The inhibition of insulin secretion in sheep exposed to cold has been reported to be mediated through adrenergic α receptors stimulated by sympathoadrenomedullary activity (Sasaki and Takahashi, 1980). Insulin secretion in Holstein non-lactating cows in response to various secretogogues was also suppressed during heat exposure (Itoh et al., unpublished data), however it is not obvious whether these responses were related to neural controls or not. However acetylcholine (parasympathetic nervous system neurotransmitter) has been shown to promote the release of glucagon and insulin (Jones et al., 1991). Therefore, the objective of this study was to examine the participation of adrenergic and cholinergic neural control on insulin secretion in thermoneutral and hot environments in non-lactating cows by administering, adrenergic and cholinergic blockers with an intravenous injection of glucose.