood pressure (Brown, 1983 ; Zogovic and Pilowsky, 2011 ), and sympathetic tone (Zogovic and Pilowsky, 2011 ) in normotensive (NT) rats. Zogovic and Pilowsky ( 2011 ) showed that intrathecal injection of BBS is associated with sympathoexcitatory and pressor responses.…”