β‐adrenoceptor‐mediated facilitation of [³H]‐noradrenaline release from the intramural nerves of bovine mesenteric lymphatic vessels

Abstract

1 Isolated segments of bovine mesenteric lymphatic vessels were loaded with [3H]-noradrenaline and its efflux in response to field stimulation at 2 Hz (0.3 ms pulses, 1 min train) examined. 2 Isoprenaline (10-6M) increased evoked fractional 3H efflux (3H released as a percentage of total tissue 3H at the onset of stimulation) from its control value of 0.67 + 0.09 to 1.2 + 0.18% (s.e.mean; n = 5).3 Propranolol (10-6 M) alone had no effect on evoked fractional 3H efflux but blocked the increase in transmitter overflow induced by isoprenaline (10-6 M). 4 In the presence of the a-adrenoceptor antagonist phentolamine (10 6M) the facilitatory effect of isoprenaline (10-6M) on transmitter efflux was enhanced. In 5 experiments isoprenaline increased evoked fractional 3H efflux from its control value of 1.07 + 0.17 to 2.5 + 0.37% when phentolamine was present.5 Adrenaline (10-8M) increased evoked fractional 3H efflux from its control value of 0.76 + 0.09 to 1.13 + 0.17% (n = 7). 6 These findings are consistent with the presence of presynaptic fi-adrenoceptors in this preparation. There is no evidence that these receptors play any role in feedback regulation of transmitter release.

Chronic stress in mice remodels lymph vasculature to promote tumour cell dissemination

“…In contrast, the data presented here suggest that PGE2 derived from TAMs may contribute to stress regulation of tumour cell-derived VEGFC. In addition, it will be important to define the direct effect of stress on lymphatic vasculature function, as isolated lymphatic vessels have been shown to respond to β-agonists 63 . Further studies using strategies such as cell-specific knockout will be required to assess the effect of β-adrenergic signalling on these various cell populations and determine their respective contributions to remodelling of lymphatic vasculature.…”

Lymphatic Innervation

“…Oi-Antagonists were also inef fective at blocking the postsynaptic response to field stimulation unlike a 2-antagonists which were effective suggesting that the 0 2-subtype predominates in lymphatic smooth muscle. Isoprenaline potentiated [3H]-efflux suggesting that a facilitatory presynaptic reg ulatory mechanism also exists [12].…”