Brain transections selectively alter ingestion and behavioral activation in neonatal rats.

Abstract

Pood-deprived neonatal rats actively ingest milk that is infused into their mouths through intraoral cannulas. This ingestion is accompanied by behavioral activation. The involvement of various brain regions in ingestion and activation was examined by making transections along the neuraxis from ;the olfactory bulbs to the anterior pons in 2-day-old rats. Following a 24-hr deprivation period, a series of oral milk infusions was given, and milk intake and activity were measured. Intake was severely reduced only in animals with diencephalic transections. Cuts in front of or behind the diencephalon resulted in normal or slightly decreased intake. In contrast, activity tended to decline as the level of the transection became more caudal. Thus ingestion and its accompanying behavioral activation could be separated neuroanatomically. These results suggest that two brain mechanisms are involved in the ingestive response of the infant rat, one in the diencephalon and another caudal to the mesencephalon. However, behavioral activation appears less discretely organized, involving most of the neuraxis.

Ontogeny of ingestive behavior

“…This has been shown as early as P2 (Kornblith & Hall, 1979) and it is consistent with the results of OC infusions in chronic decerebrate, adult rats (Grill & Smith, 1988). Rinaman has called attention to the heuristic parallels between the immaturity of ascending and descending connections of the forebrain and hindbrain in the pup and the lesion of the mature connections by chronic decerebration in the adult rat (see her article).…”

Kinematic analyses of air-stepping in normal and decerebrate preweanling rats

“…For example, it has been shown that much of the ingestive behavior of the infant rat is organized in the brainstem (Kornblith & Hall, 1979;Swithers Mulvey & Hall, 1993), as is a major component in the control of brown adipose tissue thermogenesis (Bignall, Heggeness, & Palmer, 1975). The righting reflex of neonatal rats is organized caudally in the brainstem, with more rostral controls exerting a modulating influence with increasing maturation (Bignall, 1974).…”

Cardiac orienting and habituation to auditory and vibrotactile stimuli in the infant decerebrate rat

“…Decerebrate animals were more difficult to feed, however, and the body weights of these animals were lower than those of normal subjects. (Kornblith & Hall, 1979). An Age X Surgical condition ANOVA of these scores revealed a main effect of Surgical condition (F(1,26) = 5 .…”

“…Unfortunately, the infant decerebrate preparation has received relatively little experimental attention. The available literature, however, suggests that with the exception of feeding behavior, decerebrated infant animals develop within nearly normal limits along both physical and behavioral dimensions (Bignall, 1974;Bignall & Schramm, 1974;Kornblith & Hall, 1979;Langworthy, 1929;Thexton & Griffith, 1979;Weed, 1917). In the only existing report of habituation in the infant decerebrate rat, Campbell and Stehouwer (1 979) have documented the normal development of habituation processes in animals decerebrated within 10 days of birth, while habituation was retarded in rats decerebrated at 15 or 20 days of age.…”