ONTOGENESIS AND REGIONAL DISTRIBUTION OF HISTAMINE AND HISTAMINE‐N‐METHYLTRANSFERASE IN THE GUINEA PIG BRAIN¹

Abstract

Abstract— The ontogenetic development and the regional distribution of histamine (HA) and histamine‐N‐methyltransferase (HMT, EC 2.1.1.8) in guinea pig brain and pituitary gland were studied. The samples were taken every fourth day beginning on the 28th foetal day. The HA concentration in the brains of the youngest foetuses was almost undetectable. A significant increase in HA concentrations occurred between days 40 and 44, which coincides with the period of rapid growth of nerve cell processes in this species. After this, a steep increase continued to the end of gestation in the hypothalamus, and to a lesser degree in the medulla‐midbrain and in the forebrain. In all parts of the brain the adult HA levels were reached by the time of birth. The HMT activity increased 15‐fold from the 28th foetal day to the adult and reached ca. 80% of the adult activity by the time of birth. The HMT activity developed earlier in the midbrain than in the forebrain or in the cerebellum, but after the birth the regional distribution of HMT was fairly even. In the pituitary gland the HA concentration and HMT activity increased hundredfold and tenfold, respectively. The developmental patterns of HA and HMT in the guinea pig brain give support to the concept that HA might be a neurotransmitter in the brain.

Neuronal and vascular localization of histamine N‐methyltransferase in the bovine central nervous system

“…However, the activity of HMT was lowest in the bovine hypothalamus, which showed a remarkable contrast with the highest histidine decarboxylase activity in this region. A relatively high HMT activity was observed in the cerebellum and midbrain compared with those in the rat (Garbarg et al, 1973;Saavedra et al, 1976) and guinea-pig brains (Tuomisto, 1977). Inconsistency in the distribution of HMT activity with those of histidine decarboxylase activity or histamine content strongly suggests that the histaminergic cell bodies do not contain much HMT and that cells other than histaminergic neurons show large levels of HMT activity as estimated in the rat brain (Bischoff & Korf, 1978;Schwartz et al, 1991).…”

“…1973; Saavedra et al . 1976) and guinea‐pig brains (Tuomisto 1977). Inconsistency in the distribution of HMT activity with those of histidine decarboxylase activity or histamine content strongly suggests that the histaminergic cell bodies do not contain much HMT and that cells other than histaminergic neurons show large levels of HMT activity as estimated in the rat brain (Bischoff & Korf 1978; Schwartz et al .…”

Ontogeny of Histaminergic Neurotransmission in the Rat Brain: Concomitant Development of Neuronal Histamine, H‐1 Receptors, and H‐1 Receptor‐Mediated Stimulation of Phospholipid Turnover

“…Relative contributions of neuronal and non-neuronal his- tamine may also explain species differences in ontogeny of histamine levels. In the guinea pig, where mast cells are few and where synaptogenesis generally occurs earlier (in ufero), the hypothalamic histamine level rises earlier than in the rat and the developmental patterns show regional differences in magnitude but not in direction (i.e., all regions show developmental increases) (Tuomisto, 1977). Thus, it is apparent that, in the rat, assessment of histamine levels alone may be inadequate in evaluating ontogeny of histaminergic pathways.…”

Histamine and histamine-N-methyltransferase in the goat brain

“…The HMT activity in the goat brain was about one-third of that in the guinea pig brain, as assayed by an identical method [12], and there was little variation between various parts of the brain. So far there is no explanation for the higher enzyme activity in the pineal glands of the young goats compared to the older ones.…”

“…Some samples were taken from conscious goats without any drugs and serial post-mortem samples after an overdose of pentobarbital. HA and HMT were measured, using the radioenzymatic micromethod of TAYLOR and SN'COER [11] with some modifications [12]. Protein was assayed with the BioRad protein assay kit.…”